Mybatis（二）

1 Mybatis映射文件--增删改查

POJO类

package cn.demo1;

import org.apache.ibatis.type.Alias;

/**
 * 描述：POJO
 */
@Alias("emp")
public class Employee {
    private Integer id;
    private String lastName;
    private String gender;
    private String email;

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    public String getGender() {
        return gender;
    }

    public void setGender(String gender) {
        this.gender = gender;
    }

    @Override
    public String toString() {
        return "Employee{" +
                "id=" + id +
                ", lastName='" + lastName + '\'' +
                ", gender='" + gender + '\'' +
                ", email='" + email + '\'' +
                '}';
    }
}

EmployeeMapper.xml

<?xml version="1.0" encoding="UTF-8" ?>
        <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="cn.demo1.IEmployeeDAO">
<!--
    namespace：命名空间  指定为接口的全类名
    id:唯一标识 和接口中的方法名相同
    resultType：返回值类型
-->
<select id="findById" parameterType="int" resultType="emp" databaseId="mysql">
    select id,last_name,email,gender from employee where id = #{id}
</select>

<insert id="addEmployee" parameterType="cn.demo1.Employee">
    insert into employee(last_name,email,gender) values (#{lastName},#{email},#{gender})
</insert>

<update id="updateEmployee" parameterType="cn.demo1.Employee">
    update employee set last_name = #{lastName} ,email = #{email},gender = #{gender} where id = #{id}
</update>

<delete id="deleteEmployeeById" parameterType="java.lang.Integer">
    delete from employee where id = #{id}
</delete>

</mapper>

IEmployeeDAO

package cn.demo1;

public interface IEmployeeDAO {
    public Employee findById(Integer id);

    public void addEmployee(Employee employee);

    public void updateEmployee(Employee employee);

    public void deleteEmployeeById(Integer id);
}

配置文件--log4j.properties

### direct log messages to stdout ###
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.Target=System.err
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%d{ABSOLUTE} %5p %c{1}:%L - %m%n

### direct messages to file mylog.log ###
log4j.appender.file=org.apache.log4j.FileAppender
log4j.appender.file.File=c\:mylog.log
log4j.appender.file.layout=org.apache.log4j.PatternLayout
log4j.appender.file.layout.ConversionPattern=%d{ABSOLUTE} %5p %c{1}:%L - %m%n

### set log levels - for more verbose logging change 'info' to 'debug' ###

log4j.rootLogger=debug, stdout

配置文件--db.properties

jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/mybatis
jdbc.user=root
jdbc.password=root

配置文件--mybatis-config.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>

    <!--
        Mybatis可以使用properties属性来引入外部properties配置文件内容
            resource:引入类路径下的资源
            url:引入网络路径或磁盘路径下的资源
    -->
    <properties resource="db.properties"></properties>

    <settings>
        <!--
            是否开启自动驼峰规则映射，即如果数据表中的字段是last_name到Java中的lastName等类似的映射
         -->
        <setting name="mapUnderscoreToCamelCase" value="true"/>
    </settings>

    <!--
        typeAliases:别名处理器，可以为Java类型起别名
    -->
    <typeAliases>
        <!--
            类很多情况下，可以批量设置别名这个包下的每一个类创建一个默认的别名，就是简单类名小写。
        -->
       <package name="cn.demo1"/>
    </typeAliases>

    <!--
        environments ，Mybatis可以配置多种环境
            environment，配置一个具体的环境信息，必须有两个标签，ID表示当前环境的唯一标识
                transactionManager s事务管理器
                    type 事务管理器的类型
                        JDBC   this.typeAliasRegistry.registerAlias("JDBC", JdbcTransactionFactory.class);
                        MANAGER  this.typeAliasRegistry.registerAlias("MANAGED", ManagedTransactionFactory.class);
                dataSource
                        JNDI    this.typeAliasRegistry.registerAlias("JNDI", JndiDataSourceFactory.class);
                        POOLED  this.typeAliasRegistry.registerAlias("POOLED", PooledDataSourceFactory.class);
                        UNPOOLED  this.typeAliasRegistry.registerAlias("UNPOOLED", UnpooledDataSourceFactory.class);
    -->
    <environments default="mysql_development">
        <environment id="mysql_development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${jdbc.driver}"/>
                <property name="url" value="${jdbc.url}"/>
                <property name="username" value="${jdbc.user}"/>
                <property name="password" value="${jdbc.password}"/>
            </dataSource>
        </environment>
        <environment id="oracle_development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${oracle.driver}"/>
                <property name="url" value="${oracle.url}"/>
                <property name="username" value="${oracle.user}"/>
                <property name="password" value="${oracle.password}"/>
            </dataSource>
        </environment>
    </environments>

    <databaseIdProvider type="DB_VENDOR">
        <property name="MySQL" value="mysql"/>
        <property name="Oracle" value="oracle"/>
        <property name="SQL Server" value="sqlserver"/>
    </databaseIdProvider>

    <mappers>
        <mapper resource="cn/demo1/EmployeeMapper.xml"/>
    </mappers>
</configuration>

