1. MyBatis映射器

2. MyBatis数据基本操作

　　示例项目结构：

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">

    <modelVersion>4.0.0</modelVersion>

    <groupId>libing</groupId>

    <artifactId>com-helloworld-api</artifactId>

    <packaging>war</packaging>

    <version>0.0.1-SNAPSHOT</version>

    <name>com-helloworld-api Maven Webapp</name>

    <url>http://maven.apache.org</url>

    <properties>

        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>

        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>

        <java.version>1.8</java.version>

    </properties>

    <dependencies>

        <dependency>

            <groupId>mysql</groupId>

            <artifactId>mysql-connector-java</artifactId>

            <version>5.1.43</version>

        </dependency>

        <dependency>

            <groupId>org.mybatis</groupId>

            <artifactId>mybatis</artifactId>

            <version>3.4.5</version>

        </dependency>

        <dependency>

            <groupId>junit</groupId>

            <artifactId>junit</artifactId>

            <version>4.12</version>

            <scope>test</scope>

        </dependency>

        <dependency>

            <groupId>javax.servlet</groupId>

            <artifactId>javax.servlet-api</artifactId>

            <version>4.0.0-b07</version>

            <scope>provided</scope>

        </dependency>

    </dependencies>

    <build>

        <finalName>com-helloworld-api</finalName>

        <plugins>

            <plugin>

                <groupId>org.apache.maven.plugins</groupId>

                <artifactId>maven-compiler-plugin</artifactId>

                <version>3.6.2</version>

                <configuration>

                    <source>1.8</source>

                    <target>1.8</target>

                </configuration>

            </plugin>

        </plugins>

    </build>

</project>

pom.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>

    <environments default="development">

        <environment id="development">

            <transactionManager type="JDBC" />

            <dataSource type="POOLED">

                <property name="driver" value="com.mysql.jdbc.Driver" />

                <property name="url" value="jdbc:mysql://localhost:3306/helloworld?characterEncoding=utf-8" />

                <property name="username" value="root" />

                <property name="password" value="root" />

            </dataSource>

        </environment>

    </environments>

    <mappers>

        <mapper resource="mappers/RoleMapper.xml" />

    </mappers>

</configuration>

mybatis-config.xml

package com.libing.helloworld.model;

public class Role {

    private Integer id;

    private String roleName;

    public Integer getId() {

        return id;

    }

    public void setId(Integer id) {

        this.id = id;

    }

    public String getRoleName() {

        return roleName;

    }

    public void setRoleName(String roleName) {

        this.roleName = roleName;

    }

}

Role.java

<?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="com.libing.helloworld.dao.IRoleDao">

    <resultMap id="baseResultMap" type="com.libing.helloworld.model.Role">

        <id property="id" column="id" />

        <result property="roleName" column="role_name" />

    </resultMap>

    <select id="findAll" resultMap="baseResultMap">

        SELECT

            id,

            role_name

        FROM

            role

        ORDER BY id ASC

    </select>

    <select id="findBySearchText" resultMap="baseResultMap">

        SELECT

            id,

            role_name

        FROM

            role

        WHERE

            role_name LIKE CONCAT(CONCAT('%',#{searchText,jdbcType=VARCHAR}),'%')

        ORDER BY id ASC

    </select>

    <select id="findById" resultMap="baseResultMap">

        SELECT

            id,

            role_name

        FROM

            role

        WHERE id = #{id}

    </select>

    <insert id="insert" useGeneratedKeys="true" keyProperty="id" parameterType="com.libing.helloworld.model.Role">

        INSERT role

        (

            role_name

        )

        VALUES

        (

            #{roleName}

        )

    </insert>

    <update id="update" parameterType="com.libing.helloworld.model.Role">

        UPDATE role

        SET

            role_name=#{roleName}

        WHERE

            id = #{id}

    </update>

    <delete id="deleteById">

        DELETE FROM role

        WHERE

            id = #{id}

    </delete>

    <delete id="deleteByIds" parameterType="java.util.List">

        DELETE FROM role

        WHERE

            id IN

        <foreach collection="list" index="index" item="item" open="(" separator="," close=")">

            #{item}

        </foreach>

    </delete>

</mapper>

RoleMapper.xml

package com.libing.helloworld.test;

import java.io.InputStream;

import java.util.ArrayList;

import java.util.List;

import org.apache.ibatis.session.SqlSession;

import org.apache.ibatis.session.SqlSessionFactory;

import org.apache.ibatis.session.SqlSessionFactoryBuilder;

import org.junit.Assert;

import org.junit.Before;

import org.junit.Test;

import com.libing.helloworld.dao.IRoleDao;

import com.libing.helloworld.model.Role;

public class RoleTest {

    SqlSession sqlSession = null;

