mybatis之DAO层自动实现接口

* 使用mybatis举例，使用DAO接口方式实现
* 不需要针对接口去编写具体的实现类代码，编写映射XML文件，直接拿来使用即可。
* 1、导入jar包：mybatis和mysql-connector
* 2、mybatis配置文件：mybatis-config.xml，加载映射XML文件
* 3、编写JavaBean类，如UserBean
* 4、编写DAO接口和映射XML文件（namespace=DAO接口文件路径、id=接口方法名）

mybatis-config-dao.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>
     <!--从外部配置文件导入jdbc信息-->
     <properties resource="jdbc.properties"></properties>

     <environments default="development">
         <environment id="development">
             <transactionManager type="JDBC"/>
             <dataSource type="POOLED">
                 <property name="driver" value="${driver}"/>
                 <property name="url" value="${url}"/>
                 <property name="username" value="${username}"/>
                 <property name="password" value="${password}"/>
             </dataSource>
         </environment>
     </environments>

     <!--指定映射资源文件-->
     <mappers>
         <mapper resource="dao/DaoMapper.xml"/>

     </mappers>
 </configuration>

DaoMapper.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="dao.UserDao">
     <!--id：名称； parameterType传入参数类型； resultType：返回数据类型-->
     <select id="selectOneUser" parameterType="int" resultType="bean.User">
         select * from user where id = #{id}
     </select>

     <!--批量查询-->
     <select id="selectAllUser" resultMap="userList">
         select * from user
     </select>
     <resultMap type="bean.User" id="userList">
         <result property="id" column="id"/>
         <result property="name" column="name"/>
         <result property="age" column="age"/>
     </resultMap>

     <insert id="insertUser" useGeneratedKeys="true" keyProperty="id">
         insert into user (id, name, age) values (#{id} ,#{name}, #{age})
     </insert>

     <update id="updateUser">
       update user set name=#{name},age=#{age} where id=#{id}
    </update>

     <delete id="deleteUser">
         delete from user where id=#{id}
     </delete>

     <!-- 传入多个参数时，自动转换为map形式 -->
     <insert id="insertByColumns" useGeneratedKeys="true" keyProperty="id">
         insert into user (id, name, age) values (NULL ,#{param1}, #{param2})
     </insert>
     <insert id="insertByZhuJie" useGeneratedKeys="true" keyProperty="id">
         insert into user (id, name, age) values (NULL ,#{name}, #{age})
     </insert>
     <insert id="insertByMap" useGeneratedKeys="true" keyProperty="id">
         insert into user (id, name, age) values (NULL ,#{name}, #{age})
     </insert>

 </mapper>

UserDao.java

 package dao;

 import bean.User;
 import org.apache.ibatis.annotations.Param;

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

 /*
 * 使用mybatis举例，使用DAO接口方式实现
 * 不需要针对UserMapperI接口去编写具体的实现类代码，这个具体的实现类由MyBatis帮我们动态构建出来，我们只需要直接拿来使用即可。
 * */
 public interface UserDao {

     // 根据id查询单一数据
     public User selectOneUser(int id);

     // 查询所有用户
     public List<User> selectAllUser();

     // 插入数据
     public int insertUser(User user);

     // 修改用户
     public int updateUser(User user);

     // 删除用户
     public int deleteUser(User user);

     // 插入数据；多参数三种方式：默认Map、使用Map传参和使用注解别名
     public int insertByColumns(String name, int age);
     public int insertByZhuJie(@Param("name") String name, @Param("age") int age);
     public int insertByMap(Map map);

 }

TestDao.java

 package dao;

 import bean.User;
 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.After;
 import org.junit.Before;
 import org.junit.Ignore;
 import org.junit.Test;

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

 /*
 * 使用mybatis举例，使用DAO接口方式实现
 * 不需要针对接口去编写具体的实现类代码，编写映射XML文件，直接拿来使用即可。
 * 1、导入jar包：mybatis和mysql-connector
 * 2、mybatis配置文件：mybatis-config.xml，加载映射XML文件
 * 3、编写JavaBean类，如UserBean
 * 4、编写DAO接口和映射XML文件（namespace=DAO接口文件路径、id=接口方法名）
 * */
 public class TestDao {
     String resource = "mybatis-config-dao.xml";
     SqlSessionFactory sqlSessionFactory = null;
     SqlSession session = null;

     @Before
     public void before() {
 //        System.out.println("Before");
         try {
             InputStream inputStream = Resources.getResourceAsStream(resource);
 //            创建工厂
             sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
 //            创建session对象
             session = sqlSessionFactory.openSession();

         } catch (IOException e) {
             e.printStackTrace();
         }
     }

     @After
     public void close() {
         session.close();
 //        System.out.println("After");
     }

     @Test
     public void testSelectOneUser() {
 //        接口自动实例化
         UserDao userDao = session.getMapper(UserDao.class);
 //        执行sql
         User user = userDao.selectOneUser(1);
         System.out.println(user);
     }

     //    批量查询
     @Test
     public void testSelectAllUser() {
 //        接口自动实例化
         UserDao userDao = session.getMapper(UserDao.class);
 //        执行sql
         List<User> listUser = userDao.selectAllUser();
         System.out.println("记录个数：" + listUser.size());
         System.out.println(listUser);
     }

     //   插入数据
     @Ignore
     @Test
     public void testInsertUser() {
         UserDao userDao = session.getMapper(UserDao.class);
         User user = new User("AA", "29");
         int n = userDao.insertUser(user);
         session.commit();
         System.out.println("插入数据：" + user);
         System.out.println(n);
     }

     // 修改数据
     @Ignore
     @Test
     public void testUpdateUser() {
         UserDao userDao = session.getMapper(UserDao.class);
         User user = new User(2, "Tom5", "29");
         int n = userDao.updateUser(user);
         session.commit();
         System.out.println("修改数据：" + user);
         System.out.println(n);
     }

     // 修改数据
     @Ignore
     @Test
     public void testDeleteUser() {
         UserDao userDao = session.getMapper(UserDao.class);
         User user = new User(13, "XX", "XX");
         int n = userDao.deleteUser(user);
         session.commit();
         System.out.println("删除数据：" + user);
         System.out.println(n);
     }

     //   多参数插入数据的三种方式
     @Ignore
     @Test
     public void testInsertByColumns() {
         UserDao userDao = session.getMapper(UserDao.class);
         String name = "insertByColumns";
         int age = 33;
 //        int n = userDao.insertByColumns(name, age);
 //        int n = userDao.insertByZhuJie(name, age);

         Map map = new HashMap();
         map.put("name", name);
         map.put("age", age);
         int n = userDao.insertByMap(map);

         session.commit();
         System.out.println("插入数据name：" + name);
         System.out.println(n);
     }

 }

User.java

 package bean;

 /**
  * 数据封装类
  * JavaBean
  */
 public class User {
     private int id;
     private String name;
     private String age;

     public User() {

     }

     public User(String name, String age) {
         this.name = name;
         this.age = age;
     }
     public User(int id, String name, String age) {
         this.id = id;
         this.name = name;
         this.age = age;
     }

     public String getName() {
         return name;
     }

     public void setName(String name) {
         this.name = name;
     }

     public String getAge() {
         return age;
     }

     public void setAge(String age) {
         this.age = age;
     }

     public int getId() {
         return id;
     }

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

     @Override
     public String toString() {
         return "User{id：" + id + "; 姓名：" + name + "; 年龄：" + age + "}";
     }
 }