测试类

package cn.test;

import cn.demo1.Employee;
import cn.demo1.IEmployeeDAO;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Test;

import java.io.IOException;
import java.io.InputStream;

/**
 *
 * 描述：
 */

public class MybatisTest {
    /**
     * 测试查询
     * @throws IOException
     */
    @Test
    public  void demo1() throws IOException {
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        SqlSession session = sqlSessionFactory.openSession();

        IEmployeeDAO dao = session.getMapper(IEmployeeDAO.class);
        Employee employee = dao.findById(1);
        System.out.print(employee);

        session.close();
    }

    /**
     * 测试增加
     * @throws IOException
     */
    @Test
    public  void demo2() throws IOException {
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        SqlSession session = sqlSessionFactory.openSession();

        IEmployeeDAO dao = session.getMapper(IEmployeeDAO.class);
        Employee employee = new Employee();
        employee.setLastName("呵呵");
        employee.setGender("女");
        employee.setEmail("aaa@aaa.com");
        dao.addEmployee(employee);

        session.commit();
        session.close();
    }

    /**
     * 测试修改
     * @throws IOException
     */
    @Test
    public  void demo3() throws IOException {
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        SqlSession session = sqlSessionFactory.openSession();

        IEmployeeDAO dao = session.getMapper(IEmployeeDAO.class);
        Employee employee = new Employee();
        employee.setId(1);
        employee.setLastName("呵呵");
        employee.setGender("女");
        employee.setEmail("aaa@aaa.com");
        dao.updateEmployee(employee);

        session.commit();
        session.close();
    }

    /**
     * 测试修改
     * @throws IOException
     */
    @Test
    public  void demo4() throws IOException {
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        SqlSession session = sqlSessionFactory.openSession();

        IEmployeeDAO dao = session.getMapper(IEmployeeDAO.class);
        dao.deleteEmployeeById(1);

        session.commit();
        session.close();
    }

}

2. 主键生成方式

2.1 若数据库支持自动生成主键的字段（比如MySQL和SQLServer），则可以设置unGeneratedKeys="true"，然后再把keyProperty设置到目标属性上。

<insert id="addEmployee" parameterType="cn.demo1.Employee" useGeneratedKeys="true" keyProperty="id">
    insert into employee(last_name,email,gender) values (#{lastName},#{email},#{gender})
</insert>

package cn.demo1;

import org.apache.ibatis.type.Alias;

/**
 * 描述：POJO
 */
@Alias("emp")
public class Employee {
    private Integer id;
    private String lastName;
    private String gender;
    private String email;

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    public String getGender() {
        return gender;
    }

    public void setGender(String gender) {
        this.gender = gender;
    }

    @Override
    public String toString() {
        return "Employee{" +
                "id=" + id +
                ", lastName='" + lastName + '\'' +
                ", gender='" + gender + '\'' +
                ", email='" + email + '\'' +
                '}';
    }
}

package cn.demo1;

public interface IEmployeeDAO {
    public Employee findById(Integer id);

    public void addEmployee(Employee employee);

    public void updateEmployee(Employee employee);

    public void deleteEmployeeById(Integer id);
}

<?xml version="1.0" encoding="UTF-8" ?>
        <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="cn.demo1.IEmployeeDAO">
<!--
    namespace：命名空间  指定为接口的全类名
    id:唯一标识 和接口中的方法名相同
    resultType：返回值类型
-->
<select id="findById" parameterType="int" resultType="emp" databaseId="mysql">
    select id,last_name,email,gender from employee where id = #{id}
</select>

<insert id="addEmployee" parameterType="cn.demo1.Employee"  useGeneratedKeys="true" keyProperty="id">
    insert into employee(last_name,email,gender) values (#{lastName},#{email},#{gender})
</insert>

<update id="updateEmployee" parameterType="cn.demo1.Employee">
    update employee set last_name = #{lastName} ,email = #{email},gender = #{gender} where id = #{id}
</update>

<delete id="deleteEmployeeById" parameterType="java.lang.Integer">
    delete from employee where id = #{id}
</delete>

</mapper>

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>

    <!--
        Mybatis可以使用properties属性来引入外部properties配置文件内容
            resource:引入类路径下的资源
            url:引入网络路径或磁盘路径下的资源
    -->
    <properties resource="db.properties"></properties>

    <settings>
        <!--
            是否开启自动驼峰规则映射，即如果数据表中的字段是last_name到Java中的lastName等类似的映射
         -->
        <setting name="mapUnderscoreToCamelCase" value="true"/>
    </settings>

    <!--
        typeAliases:别名处理器，可以为Java类型起别名
    -->
    <typeAliases>
        <!--
            类很多情况下，可以批量设置别名这个包下的每一个类创建一个默认的别名，就是简单类名小写。
        -->
       <package name="cn.demo1"/>
    </typeAliases>