    @Before

    public void init() {

        String resource = "mybatis-config.xml";

        InputStream inputStream = RoleTest.class.getClassLoader().getResourceAsStream(resource);

        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

        sqlSession = sqlSessionFactory.openSession();

    }

    @Test

    public void findAll() {

        try {

            IRoleDao roleDao = sqlSession.getMapper(IRoleDao.class);

            List<Role> roles = roleDao.findAll();

            Assert.assertNotNull(roles);

            Assert.assertTrue(roles.size() > 0);

        } catch (Exception e) {

            e.printStackTrace();

        } finally {

            sqlSession.close();

        }

    }

    @Test

    public void findById() {

        try {

            IRoleDao roleDao = sqlSession.getMapper(IRoleDao.class);

            Role role = roleDao.findById(1);

            Assert.assertNotNull(role);

            Assert.assertNotNull(role.getRoleName());

        } catch (Exception e) {

            e.printStackTrace();

        } finally {

            sqlSession.close();

        }

    }

    @Test

    public void insert() {

        try {

            IRoleDao roleDao = sqlSession.getMapper(IRoleDao.class);

            Role role = new Role();

            role.setRoleName("测试");

            int result = roleDao.insert(role);

            // 只插入一条记录

            Assert.assertEquals(1, result);

            // id不为null

            Assert.assertNotNull(role.getId());

        } catch (Exception e) {

            e.printStackTrace();

        } finally {

            sqlSession.rollback();

            sqlSession.close();

        }

    }

    public void Update() {

        try {

            IRoleDao roleDao = sqlSession.getMapper(IRoleDao.class);

            Role role = roleDao.findById(1);

            Assert.assertNotNull(role);

            role.setRoleName("测试");

            int result = roleDao.update(role);

            // 只修改一条记录

            Assert.assertEquals(1, result);

            // 修改后的值

            Assert.assertEquals("测试", roleDao.findById(1).getRoleName());

        } catch (Exception e) {

            e.printStackTrace();

        } finally {

            sqlSession.rollback();

            sqlSession.close();

        }

    }

    @Test

    public void deleteById() {

        try {

            IRoleDao roleDao = sqlSession.getMapper(IRoleDao.class);

            Assert.assertNotNull(roleDao.findById(1));

            // 调用删除方法

            Assert.assertEquals(1, roleDao.deleteById(1));

            // 再次查询，判断是否为null

            Assert.assertNull(roleDao.findById(1));

        } catch (Exception e) {

            e.printStackTrace();

        } finally {

            // 由于sqlSessionFactory.openSession()是不自动提交的，不手动执行sqlSession.commit()不会提交到数据库

            sqlSession.rollback();

            sqlSession.close();

        }

    }

    @Test

    public void deleteByIds() {

        try {

            List<Integer> ids = new ArrayList<Integer>();

            ids.add(1);

            ids.add(2);

            IRoleDao roleDao = sqlSession.getMapper(IRoleDao.class);

            int result = roleDao.deleteByIds(ids);

            Assert.assertTrue(result > 0);

        } catch (Exception e) {

            e.printStackTrace();

        } finally {

            sqlSession.rollback();

            sqlSession.close();

        }

    }

}

RoleTest.java

package com.libing.helloworld.dao;

import java.util.List;

import org.apache.ibatis.annotations.Delete;

import org.apache.ibatis.annotations.Insert;

import org.apache.ibatis.annotations.Options;

import org.apache.ibatis.annotations.Param;

import org.apache.ibatis.annotations.Result;

import org.apache.ibatis.annotations.Results;

import org.apache.ibatis.annotations.Select;

import org.apache.ibatis.annotations.SelectKey;

import org.apache.ibatis.annotations.Update;

import com.libing.helloworld.model.Role;

public interface IRoleDao {

    @Select("SELECT id,role_name FROM role")

    @Results( value = {

        @Result(id = true, property = "id", column = "id"),

        @Result(property="roleName", column="role_name")

    })

    List<Role> findAll();

    @Select("SELECT id,role_name FROM role WHERE role_name LIKE CONCAT(CONCAT('%',#{searchText}),'%')")

    @Results( value = {

        @Result(id = true, property = "id", column = "id"),

        @Result(property="roleName", column="role_name")

    })

    List<Role> findBySearchText(@Param("searchText") String searchText);

    @Select("SELECT id,role_name FROM role WHERE id = #{id}")

    @Results( value = {

        @Result(id = true, property = "id", column = "id"),

        @Result(property="roleName", column="role_name")

    })

    Role findById(Integer id);

