UserMapper.xml（实体类的Sql配置文件,动态sql(标签),sql片段）：
<?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"> <!-- 配置原生Sql语句 --> <mapper namespace="com.xxx.mybatis.mapper.UserMapper"> <!-- Sql片段 --> <sql id="selector"> select id, username, birthday, sex, address from user </sql> <!-- <if>标签, <where>标签 --> <!-- 根据性别和名字查询用户(多个where条件)。 <where>标签可以自动去掉条件前面多余的and (条件后面多余的and 不能去掉,所以and要写在条件前面) --> <select id="selectUserBySexAndUsername" parameterType="User" resultType="User"> <!-- <include refid="selector"/> --> <!-- 可以通过include标签引入sql片段,避免书写大量重复的sql --> select * from user <where> <if test="sex != null and sex != ''"> <!-- <if>标签。 如果输入参数user对象的sex属性不为null且不为'' --> and sex = #{sex} </if> <if test="username != null and username != ''"> and username = #{username} </if> </where> </select> <!-- <foreach>标签 --> <!-- 根据多个ID查询。 id in (1,2,3) --> <select id="selectUserByIds" resultType="User"> <!-- 可以通过包装类属性设置要遍历的集合(或数组)。 parameterType="QueryVo" --> <include refid="selector"/> <!-- 可以通过include标签引入sql片段,避免书写大量重复的sql --> <where> <!-- id in (1,2,3) --> <!-- collection="ids" 可以遍历包装类的ids属性(List类型或数组类型)。 collection="list" 表示遍历的是集合。 collection="array" 表示遍历的是数组 --> <foreach collection="list" item="id" separator="," open="id in (" close=")"> #{id} </foreach> </where> </select> <!-- <set>标签 --> <!-- 修改 --> <update id="updateCustomerById" parameterType="Customer"> update customer <set> <if test="cust_name != null"> cust_name = #{cust_name}, </if> <if test="cust_linkman != null"> cust_linkman = #{cust_linkman}, </if> <!-- set标签会自动将最后多余的逗号","去除 --> </set> <where> cust_id = #{cust_id} </where> </update>QueryVo.java（包装类,封装sql占位符的输入参数）：
package com.xxx.mybatis.pojo; import java.io.Serializable; import java.util.List; // pojo包装对象 public class QueryVo implements Serializable { private static final long serialVersionUID = 1L; //private User user; // 简单pojo对象作为包装对象的属性 List<Integer> ids; //动态sql;在mapper.xml文件中可以通过foreach标签遍历生成动态sql。 //Integer[] ids; public List<Integer> getIdsList() { return ids; } public void setIdsList(List<Integer> ids) { this.ids = ids; } public User getUser() { return user; } public void setUser(User user) { this.user = user; } }Test.java（测试类）：
package com.xxx.mybatis.junit; import java.io.InputStream; import java.util.ArrayList; import java.util.List; 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 com.xxx.mybatis.mapper.UserMapper; import com.xxx.mybatis.pojo.User; public class Test { //根据性别和名字查询用户 @Test public void testfindUserBySexAndUsername() throws Exception { String resource = "sqlMapConfig.xml"; InputStream in = Resources.getResourceAsStream(resource); SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(in); SqlSession sqlSession = sqlSessionFactory.openSession(); //--------------------------------------------------------------------- UserMapper userMapper = sqlSession.getMapper(UserMapper.class); User user = new User(); user.setSex("1"); //user.setUsername("张小明"); List<User> users = userMapper.selectUserBySexAndUsername(user); for (User user2 : users) { System.out.println(user2); } } //根据多个ID查询 @Test public void testfindUserIDs() throws Exception { String resource = "sqlMapConfig.xml"; InputStream in = Resources.getResourceAsStream(resource); SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(in); SqlSession sqlSession = sqlSessionFactory.openSession(); //--------------------------------------------------------------------- UserMapper userMapper = sqlSession.getMapper(UserMapper.class); //Integer[] ids = new Integer[]{16,24,22}; List<Integer> ids = new ArrayList<Integer>(); ids.add(16); ids.add(22); ids.add(24); List<User> users = userMapper.selectUserByIds(ids); //ids可以是List也可以是数组 /* QueryVo vo = new QueryVo(); //包装类 vo.setIdsList(ids); List<User> users = userMapper.selectUserByIds(vo); */ for (User user : users) { System.out.println(user); } } } UserMapper.java（遵循四个原则的Dao层接口）： package com.xxx.mybatis.mapper; import java.util.List; import com.xxx.mybatis.pojo.QueryVo; import com.xxx.mybatis.pojo.User; //其实就是Dao层接口 public interface UserMapper { //遵循四个原则： //UserMapper.xml中配置的命名空间要与该接口的全类名保持一致(com.xxx.mybatis.mapper.UserMapper) //接口中的方法名 == UserMapper.xml中配置的sql语句的id名 //返回值类型 与 UserMapper.xml文件中配置的返回值类型(resultType)要一致 //方法的输入参数类型 与UserMapper.xml中配置的输入参数的类型(parameterType)要一致 //根据性别和名字查询用户 public List<User> selectUserBySexAndUsername(User user); //根据多个id查询用户信息 //public List<User> selectUserByIds(Integer[] ids); //参数是数组 public List<User> selectUserByIds(List<Integer> ids); //参数是List //public List<User> selectUserByIds(QueryVo vo); //参数是包装类 }