    <!--
        environments ，Mybatis可以配置多种环境
            environment，配置一个具体的环境信息，必须有两个标签，ID表示当前环境的唯一标识
                transactionManager s事务管理器
                    type 事务管理器的类型
                        JDBC   this.typeAliasRegistry.registerAlias("JDBC", JdbcTransactionFactory.class);
                        MANAGER  this.typeAliasRegistry.registerAlias("MANAGED", ManagedTransactionFactory.class);
                dataSource
                        JNDI    this.typeAliasRegistry.registerAlias("JNDI", JndiDataSourceFactory.class);
                        POOLED  this.typeAliasRegistry.registerAlias("POOLED", PooledDataSourceFactory.class);
                        UNPOOLED  this.typeAliasRegistry.registerAlias("UNPOOLED", UnpooledDataSourceFactory.class);
    -->
    <environments default="mysql_development">
        <environment id="mysql_development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${jdbc.driver}"/>
                <property name="url" value="${jdbc.url}"/>
                <property name="username" value="${jdbc.user}"/>
                <property name="password" value="${jdbc.password}"/>
            </dataSource>
        </environment>
        <environment id="oracle_development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${oracle.driver}"/>
                <property name="url" value="${oracle.url}"/>
                <property name="username" value="${oracle.user}"/>
                <property name="password" value="${oracle.password}"/>
            </dataSource>
        </environment>
    </environments>

    <databaseIdProvider type="DB_VENDOR">
        <property name="MySQL" value="mysql"/>
        <property name="Oracle" value="oracle"/>
        <property name="SQL Server" value="sqlserver"/>
    </databaseIdProvider>

    <mappers>
        <mapper resource="cn/demo1/EmployeeMapper.xml"/>
    </mappers>
</configuration>

 /**
     * 测试增加
     * @throws IOException
     */
    @Test
    public  void demo2() throws IOException {
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        SqlSession session = sqlSessionFactory.openSession();

        IEmployeeDAO dao = session.getMapper(IEmployeeDAO.class);
        Employee employee = new Employee();
        employee.setLastName("呵呵");
        employee.setGender("女");
        employee.setEmail("aaa@aaa.com");
        dao.addEmployee(employee);

        System.out.print(employee.getId());
        session.commit();
        session.close();
    }

2.2 对于不支持自增主键的数据库，则可以使用selectKey子元素；selectKey元素将会首先运行，id会被设置，后插入语句会被调用。

<insert id="addEmployee" parameterType="cn.demo1.Employee"   databaseId="oracle">
    <selectKey order="BEFORE" keyProperty="id" resultType="java.lang.Integer">
        select employee_seq.nextval from dual;
    </selectKey>
    insert into employee(id,last_name,email,gender) values (#{id},#{lastName},#{email},#{gender})
</insert>

3 参数传递

单个参数：
- 可以接受基本类型，对象类型，集合类型的值。这种情况可直接使用这个参数，不需要经过任何处理。
多个参数：
- 任意多个参数，都会被Mybatis重新包装成一个Map传入。Map的key是param1，param2,0,1...值就是参数的值。
命名参数：
- 为参数使用@param起一个名字，Mybatis就会将这些参数封装到map中，key就是我们自己指定的名字。　　
POJO：
- 当这些参数属于业务的POJO的时候，我们直接传递POJO。#{属性值}中的属性值为POJO的属性值。
Map：
- 我们也可以封装多个参数为map，直接传递。　　
注意：
- 如果是Collection类型的话，那么key是collection。
- 如果是List类型的话，那么key是list。
- 如果是数组的话，那么key是array。
#{key}：获取参数的值，预编译到SQL中。安全。${key}：获取参数的值，拼接到SQL中，有SQL注入问题。
#{}：更丰富的用法
- jdbcType：通常需要在某种特定的条件下设置
- 当我们使用的数据为null的时候，有些数据库不能识别mybatis对null的默认处理，比如Oracle。
- mybatis对所有的null默认映射的是OTHER，Oracle不支持。
- 解决方案：
  - #{email，jdbcType=NULL}
  - 在全局配置文件中配置jdbcTypeForNUll=NULL.

4. select元素

select元素来定义查询操作。
id：唯一标识符。
- 用来引用这条语句，需要和接口的方法名一致。
parameterType：参数类型
- 可以不传，Mybatis会根据TypeHandler自动推断。
resultType：返回值类型
- 别名或者全类名，如果返回的是集合，定义集合中元素的类型。不能和resultMap同时使用。

4.1 resultType：返回的是List集合　　　　　　

public List<Employee> findAll();

<select id="findAll" resultType="cn.demo1.Employee">
    select * from employee
</select>

 @Test
    public  void demo1() throws IOException {
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        SqlSession session = sqlSessionFactory.openSession();

        IEmployeeDAO dao = session.getMapper(IEmployeeDAO.class);
        List<Employee> employees = dao.findAll();
        System.out.print(employees);
        session.close();
    }

4.2 resultType：返回的是Map集合---返回的是一条记录

如果返回的是Map集合，那么Map集合的key是列名，而value是key对应的值

 //key就是列名 值是对应的值
    public Map<String,Object> findEmployeeById(Integer id);

