MyBatis动态SQL示例

Posted 2020-11-27 KeepGoing

【MyBatis】配置文件示例
【MyBatis】映射文件示例

DAO文件

EmployeeMapperDynamicSQL.java

package com.atguigu.mybatis.dao;

import java.util.List;

import org.apache.ibatis.annotations.Param;

import com.atguigu.mybatis.bean.Employee;

public interface EmployeeMapperDynamicSQL {
	
	public List<Employee> getEmpsTestInnerParameter(Employee employee);
	
	//携带了哪个字段查询条件就带上这个字段的值
	public List<Employee> getEmpsByConditionIf(Employee employee);
	
	public List<Employee> getEmpsByConditionTrim(Employee employee);
	
	public List<Employee> getEmpsByConditionChoose(Employee employee);
	
	public void updateEmp(Employee employee);
	
	//查询员工id\'在给定集合中的
	public List<Employee> getEmpsByConditionForeach(@Param("ids")List<Integer> ids);
	
	public void addEmps(@Param("emps")List<Employee> emps);

}

映射文件

EmployeeMapperDynamicSQL.xml MyBatis动态SQL主要包括if、choose、trim、foreach

<?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.atguigu.mybatis.dao.EmployeeMapperDynamicSQL">
	<!-- 
• if:判断
• choose (when, otherwise):分支选择；带了break的swtich-case
	如果带了id就用id查，如果带了lastName就用lastName查;只会进入其中一个
• trim 字符串截取(where(封装查询条件), set(封装修改条件))
• foreach 遍历集合
	 -->
	 <!-- 查询员工，要求，携带了哪个字段查询条件就带上这个字段的值 -->
	 <!-- public List<Employee> getEmpsByConditionIf(Employee employee); -->
	 <select id="getEmpsByConditionIf" resultType="com.atguigu.mybatis.bean.Employee">
	 	select * from tbl_employee
	 	<!-- where -->
	 	<where>
		 	<!-- test：判断表达式（OGNL）
		 	OGNL参照PPT或者官方文档。
		 	  	 c:if  test
		 	从参数中取值进行判断
		 	
		 	遇见特殊符号应该去写转义字符：
		 	&&：
		 	-->
		 	<if test="id!=null">
		 		id=#{id}
		 	</if>
		 	<if test="lastName!=null &amp;&amp; lastName!=&quot;&quot;">
		 		and last_name like #{lastName}
		 	</if>
		 	<if test="email!=null and email.trim()!=&quot;&quot;">
		 		and email=#{email}
		 	</if> 
		 	<!-- ognl会进行字符串与数字的转换判断  "0"==0 -->
		 	<if test="gender==0 or gender==1">
		 	 	and gender=#{gender}
		 	</if>
	 	</where>
	 </select>
	 
	 <!--public List<Employee> getEmpsByConditionTrim(Employee employee);  -->
	 <select id="getEmpsByConditionTrim" resultType="com.atguigu.mybatis.bean.Employee">
	 	select * from tbl_employee
	 	<!-- 后面多出的and或者or where标签不能解决 
	 	prefix="":前缀：trim标签体中是整个字符串拼串 后的结果。
	 			prefix给拼串后的整个字符串加一个前缀 
	 	prefixOverrides="":
	 			前缀覆盖： 去掉整个字符串前面多余的字符
	 	suffix="":后缀
	 			suffix给拼串后的整个字符串加一个后缀 
	 	suffixOverrides=""
	 			后缀覆盖：去掉整个字符串后面多余的字符
	 			
	 	-->
	 	<!-- 自定义字符串的截取规则 -->
	 	<trim prefix="where" suffixOverrides="and">
	 		<if test="id!=null">
		 		id=#{id} and
		 	</if>
		 	<if test="lastName!=null &amp;&amp; lastName!=&quot;&quot;">
		 		last_name like #{lastName} and
		 	</if>
		 	<if test="email!=null and email.trim()!=&quot;&quot;">
		 		email=#{email} and
		 	</if> 
		 	<!-- ognl会进行字符串与数字的转换判断  "0"==0 -->
		 	<if test="gender==0 or gender==1">
		 	 	gender=#{gender}
		 	</if>
		 </trim>
	 </select>
	 
