12.动态SQL

作用：解决大量拼装SQL的工作

1.动态sql
	1)<sql>
		a)把公共的字段抽取出来
		b)用<include refid="base_user">
	2)<if>
		a)条件查询
		b)修改的时候
	3)<where>
		a)自动添加where关键字，去掉多余的and
	4)<trim>
		a)可以代替where和set
	5)<set>
		a)自动添加set关键字，去掉多余的逗号(传多个逗号，只会去掉一个)
	6)<choose>
		a)when
		b)otherwise
	7)<foreach>
		1)collection
			a)如何是数组就写array
			b)如何是集合就写list
			a)如何是Map就写map中的key
		2)open:循环之前添加
		3)close:循环之后添加
		4)separator:分隔符
		5)item:临时变量

　　事例：

0.数据库

1.创建项目

2.建包建配置文件

   com.qf.entity

   com.qf.dao

   com.qf.mapper

   com.qf.utils

mybatis-config.xml  

3.con.qf.entity包中创建实体类

package com.qf.entity;

public class User {

	private Integer id;
	
	private String name;
	
	private String password;
	
	private String isAdmin;

	public User(String name, String password) {
		this.name = name;
		this.password = password;
	}
	public User() {
	}

	public String getPassword() {
		return password;
	}

	public void setPassword(String password) {
		this.password = password;
	}

	public String getName() {
		return name;
	}

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

	public Integer getId() {
		return id;
	}

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

	public String getIsAdmin() {
		return isAdmin;
	}

	public void setIsAdmin(String isAdmin) {
		this.isAdmin = isAdmin;
	}

	@Override
	public String toString() {
		return "User [id=" + id + ", name=" + name + ", password=" + password + ", isAdmin=" + isAdmin + "]";
	}
	
}

　　

4.con.qf.dao包中创建接口

package com.qf.dao;

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

import com.qf.entity.User;

public interface IUserDao {

	public User getUserById(Integer id);
	
	public List<User> findUser(User user);
	
	public List<User> findUser2(User user);
	
	public List<User> findUser3(User user);
	
	public List<User> findUser4(User user);
	
	public List<User> findUser5(List<Integer> ids);
	
	public List<User> findUser6(int[] ids);
	
	public List<User> findUser7(Map<String, Integer[]> map);
	
	public void update(User user);
	
	public void update2(User user);
	
	public List<User> getUserList();

}

5.配置jdbc.properties配置文件

jdbc.url =jdbc:mysql://localhost:3306/1707_hibernate
jdbc.name=root
jdbc.password=root
jdbc.driver=com.mysql.jdbc.Driver

　　

配置mybatis-config.xml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>

	<!-- 加载属性文件 
		resource:本地资源文件
	-->
	<properties resource="jdbc.properties"></properties>

	<typeAliases>
			<package name="com.qf.entity"/>
	</typeAliases>

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

　　

6.com.qf.mapper包创建接口的映射文件

<?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="com.qf.dao.IUserDao">

	<resultMap type="user" id="userMap">
		<result column="is_admin" property="isAdmin"/>
	</resultMap>

	<!-- 把共用的sql都可以抽取出来 -->
	<sql id="base_user">
		id,
		NAME,
		PASSWORD,
		is_admin
	</sql>

	<select id="getUserById" resultMap="userMap">
			SELECT
				<include refid="base_user"></include>
			FROM
				t_user
			WHERE
				id = #{id}
	</select>
	
	<select id="getUserList" resultMap="userMap">
		SELECT
			<include refid="base_user"></include>
		FROM
			t_user
	</select>
	
	<!-- 测试if标签 -->
	<select id="findUser" resultMap="userMap">
		SELECT
			<include refid="base_user"></include>
		FROM
			t_user
		WHERE 
			1 =1 
			<if test="id != null">
				and ID = #{id} 
			</if>
			<!--字符串判断非空的时候有两种情况 -->
			<!--concat 链接字符串 -->
			<if test="name != null and name != ''">
<!-- 				 and name = #{name} -->
				 and name like concat("%",#{name},"%")
			</if>
	</select>
	
	<!-- 测试where标签 -->
	<select id="findUser2" resultMap="userMap">
		SELECT
			<include refid="base_user"></include>
		FROM
			t_user
			<!-- 
				where标签自动添加where关键字，去掉多余的and关键字
			 -->
		<where>
			<if test="id != null">
				and ID = #{id} 
			</if>
			<if test="name != null and name != ''">
				 and name like concat("%",#{name},"%")
			</if>
		</where>	
	</select>
	
	
	<!-- 测试trim标签 -->
	<select id="findUser3" resultMap="userMap">
		SELECT
			<include refid="base_user"></include>
		FROM
			t_user
		<!-- 添加前缀，去掉多余的内容 -->
		<trim prefix="where" prefixOverrides="and">
			<if test="id != null">
				and ID = #{id} 
			</if>
			<if test="name != null and name != ''">
				 and name like concat("%",#{name},"%")
			</if>
		</trim>
	</select>
	