<select id="findEmployeeById" resultType="map">
  select * from employee where id = #{id}
</select>

 @Test
    public  void demo1() throws IOException {
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        SqlSession session = sqlSessionFactory.openSession();

        IEmployeeDAO dao = session.getMapper(IEmployeeDAO.class);
        Map<String, Object> employee = dao.findEmployeeById(5);
        System.out.print(employee);
        session.close();
    }

4.3 resultType：返回的是Map集合---返回的是多条记录

 //key是这条记录的主键，value是记录封装后的JavaBean
    @MapKey("id")
    public Map<Integer,Employee> findEmployeeLikeName(String name);

<select id="findEmployeeLikeName" resultType="cn.demo1.Employee">
    select * from Employee where last_name like '%${value}%'
</select>

 @Test
    public  void demo1() throws IOException {
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        SqlSession session = sqlSessionFactory.openSession();

        IEmployeeDAO dao = session.getMapper(IEmployeeDAO.class);

        Map<Integer, Employee> map = dao.findEmployeeLikeName("呵");
        System.out.print(map);
        session.close();
    }

4.4 resultMap--自定义结果映射规则

主要代码：

 public Employee getEmployeeById(Integer id);

    <!--
        自定义某个Javabean的封装规则
            type：自定义规则的Javabean
            id:唯一id方便引用
     -->
    <resultMap id="emp" type="cn.demo1.Employee">
        <!--
            指定主键列的封装规则
            id定义主键
                cloumn 指定那一列
                property：指定对应的Javabean属性
            result定义普通列封装规则
        -->
        <id property="id" column="id"/>
        <result column="last_name" property="lastName"></result>
        <result column="gender" property="gender"></result>
        <result column="email" property="email"></result>
    </resultMap>

    <select id="getEmployeeById" resultMap="emp">

        select * from employee where id = #{id}

    </select>

  * 测试查询
     * @throws IOException
     */
    @Test
    public  void demo1() throws IOException {
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        SqlSession session = sqlSessionFactory.openSession();

        IEmployeeDAO dao = session.getMapper(IEmployeeDAO.class);

        Employee employee = dao.getEmployeeById(5);

        System.out.print(employee);

        session.close();
    }

全部代码：

POJO

package cn.demo1;

import org.apache.ibatis.type.Alias;

/**
 * 描述：POJO
 */
public class Employee {
    private Integer id;
    private String lastName;
    private String gender;
    private String email;

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    public String getGender() {
        return gender;
    }

    public void setGender(String gender) {
        this.gender = gender;
    }

    @Override
    public String toString() {
        return "Employee{" +
                "id=" + id +
                ", lastName='" + lastName + '\'' +
                ", gender='" + gender + '\'' +
                ", email='" + email + '\'' +
                '}';
    }
}

接口

package cn.demo1;

import org.apache.ibatis.annotations.MapKey;

import java.util.List;
import java.util.Map;

public interface IEmployeeDAO {

    public Employee getEmployeeById(Integer id);

}

映射文件

<?xml version="1.0" encoding="UTF-8" ?>
        <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="cn.demo1.IEmployeeDAO">
    <!--
        自定义某个Javabean的封装规则
            type：自定义规则的Javabean
            id:唯一id方便引用
     -->
    <resultMap id="emp" type="cn.demo1.Employee">
        <!--
            指定主键列的封装规则
            id定义主键
                cloumn 指定那一列
                property：指定对应的Javabean属性
            result定义普通列封装规则
        -->
        <id property="id" column="id"/>
        <result column="last_name" property="lastName"></result>
        <result column="gender" property="gender"></result>
        <result column="email" property="email"></result>
    </resultMap>

    <select id="getEmployeeById" resultMap="emp">

        select * from employee where id = #{id}

    </select>

</mapper>

Mybatis的核心配置文件

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>

    <settings>
        <!--
            是否开启自动驼峰规则映射，即如果数据表中的字段是last_name到Java中的lastName等类似的映射
         -->
        <setting name="mapUnderscoreToCamelCase" value="true"/>
    </settings>

    <environments default="mysql_development">
        <environment id="mysql_development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${jdbc.driver}"/>
                <property name="url" value="${jdbc.url}"/>
                <property name="username" value="${jdbc.user}"/>
                <property name="password" value="${jdbc.password}"/>
            </dataSource>
        </environment>
        <environment id="oracle_development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${oracle.driver}"/>
                <property name="url" value="${oracle.url}"/>
                <property name="username" value="${oracle.user}"/>
                <property name="password" value="${oracle.password}"/>
            </dataSource>
        </environment>
    </environments>

    <databaseIdProvider type="DB_VENDOR">
        <property name="MySQL" value="mysql"/>
        <property name="Oracle" value="oracle"/>
        <property name="SQL Server" value="sqlserver"/>
    </databaseIdProvider>

    <mappers>
        <mapper resource="cn/demo1/EmployeeMapper.xml"/>
    </mappers>
</configuration>