	 <!-- public List<Employee> getEmpsByConditionChoose(Employee employee); -->
	 <select id="getEmpsByConditionChoose" resultType="com.atguigu.mybatis.bean.Employee">
	 	select * from tbl_employee 
	 	<where>
	 		<!-- 如果带了id就用id查，如果带了lastName就用lastName查;只会进入其中一个 -->
	 		<choose>
	 			<when test="id!=null">
	 				id=#{id}
	 			</when>
	 			<when test="lastName!=null">
	 				last_name like #{lastName}
	 			</when>
	 			<when test="email!=null">
	 				email = #{email}
	 			</when>
	 			<otherwise>
	 				gender = 0
	 			</otherwise>
	 		</choose>
	 	</where>
	 </select>
	 
	 <!--public void updateEmp(Employee employee);  -->
	 <update id="updateEmp">
	 	<!-- Set标签的使用 -->
	 	update tbl_employee 
		<set>
			<if test="lastName!=null">
				last_name=#{lastName},
			</if>
			<if test="email!=null">
				email=#{email},
			</if>
			<if test="gender!=null">
				gender=#{gender}
			</if>
		</set>
		where id=#{id} 
<!-- 		
		Trim：更新拼串
		update tbl_employee 
		<trim prefix="set" suffixOverrides=",">
			<if test="lastName!=null">
				last_name=#{lastName},
			</if>
			<if test="email!=null">
				email=#{email},
			</if>
			<if test="gender!=null">
				gender=#{gender}
			</if>
		</trim>
		where id=#{id}  -->
	 </update>
	 
	 <!--public List<Employee> getEmpsByConditionForeach(List<Integer> ids);  -->
	 <select id="getEmpsByConditionForeach" resultType="com.atguigu.mybatis.bean.Employee">
	 	select * from tbl_employee
	 	<!--
	 		collection：指定要遍历的集合：
	 			list类型的参数会特殊处理封装在map中，map的key就叫list
	 		item：将当前遍历出的元素赋值给指定的变量
	 		separator:每个元素之间的分隔符
	 		open：遍历出所有结果拼接一个开始的字符
	 		close:遍历出所有结果拼接一个结束的字符
	 		index:索引。遍历list的时候是index就是索引，item就是当前值
	 				      遍历map的时候index表示的就是map的key，item就是map的值
	 		
	 		#{变量名}就能取出变量的值也就是当前遍历出的元素
	 	  -->
	 	<foreach collection="ids" item="item_id" separator=","
	 		open="where id in(" close=")">
	 		#{item_id}
	 	</foreach>
	 </select>
	 
	 <!-- 批量保存 -->
	 <!--public void addEmps(@Param("emps")List<Employee> emps);  -->
	 <!--mysql下批量保存：可以foreach遍历   mysql支持values(),(),()语法-->
	<insert id="addEmps">
	 	insert into tbl_employee(
	 		<include refid="insertColumn"></include>
	 	) 
		values
		<foreach collection="emps" item="emp" separator=",">
			(#{emp.lastName},#{emp.email},#{emp.gender},#{emp.dept.id})
		</foreach>
	 </insert><!--   -->
	 
	 <!-- 这种方式需要数据库连接属性allowMultiQueries=true；
	 	这种分号分隔多个sql可以用于其他的批量操作（删除，修改） -->
	 <!-- <insert id="addEmps">
	 	<foreach collection="emps" item="emp" separator=";">
	 		insert into tbl_employee(last_name,email,gender,d_id)
	 		values(#{emp.lastName},#{emp.email},#{emp.gender},#{emp.dept.id})
	 	</foreach>
	 </insert> -->
	 
	 <!-- Oracle数据库批量保存： 
	 	Oracle不支持values(),(),()
	 	Oracle支持的批量方式
	 	1、多个insert放在begin - end里面
	 		begin
			    insert into employees(employee_id,last_name,email) 
			    values(employees_seq.nextval,\'test_001\',\'[e-mail]\');
			    insert into employees(employee_id,last_name,email) 
			    values(employees_seq.nextval,\'test_002\',\'[e-mail]\');
			end;
		2、利用中间表：
			insert into employees(employee_id,last_name,email)
		       select employees_seq.nextval,lastName,email from(
		              select \'test_a_01\' lastName,\'test_a_e01\' email from dual
		              union
		              select \'test_a_02\' lastName,\'test_a_e02\' email from dual
		              union
		              select \'test_a_03\' lastName,\'test_a_e03\' email from dual
		       )	
	 -->
	 <insert id="addEmps" databaseId="oracle">
	 	<!-- oracle第一种批量方式 -->
	 	<!-- <foreach collection="emps" item="emp" open="begin" close="end;">
	 		insert into employees(employee_id,last_name,email) 
			    values(employees_seq.nextval,#{emp.lastName},#{emp.email});
	 	</foreach> -->
	 	