	
	<!-- 测试set标签
		添加set关键字，去掉多余的逗号
	 -->
	<update id="update" parameterType="user">
		UPDATE t_user
		<set>
			<if test="name != null and name != ''">
				 NAME = #{name},
			</if>
			
			<if test="password != null and password != ''">
				 password = #{password}
			</if>
		</set>
		 where id = #{id}
	</update>
	
	<update id="update2" parameterType="user">
		UPDATE t_user
		<trim prefix="set" suffixOverrides=",">
			<if test="name != null and name != ''">
				 NAME = #{name},
			</if>
			
			<if test="password != null and password != ''">
				 password = #{password}
			</if>
		</trim>
		 where id = #{id}
	</update>
	
	
	<!-- 测试when、otherwise标签 -->
	<select id="findUser4" resultMap="userMap">
		SELECT
			<include refid="base_user"></include>
		FROM
			t_user
		<where>
			<choose>
				<when test="name != null and name != ''">
						name like concat("%",#{name},"%")
				</when>			
				<otherwise>
					name is not null
				</otherwise>
		</choose>
		</where>			
	</select>
	
	<!-- 传递list -->
	<select id="findUser5" resultMap="userMap">
		SELECT
			<include refid="base_user"></include>
		FROM
			t_user
		<where>
			id in 
			<foreach collection="list" open="(" close=")" separator="," item="id">
				#{id}
			</foreach>				
		</where>			
	</select>
	
	<!-- 传递数组 -->
	<select id="findUser6" resultMap="userMap">
		SELECT
			<include refid="base_user"></include>
		FROM
			t_user
		<where>
			id in 
			<foreach collection="array" open="(" close=")" separator="," item="id">
				#{id}
			</foreach>				
		</where>			
	</select>
	
	<!-- 传递Map -->
	<select id="findUser7" resultMap="userMap">
		SELECT
			<include refid="base_user"></include>
		FROM
			t_user
		<where>
			id in 
			<foreach collection="ids" open="(" close=")" separator="," item="id">
				#{id}
			</foreach>				
		</where>			
	</select>
	
</mapper>

　　

7.在mybatis-config.xml里面读取Mapper文件

        <!-- Mapper文件 -->
	<mappers>
		<mapper resource="com/qf/mapper/IUserDao.xml" />
	</mappers>
	

8.com.qf.util工具类

package com.qf.utils;

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

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.xml.sax.InputSource;

public class MyBatisUtil {

	private static SqlSessionFactory sqlSessionFactory;

	public static SqlSessionFactory getSqlSessionFactory() {

		if (sqlSessionFactory == null) {
			initSqlSessionFactory(); // 为空再去参加
		}
		return sqlSessionFactory;
	}

	private static void initSqlSessionFactory() {
		InputStream ips = null;
		try {
			// 1.指定配置文件
			ips = Resources.getResourceAsStream("mybatis-config.xml");

			// 2.赋值操作
			synchronized (MyBatisUtil.class) {
				if (sqlSessionFactory == null) {
					sqlSessionFactory = new SqlSessionFactoryBuilder().build(ips);
				}
			}

		} catch (IOException e) {
			e.printStackTrace();
		} finally {
			if (ips != null) {
				try {
					ips.close();
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
		}
	}
}

　　

9.测试类

package com.qf.dao;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.apache.ibatis.session.SqlSession;
import org.apache.log4j.Logger;
import org.junit.Test;

import com.qf.entity.User;
import com.qf.utils.MyBatisUtil;

public class UserDaoTest {

	private Logger logger = Logger.getLogger(UserDaoTest.class);

	/**
	 * useGeneratedKeys：开启主键回填 keyProperty：回填到那个属性
	 */
	/**
	 * 抽取公共sql，查询当个对象
	 */
	@Test
	public void testGetUserById() {
		SqlSession sqlSession = MyBatisUtil.getSqlSessionFactory().openSession();
		IUserDao userDao = sqlSession.getMapper(IUserDao.class);
		User user = userDao.getUserById(4);
		System.out.println(user);
		sqlSession.commit();
		sqlSession.close();
	}

	/**
	 * 抽取公共sql，查询List
	 */
	@Test
	public void testGetUserList() {
		SqlSession sqlSession = MyBatisUtil.getSqlSessionFactory().openSession();
		IUserDao userDao = sqlSession.getMapper(IUserDao.class);
		List<User> userList = userDao.getUserList();
		for (User user2 : userList) {
			System.out.println(user2);
		}
		sqlSession.commit();
		sqlSession.close();
	}

	/**
	 * 测试if标签 初识if
	 */
	@Test
	public void testFindUser() {
		SqlSession sqlSession = MyBatisUtil.getSqlSessionFactory().openSession();
		IUserDao userDao = sqlSession.getMapper(IUserDao.class);
		User user = new User();
		user.setPassword("123");