测试

package cn.test;

import cn.demo1.Employee;
import cn.demo1.IEmployeeDAO;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Test;
import sun.font.LayoutPathImpl;

import java.io.IOException;
import java.io.InputStream;
import java.util.List;
import java.util.Map;

/**
 *
 * 描述：
 */

public class MybatisTest {
    /**
     * 测试查询
     * @throws IOException
     */
    @Test
    public  void demo1() throws IOException {
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        SqlSession session = sqlSessionFactory.openSession();

        IEmployeeDAO dao = session.getMapper(IEmployeeDAO.class);

        Employee employee = dao.getEmployeeById(5);

        System.out.print(employee);

        session.close();
    }

}

4.5 resultMap--关联查询--级联属性封装结果集

SQL：

CREATE DATABASE mybatis;
USER DATABASE mybatis;
CREATE TABLE employee(
    id ) PRIMARY KEY AUTO_INCREMENT,
    last_name ),
    gender ),
    email )
);
CREATE TABLE department(
    id ) PRIMARY KEY AUTO_INCREMENT,
    department_name )
)
);
ALTER TABLE employee ADD CONSTRAINT fk_emp_dept FOREIGN KEY (dept_id) REFERENCES department(id);

POJO

package cn.demo1;

public class Department {
    private Integer id;
    private String departmentName;

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getDepartmentName() {
        return departmentName;
    }

    public void setDepartmentName(String departmentName) {
        this.departmentName = departmentName;
    }

    @Override
    public String toString() {
        return "Department{" +
                "id=" + id +
                ", departmentName='" + departmentName + '\'' +
                '}';
    }
}

package cn.demo1;

import org.apache.ibatis.type.Alias;

/**
 * 描述：POJO
 */
public class Employee {
    private Integer id;
    private String lastName;
    private String gender;
    private String email;
    private Department department;

    public Department getDepartment() {
        return department;
    }

    public void setDepartment(Department department) {
        this.department = department;
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    public String getGender() {
        return gender;
    }

    public void setGender(String gender) {
        this.gender = gender;

    }

    @Override
    public String toString() {
        return "Employee{" +
                "email='" + email + '\'' +
                ", gender='" + gender + '\'' +
                ", lastName='" + lastName + '\'' +
                ", id=" + id +
                '}';
    }
}

映射文件 -- EmployeeMapper.xml

<?xml version="1.0" encoding="UTF-8" ?>
        <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="cn.demo1.IEmployeeDAO">

    <resultMap id="mybatis" type="cn.demo1.Employee">
        <id property="id" column="id"/>
        <result property="lastName" column="last_name"/>
        <result property="email" column="email"/>
        <result property="gender" column="gender"/>
        <result property="department.id" column="dept_id"/>
        <result property="department.departmentName" column="department_name"/>

    </resultMap>

    <select id="getEmployeeAndDepartmentById" resultMap="mybatis">
      SELECT e.id id,e.last_name last_name ,e.email email,e.gender gender,e.dept_id dept_id ,d.department_name department_name FROM employee e , department d WHERE e.dept_id = d.id AND e.id = #{id} ;
    </select>

</mapper>

接口--IEmployeeDAO

package cn.demo1;

import org.apache.ibatis.annotations.MapKey;

import java.util.List;
import java.util.Map;

public interface IEmployeeDAO {

    public Employee getEmployeeAndDepartmentById(Integer id);

}

db.properties

jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/mybatis?characterEncoding=utf8
jdbc.user=root
jdbc.password=root

Mybatis核心配置文件

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>

    <!--
    <settings>
        &lt;!&ndash;
            是否开启自动驼峰规则映射，即如果数据表中的字段是last_name到Java中的lastName等类似的映射
         &ndash;&gt;
        <setting name="mapUnderscoreToCamelCase" value="true"/>
    </settings>-->

    <properties resource="db.properties"/>

    <environments default="mysql_development">
        <environment id="mysql_development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${jdbc.driver}"/>
                <property name="url" value="${jdbc.url}"/>
                <property name="username" value="${jdbc.user}"/>
                <property name="password" value="${jdbc.password}"/>
            </dataSource>
        </environment>
        <!--<environment id="oracle_development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${oracle.driver}"/>
                <property name="url" value="${oracle.url}"/>
                <property name="username" value="${oracle.user}"/>
                <property name="password" value="${oracle.password}"/>
            </dataSource>
        </environment>-->
    </environments>

    <databaseIdProvider type="DB_VENDOR">
        <property name="MySQL" value="mysql"/>
        <property name="Oracle" value="oracle"/>
        <property name="SQL Server" value="sqlserver"/>
    </databaseIdProvider>

    <mappers>
        <mapper resource="cn/demo1/EmployeeMapper.xml"/>
    </mappers>
</configuration>

测试

package cn.test;

import cn.demo1.Employee;
import cn.demo1.IEmployeeDAO;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Test;

import java.io.IOException;
import java.io.InputStream;

/**
 *
 * 描述：
 */

public class MybatisTest {
    /**
     * 测试查询
     * @throws IOException
     */
    @Test
    public  void demo1() throws IOException {
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        SqlSession session = sqlSessionFactory.openSession();