    @Insert({

        "INSERT INTO role(id,role_name)",

        " VALUES ",

        "(#{id}, #{roleName})"

    })

    @Options(useGeneratedKeys = true, keyProperty = "id")

    @SelectKey(statement="select last_insert_id()", keyProperty = "id", before = false, resultType = int.class)

    int insert(Role role);

    @Update({

        "UPDATE role SET ",

        "role_name = #{roleName} ",

        "WHERE id = #{id}"

    })

    int update(Role role);

    @Delete("DELETE FROM role WHERE id = #{id}")

    int deleteById(Integer id);

    int deleteByIds(List<Integer> ids);

}

IRoleDao.java

2.1 select

　　基于XML方式：

<resultMap id="baseResultMap" type="com.libing.helloworld.model.Role">

    <id property="id" column="id" />

    <result property="roleName" column="role_name" />

</resultMap>

<select id="findAll" resultMap="baseResultMap">

    SELECT

        id,

        role_name

    FROM

        role

    ORDER BY id ASC

</select>

　　基于注解方式：

@Select("SELECT id,role_name FROM role")

@Results( value = {

    @Result(id = true, property = "id", column = "id"),

    @Result(property="roleName", column="role_name")

})

List<Role> findAll();

　　单元测试：

@Test

public void findAll() {

    try {

        IRoleDao roleDao = sqlSession.getMapper(IRoleDao.class);

        List<Role> roles = roleDao.findAll();

        Assert.assertNotNull(roles);

        Assert.assertTrue(roles.size() > 0);

    } catch (Exception e) {

        e.printStackTrace();

    } finally {

        sqlSession.close();

    }

}

　　XML中大于符号与小于符号转义：

　　> >

　　< <

　　或使用 <![CDATA[ ]]>

<select id="findAll" resultMap="baseResultMap">

    SELECT

        id,

        role_name

    FROM

        role

    WHERE id &gt;= 10

    ORDER BY id ASC

</select>

<select id="findAll" resultMap="baseResultMap">

    SELECT

        id,

        role_name

    FROM

        role

    WHERE id <![CDATA[>=]]> 10

    ORDER BY id ASC

</select>

Role findById(Integer id);

<select id="findById" resultMap="baseResultMap">

    SELECT

        id,

        role_name

    FROM

        role

    WHERE

        id = #{id}

</select>

@Test

public void findById() {

    try {

        IRoleDao roleDao = sqlSession.getMapper(IRoleDao.class);

        Role role = roleDao.findById(1);

        Assert.assertNotNull(role);

        Assert.assertNotNull(role.getRoleName());

    } catch (Exception e) {

        e.printStackTrace();

    } finally {

        sqlSession.close();

    }

}

@Select("SELECT id,role_name FROM role WHERE id = #{id}")

@Results( value = {

    @Result(id = true, property = "id", column = "id"),

    @Result(property="roleName", column="role_name")

})

Role findById(Integer id);

　　传递多个参数：

　　1>. 使用Map传递参数

List<Role> findByMap(Map<String, String> params);

<select id="findByMap" parameterType="map" resultMap="baseResultMap">

    SELECT

        id,

        role_name

    FROM

        role

    WHERE

        id != #{id}

    AND

        role_name = #{roleName}

</select>

@Test

public void findByMap() {

    try {

        Map<String, String> params = new HashMap<String, String>();

        params.put("id", "1");

        params.put("roleName", "管理员");

        IRoleDao roleDao = sqlSession.getMapper(IRoleDao.class);

        List<Role> roles = roleDao.findByMap(params);

        Assert.assertNotNull(roles);

        Assert.assertTrue(roles.size() > 0);

    } catch (Exception e) {

        e.printStackTrace();

    } finally {

        sqlSession.close();

    }

}

　　2>. 使用注解方式传递参数

import org.apache.ibatis.annotations.Param;

List<Role> findByAnnotation(@Param("id") Integer id, @Param("roleName") String roleName);

<select id="findByAnnotation" resultMap="baseResultMap">

    SELECT

    　　id,

    　　role_name

    FROM

    　　role

    WHERE

    　　id != #{id}

    AND

    　　role_name = #{roleName}

</select>

　　3>. 使用JavaBean传递参数

package com.libing.helloworld.params;

public class RoleParam {

    private Integer id;

    private String roleName;

    public Integer getId() {

        return id;

    }

    public void setId(Integer id) {

        this.id = id;

    }

    public String getRoleName() {

        return roleName;

    }

    public void setRoleName(String roleName) {

        this.roleName = roleName;

    }

}

RoleParam.java

List<Role> findByRoleParam(RoleParam params);