		List<User> findUser = userDao.findUser(user);
		for (User user2 : findUser) {
			System.out.println(user2);
		}
		sqlSession.commit();
		sqlSession.close();
	}

	/**
	 * 测试if标签 if+模糊查询
	 */
	@Test
	public void testFindUser1() {
		SqlSession sqlSession = MyBatisUtil.getSqlSessionFactory().openSession();
		IUserDao userDao = sqlSession.getMapper(IUserDao.class);
		User user = new User();
		// 模糊查询
		user.setName("张");

		List<User> findUser = userDao.findUser1(user);
		for (User user2 : findUser) {
			System.out.println(user2);
		}
		sqlSession.commit();
		sqlSession.close();
	}

	/**
	 * 测试where标签 初识where
	 */
	@Test
	public void testFindUser2() {
		SqlSession sqlSession = MyBatisUtil.getSqlSessionFactory().openSession();
		IUserDao userDao = sqlSession.getMapper(IUserDao.class);
		User user = new User();
		user.setPassword("123");

		List<User> findUser = userDao.findUser2(user);
		for (User user2 : findUser) {
			System.out.println(user2);
		}
		sqlSession.commit();
		sqlSession.close();
	}

	/**
	 * 测试trim标签
	 */
	@Test
	public void testFindUser3() {
		SqlSession sqlSession = MyBatisUtil.getSqlSessionFactory().openSession();
		IUserDao userDao = sqlSession.getMapper(IUserDao.class);
		User user = new User();
		user.setPassword("123");

		List<User> findUser = userDao.findUser3(user);
		for (User user2 : findUser) {
			System.out.println(user2);
		}
		sqlSession.commit();
		sqlSession.close();
	}

	/**
	 * 测试update标签
	 */
	@Test
	public void testUpdate() {
		SqlSession sqlSession = MyBatisUtil.getSqlSessionFactory().openSession();
		IUserDao userDao = sqlSession.getMapper(IUserDao.class);
		User user = new User();
		user.setId(3);
		user.setName("李四");
		user.setPassword("435");
		userDao.update(user);
		sqlSession.commit();
		sqlSession.close();
	}

	@Test
	public void testUpdate2() {
		SqlSession sqlSession = MyBatisUtil.getSqlSessionFactory().openSession();

		IUserDao userDao = sqlSession.getMapper(IUserDao.class);

		User user = new User();
		user.setId(3);
		user.setName("李5");

		userDao.update2(user);
		sqlSession.commit();
		sqlSession.close();
	}

	/**
	 * 测试when、otherwise标签
	 */
	@Test
	public void testFindUser4() {
		SqlSession sqlSession = MyBatisUtil.getSqlSessionFactory().openSession();

		IUserDao userDao = sqlSession.getMapper(IUserDao.class);

		User user = new User();
		// user.setName("李");

		List<User> findUser4 = userDao.findUser4(user);
		for (User user2 : findUser4) {
			System.out.println(user2);
		}
		sqlSession.commit();
		sqlSession.close();
	}

	/**
	 * 传递list
	 */
	@Test
	public void testFindUser5() {
		SqlSession sqlSession = MyBatisUtil.getSqlSessionFactory().openSession();

		IUserDao userDao = sqlSession.getMapper(IUserDao.class);

		List<Integer> list = new ArrayList<Integer>();
		list.add(2);
		list.add(3);
		list.add(4);
		list.add(5);
		List<User> findUser4 = userDao.findUser5(list);
		for (User user2 : findUser4) {
			System.out.println(user2);
		}
		sqlSession.commit();
		sqlSession.close();
	}

	/**
	 * 传递数组
	 */
	@Test
	public void testFindUser6() {
		SqlSession sqlSession = MyBatisUtil.getSqlSessionFactory().openSession();

		IUserDao userDao = sqlSession.getMapper(IUserDao.class);

		int[] ids = new int[] { 1, 2, 3, 4, 5 };

		List<User> findUser4 = userDao.findUser6(ids);
		for (User user2 : findUser4) {
			System.out.println(user2);
		}
		sqlSession.commit();
		sqlSession.close();
	}

	/**
	 * 测试map
	 */

	@Test
	public void testFindUser7() {
		SqlSession sqlSession = MyBatisUtil.getSqlSessionFactory().openSession();

		IUserDao userDao = sqlSession.getMapper(IUserDao.class);

		Integer[] ids = new Integer[] { 1, 2, 3, 4, 5 };

		Map<String, Integer[]> map = new HashMap<String, Integer[]>();
		map.put("ids", ids);
		List<User> findUser4 = userDao.findUser7(map);
		for (User user2 : findUser4) {
			System.out.println(user2);
		}
		sqlSession.commit();
		sqlSession.close();
	}

}

　总结：