        IEmployeeDAO dao = session.getMapper(IEmployeeDAO.class);

        Employee employee = dao.getEmployeeAndDepartmentById(6);
        System.out.print(employee);
        System.out.print(employee.getDepartment());

        session.close();
    }

}

4.6 resultMap--关联查询--association定义关联对象的封装规则

    <resultMap id="mybatis2" type="cn.demo1.Employee">
        <id property="id" column="id"/>
        <result property="lastName" column="last_name"/>
        <result property="email" column="email"/>
        <result property="gender" column="gender"/>
        <!--
            association可以指定联合的JavaBean对象
                property:指定那个属性是联合对象
                javaType:指定这个属性对象的类型
        -->
        <association property="department" javaType="cn.demo1.Department">
            <id column="dept_id" property="id"/>
            <result column="department_name" property="departmentName"/>
        </association>

    </resultMap>

4.6 resultMap--关联查询--association进行分布查询

POJO

package cn.demo1;

public class Department {
    private Integer id;
    private String departmentName;

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getDepartmentName() {
        return departmentName;
    }

    public void setDepartmentName(String departmentName) {
        this.departmentName = departmentName;
    }

    @Override
    public String toString() {
        return "Department{" +
                "id=" + id +
                ", departmentName='" + departmentName + '\'' +
                '}';
    }
}

package cn.demo1;

import org.apache.ibatis.type.Alias;

/**
 * 描述：POJO
 */
public class Employee {
    private Integer id;
    private String lastName;
    private String gender;
    private String email;
    private Department department;

    public Department getDepartment() {
        return department;
    }

    public void setDepartment(Department department) {
        this.department = department;
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    public String getGender() {
        return gender;
    }

    public void setGender(String gender) {
        this.gender = gender;

    }

    @Override
    public String toString() {
        return "Employee{" +
                "email='" + email + '\'' +
                ", gender='" + gender + '\'' +
                ", lastName='" + lastName + '\'' +
                ", id=" + id +
                '}';
    }
}

接口

package cn.demo1;

public interface IDepartmentDAO {

    public Department getDepartmentById(Integer id);

}

package cn.demo1;

import org.apache.ibatis.annotations.MapKey;

import java.util.List;
import java.util.Map;

public interface IEmployeeDAO {

    public Employee getEmployeeByStep(Integer id);

}

映射文件--DepartmentMapper.xml和EmployeeMapper.xml

<?xml version="1.0" encoding="UTF-8" ?>
        <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="cn.demo1.IDepartmentDAO">

    <resultMap id="department" type="cn.demo1.Department">
        <id column="id" property="id"></id>
        <result column="department_name" property="departmentName"/>
    </resultMap>

    <select id="getDepartmentById" resultMap="department">
        select id ,department_name from department where id = #{id}
    </select>

</mapper>

<?xml version="1.0" encoding="UTF-8" ?>
        <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="cn.demo1.IEmployeeDAO">

    <!--
        使用association进行分布查询
            先按照员工Id查询员工信息
            根据员工信息中的dept_id的值去部门表查询部门信息
            将部门设置到员工中
    -->

    <resultMap id="emp" type="cn.demo1.Employee">
        <id property="id" column="id"/>
        <result property="lastName" column="last_name"/>
        <result property="email" column="email"/>
        <result property="gender" column="gender"/>

        <!--
            定义关联对象的封装规则
        -->
        <association property="department" select="cn.demo1.IDepartmentDAO.getDepartmentById" column="dept_id">

        </association>

    </resultMap>

    <select id="getEmployeeByStep" resultMap="emp">
        select id,last_name,email,gender,dept_id from employee where id = #{id}

    </select>

</mapper>

db.properties

jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/mybatis?characterEncoding=utf8
jdbc.user=root
jdbc.password=root

核心配置文件

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>

    <!--
    <settings>
        &lt;!&ndash;
            是否开启自动驼峰规则映射，即如果数据表中的字段是last_name到Java中的lastName等类似的映射
         &ndash;&gt;
        <setting name="mapUnderscoreToCamelCase" value="true"/>
    </settings>-->

    <properties resource="db.properties"/>

    <environments default="mysql_development">
        <environment id="mysql_development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${jdbc.driver}"/>
                <property name="url" value="${jdbc.url}"/>
                <property name="username" value="${jdbc.user}"/>
                <property name="password" value="${jdbc.password}"/>
            </dataSource>
        </environment>
        <!--<environment id="oracle_development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${oracle.driver}"/>
                <property name="url" value="${oracle.url}"/>
                <property name="username" value="${oracle.user}"/>
                <property name="password" value="${oracle.password}"/>
            </dataSource>
        </environment>-->
    </environments>

    <databaseIdProvider type="DB_VENDOR">
        <property name="MySQL" value="mysql"/>
        <property name="Oracle" value="oracle"/>
        <property name="SQL Server" value="sqlserver"/>
    </databaseIdProvider>