<select id="findByRoleParam" parameterType="com.libing.helloworld.params.RoleParam" resultMap="baseResultMap">

    SELECT

        id,

        role_name

    FROM

        role

    WHERE

        id != #{id}

    AND

        role_name = #{roleName}

</select>

　　传递多个参数总结：

　　◊ 使用Map方式：Map扩展和维护困难，在实际应用中废弃这种传递参数方式。

　　◊ 使用@Param注解方式：参数个数<=5时是最佳的传参方式。

　　◊ JavaBean方式：当参数个数大于5个时，建议使用JavaBean方式。

2.2 insert

　　MyBatis在执行Insert语句之后返回一个整数，表示插入的记录数。

int insert(Role role);

<insert id="insert" useGeneratedKeys="true" keyProperty="id" parameterType="com.libing.helloworld.model.Role">

    INSERT role

    (

        role_name

    )

    VALUES

    (

        #{roleName}

    )

</insert>

　　其中，useGeneratedKeys：配置MyBatis使用JDBC的getGeneratedKeys()来获取由数据库内部生成的主键值，keyProperty：指定主键字段。

@Test

public void insert() {

    try {

        IRoleDao roleDao = sqlSession.getMapper(IRoleDao.class);

        Role role = new Role();

        role.setRoleName("测试");

        int result = roleDao.insert(role);

        // 只插入一条记录

        Assert.assertEquals(1, result);

        // id不为null

        Assert.assertNotNull(role.getId());

    } catch (Exception e) {

        e.printStackTrace();

    } finally {

        sqlSession.rollback();

        sqlSession.close();

    }

}

@Insert({

    "INSERT INTO role(id,role_name)",

    " VALUES ",

    "(#{id}, #{roleName})"

})

@Options(useGeneratedKeys = true, keyProperty = "id")

@SelectKey(statement="select last_insert_id()", keyProperty = "id", before = false, resultType = int.class)

int insert(Role role);

2.3 update

　　MyBatis在执行update语句之后返回一个整数，表示更新的记录数。

int update(Role role);

<update id="update" parameterType="com.libing.helloworld.model.Role">

    UPDATE role

    SET

        role_name = #{roleName}

    WHERE

        id = #{id}

</update>

@Test

public void Update() {

    try {

        IRoleDao roleDao = sqlSession.getMapper(IRoleDao.class);

        Role role = roleDao.findById(1);

        Assert.assertNotNull(role);

        role.setRoleName("测试");

        int result = roleDao.update(role);

        // 只修改一条记录

        Assert.assertEquals(1, result);

        // 修改后的值

        Assert.assertEquals("测试", roleDao.findById(1).getRoleName());

    } catch (Exception e) {

        e.printStackTrace();

    } finally {

        sqlSession.rollback();

        sqlSession.close();

    }

}

@Update({

    "UPDATE role SET ",

    "role_name = #{roleName} ",

    "WHERE id = #{id}"

})

int update(Role role);

2.4 delete

　　MyBatis在执行delete语句之后返回一个整数，表示删除的记录数。

int deleteById(Integer id);

<delete id="deleteById">

    DELETE FROM role

    WHERE

        id = #{id}

</delete>

@Test

public void deleteById() {

    try {

        IRoleDao roleDao = sqlSession.getMapper(IRoleDao.class);

        Assert.assertNotNull(roleDao.findById(1));

        // 调用删除方法

        Assert.assertEquals(1, roleDao.deleteById(1));

        // 再次查询，判断是否为null

        Assert.assertNull(roleDao.findById(1));

    } catch (Exception e) {

        e.printStackTrace();

    } finally {

        // 由于sqlSessionFactory.openSession()是不自动提交的，不手动执行sqlSession.commit()不会提交到数据库

        sqlSession.rollback();

        sqlSession.close();

    }

}

@Delete("DELETE FROM role WHERE id = #{id}")

int deleteById(Integer id);

　　删除多条记录：

int deleteByIds(List<Integer> ids);

<delete id="deleteByIds" parameterType="java.util.List">

    DELETE FROM role

    WHERE

        id IN

    <foreach collection="list" index="index" item="item" open="("

        separator="," close=")">

        #{item}

    </foreach>

</delete>

@Test

public void deleteByIds() {

    try {

        List<Integer> ids = new ArrayList<Integer>();

        ids.add(1);

        ids.add(2);

        IRoleDao roleDao = sqlSession.getMapper(IRoleDao.class);

        int result = roleDao.deleteByIds(ids);

        Assert.assertTrue(result > 0);

    } catch (Exception e) {

        e.printStackTrace();

    } finally {

        sqlSession.rollback();

        sqlSession.close();

    }

}

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