    <mappers>
        <mapper resource="cn/demo1/EmployeeMapper.xml"/>
        <mapper resource="cn/demo1/DepartmentMapper.xml"/>
    </mappers>
</configuration>

测试类

package cn.test;

import cn.demo1.Employee;
import cn.demo1.IEmployeeDAO;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Test;

import java.io.IOException;
import java.io.InputStream;

/**
 *
 * 描述：
 */

public class MybatisTest {
    /**
     * 测试查询
     * @throws IOException
     */
    @Test
    public  void demo1() throws IOException {
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        SqlSession session = sqlSessionFactory.openSession();

        IEmployeeDAO dao = session.getMapper(IEmployeeDAO.class);

        Employee employee = dao.getEmployeeByStep(6);
        System.out.print(employee);
        System.out.print(employee.getDepartment());

        session.close();
    }

}

4.6 resultMap--关联查询--association进行分布查询及延迟加载

开启延迟加载和属性按需加载

<settings>
        <setting name="lazyLoadingEnabled" value="true"/>
        <setting name="aggressiveLazyLoading" value="false"/>
    </settings>

4.7 resultMap--关联查询--collection定义关联集合封装规则

POJO

package cn.demo1;

import java.util.List;

public class Department {
    private Integer id;
    private String departmentName;
    private List<Employee> emps;

    public List<Employee> getEmps() {
        return emps;
    }

    public void setEmps(List<Employee> emps) {
        this.emps = emps;
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getDepartmentName() {
        return departmentName;
    }

    public void setDepartmentName(String departmentName) {
        this.departmentName = departmentName;
    }

    @Override
    public String toString() {
        return "Department{" +
                "id=" + id +
                ", departmentName='" + departmentName + '\'' +
                '}';
    }
}

package cn.demo1;

import org.apache.ibatis.type.Alias;

/**
 * 描述：POJO
 */
public class Employee {
    private Integer id;
    private String lastName;
    private String gender;
    private String email;
    private Department department;

    public Department getDepartment() {
        return department;
    }

    public void setDepartment(Department department) {
        this.department = department;
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    public String getGender() {
        return gender;
    }

    public void setGender(String gender) {
        this.gender = gender;

    }

    @Override
    public String toString() {
        return "Employee{" +
                "email='" + email + '\'' +
                ", gender='" + gender + '\'' +
                ", lastName='" + lastName + '\'' +
                ", id=" + id +
                '}';
    }
}

接口

package cn.demo1;

public interface IDepartmentDAO {

    public Department getDepartmentAndEmployeeById(Integer id);
}

映射文件

<?xml version="1.0" encoding="UTF-8" ?>
        <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="cn.demo1.IDepartmentDAO">

    <resultMap id="department" type="cn.demo1.Department">
        <id column="id" property="id"></id>
        <result column="department_name" property="departmentName"/>
        <!--
            collection定义关联集合类型的属性的封装规则
            ofType：指定集合里面元素的类型
        -->
        <collection property="emps" ofType="cn.demo1.Employee">
            <id column="eid" property="id"/>
            <result column="last_name" property="lastName"/>
            <result column="email" property="email"/>
            <result column="gender" property="gender"/>
        </collection>
    </resultMap>

    <select id="getDepartmentAndEmployeeById" resultMap="department">
        SELECT e.id eid,e.last_name last_name ,e.email email,e.gender gender,d.id id ,d.department_name department_name FROM employee e , department d WHERE e.dept_id = d.id AND d.id = #{id}
    </select>

</mapper>

核心配置文件

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>

    <properties resource="db.properties"/>

    <settings>
        <setting name="lazyLoadingEnabled" value="true"/>
        <setting name="aggressiveLazyLoading" value="false"/>
    </settings>

    <environments default="mysql_development">
        <environment id="mysql_development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${jdbc.driver}"/>
                <property name="url" value="${jdbc.url}"/>
                <property name="username" value="${jdbc.user}"/>
                <property name="password" value="${jdbc.password}"/>
            </dataSource>
        </environment>
        <!--<environment id="oracle_development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${oracle.driver}"/>
                <property name="url" value="${oracle.url}"/>
                <property name="username" value="${oracle.user}"/>
                <property name="password" value="${oracle.password}"/>
            </dataSource>
        </environment>-->
    </environments>

    <databaseIdProvider type="DB_VENDOR">
        <property name="MySQL" value="mysql"/>
        <property name="Oracle" value="oracle"/>
        <property name="SQL Server" value="sqlserver"/>
    </databaseIdProvider>

    <mappers>
        <mapper resource="cn/demo1/EmployeeMapper.xml"/>
        <mapper resource="cn/demo1/DepartmentMapper.xml"/>
    </mappers>
</configuration>

测试

package cn.test;

import cn.demo1.Department;
import cn.demo1.Employee;
import cn.demo1.IDepartmentDAO;
import cn.demo1.IEmployeeDAO;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Test;

import java.io.IOException;
import java.io.InputStream;

/**
 *
 * 描述：
 */

public class MybatisTest {
    /**
     * 测试查询
     * @throws IOException
     */
    @Test
    public  void demo1() throws IOException {
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        SqlSession session = sqlSessionFactory.openSession();

        IDepartmentDAO dao = session.getMapper(IDepartmentDAO.class);
        Department department = dao.getDepartmentAndEmployeeById(1);
        System.out.print(department);
        System.out.print(department.getEmps());

        session.close();
    }

}

4.7 resultMap--关联查询--collection进行分布查询

POJO

package cn.demo1;

import java.util.List;

public class Department {
    private Integer id;
    private String departmentName;
    private List<Employee> emps;

    public List<Employee> getEmps() {
        return emps;
    }

    public void setEmps(List<Employee> emps) {
        this.emps = emps;
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getDepartmentName() {
        return departmentName;
    }

    public void setDepartmentName(String departmentName) {
        this.departmentName = departmentName;
    }

    @Override
    public String toString() {
        return "Department{" +
                "id=" + id +
                ", departmentName='" + departmentName + '\'' +
                '}';
    }
}

package cn.demo1;

import org.apache.ibatis.type.Alias;

/**
 * 描述：POJO
 */
public class Employee {
    private Integer id;
    private String lastName;
    private String gender;
    private String email;
    private Department department;

    public Department getDepartment() {
        return department;
    }

    public void setDepartment(Department department) {
        this.department = department;
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    public String getGender() {
        return gender;
    }

    public void setGender(String gender) {
        this.gender = gender;

    }

    @Override
    public String toString() {
        return "Employee{" +
                "email='" + email + '\'' +
                ", gender='" + gender + '\'' +
                ", lastName='" + lastName + '\'' +
                ", id=" + id +
                '}';
    }
}

接口

package cn.demo1;

public interface IDepartmentDAO {

    public Department getDepartmentByIdStep(Integer id);
}

package cn.demo1;

import org.apache.ibatis.annotations.MapKey;

import java.util.List;
import java.util.Map;

public interface IEmployeeDAO {

   public List<Employee> getEmployeesByDeptId(Integer id);

}

映射文件

<?xml version="1.0" encoding="UTF-8" ?>
        <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="cn.demo1.IEmployeeDAO">

    <resultMap id="emp" type="cn.demo1.Employee">
        <id property="id" column="id"/>
        <result property="lastName" column="last_name"/>
        <result property="email" column="email"/>
        <result property="gender" column="gender"/>

    </resultMap>

   <select id="getEmployeesByDeptId" resultMap="emp">
       select * from employee where dept_id = #{id}

   </select>

</mapper>

<?xml version="1.0" encoding="UTF-8" ?>
        <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="cn.demo1.IDepartmentDAO">

    <resultMap id="department" type="cn.demo1.Department">
        <id column="id" property="id"></id>
        <result column="department_name" property="departmentName"/>
    <collection property="emps" select="cn.demo1.IEmployeeDAO.getEmployeesByDeptId" column="id"/>
</resultMap>

    <select id="getDepartmentByIdStep" resultMap="department" >
        select id,department_name from department where id = #{id}
    </select>

</mapper>

核心配置文件

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>

    <properties resource="db.properties"/>

    <settings>
        <setting name="lazyLoadingEnabled" value="true"/>
        <setting name="aggressiveLazyLoading" value="false"/>
    </settings>

    <environments default="mysql_development">
        <environment id="mysql_development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${jdbc.driver}"/>
                <property name="url" value="${jdbc.url}"/>
                <property name="username" value="${jdbc.user}"/>
                <property name="password" value="${jdbc.password}"/>
            </dataSource>
        </environment>
        <!--<environment id="oracle_development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${oracle.driver}"/>
                <property name="url" value="${oracle.url}"/>
                <property name="username" value="${oracle.user}"/>
                <property name="password" value="${oracle.password}"/>
            </dataSource>
        </environment>-->
    </environments>

    <databaseIdProvider type="DB_VENDOR">
        <property name="MySQL" value="mysql"/>
        <property name="Oracle" value="oracle"/>
        <property name="SQL Server" value="sqlserver"/>
    </databaseIdProvider>

    <mappers>
        <mapper resource="cn/demo1/EmployeeMapper.xml"/>
        <mapper resource="cn/demo1/DepartmentMapper.xml"/>
    </mappers>
</configuration>

测试

package cn.test;

import cn.demo1.Department;
import cn.demo1.Employee;
import cn.demo1.IDepartmentDAO;
import cn.demo1.IEmployeeDAO;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Test;

import java.io.IOException;
import java.io.InputStream;

/**
 *
 * 描述：
 */

public class MybatisTest {
    /**
     * 测试查询
     * @throws IOException
     */
    @Test
    public  void demo1() throws IOException {
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        SqlSession session = sqlSessionFactory.openSession();

        IDepartmentDAO dao = session.getMapper(IDepartmentDAO.class);
        Department department = dao.getDepartmentByIdStep(1);
        System.out.print(department);
        System.out.print(department.getEmps());

        session.close();
    }

}

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