	 	<!-- oracle第二种批量方式  -->
	 	insert into employees(
	 		<!-- 引用外部定义的sql -->
	 		<include refid="insertColumn">
	 			<property name="testColomn" value="abc"/>
	 		</include>
	 	)
	 			<foreach collection="emps" item="emp" separator="union"
	 				open="select employees_seq.nextval,lastName,email from("
	 				close=")">
	 				select #{emp.lastName} lastName,#{emp.email} email from dual
	 			</foreach>
	 </insert>
	 
	 <!-- 两个内置参数：
	 	不只是方法传递过来的参数可以被用来判断，取值。。。
	 	mybatis默认还有两个内置参数：
	 	_parameter:代表整个参数
	 		单个参数：_parameter就是这个参数
	 		多个参数：参数会被封装为一个map；_parameter就是代表这个map
	 	
	 	_databaseId:如果配置了databaseIdProvider标签。
	 		_databaseId就是代表当前数据库的别名oracle
	  -->
	  
	  <!--public List<Employee> getEmpsTestInnerParameter(Employee employee);  -->
	  <select id="getEmpsTestInnerParameter" resultType="com.atguigu.mybatis.bean.Employee">
	  		<!-- bind：可以将OGNL表达式的值绑定到一个变量中，方便后来引用这个变量的值 -->
	  		<bind name="_lastName" value="\'%\'+lastName+\'%\'"/>
	  		<if test="_databaseId==\'mysql\'">
	  			select * from tbl_employee
	  			<if test="_parameter!=null">
	  				where last_name like #{lastName}
	  			</if>
	  		</if>
	  		<if test="_databaseId==\'oracle\'">
	  			select * from employees
	  			<if test="_parameter!=null">
	  				where last_name like #{_parameter.lastName}
	  			</if>
	  		</if>
	  </select>
	  
	  <!-- 
	  	抽取可重用的sql片段。方便后面引用 
	  	1、sql抽取：经常将要查询的列名，或者插入用的列名抽取出来方便引用
	  	2、include来引用已经抽取的sql：
	  	3、include还可以自定义一些property，sql标签内部就能使用自定义的属性
	  			include-property：取值的正确方式${prop},
	  			#{不能使用这种方式}
	  -->
	  <sql id="insertColumn">
	  		<if test="_databaseId==\'oracle\'">
	  			employee_id,last_name,email
	  		</if>
	  		<if test="_databaseId==\'mysql\'">
	  			last_name,email,gender,d_id
	  		</if>
	  </sql>
	  
</mapper>

Bean

参见下面中的Bean小节

【MyBatis】映射文件示例

测试类

MyBatisTest.java

package com.atguigu.mybatis.test;

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

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.atguigu.mybatis.bean.Department;
import com.atguigu.mybatis.bean.Employee;
import com.atguigu.mybatis.dao.DepartmentMapper;
import com.atguigu.mybatis.dao.EmployeeMapper;
import com.atguigu.mybatis.dao.EmployeeMapperAnnotation;
import com.atguigu.mybatis.dao.EmployeeMapperDynamicSQL;
import com.atguigu.mybatis.dao.EmployeeMapperPlus;

/**
 * 1、接口式编程
 * 	原生：		Dao		====>  DaoImpl
 * 	mybatis：	Mapper	====>  xxMapper.xml
 * 
 * 2、SqlSession代表和数据库的一次会话；用完必须关闭；
 * 3、SqlSession和connection一样她都是非线程安全。每次使用都应该去获取新的对象。
 * 4、mapper接口没有实现类，但是mybatis会为这个接口生成一个代理对象。
 * 		（将接口和xml进行绑定）
 * 		EmployeeMapper empMapper =	sqlSession.getMapper(EmployeeMapper.class);
 * 5、两个重要的配置文件：
 * 		mybatis的全局配置文件：包含数据库连接池信息，事务管理器信息等...系统运行环境信息
 * 		sql映射文件：保存了每一个sql语句的映射信息：
 * 					将sql抽取出来。	
 * 
 * 
 * @author lfy
 *
 */
public class MyBatisTest {
	

	public SqlSessionFactory getSqlSessionFactory() throws IOException {
		String resource = "mybatis-config.xml";
		InputStream inputStream = Resources.getResourceAsStream(resource);
		return new SqlSessionFactoryBuilder().build(inputStream);
	}
	
	@Test
	public void testInnerParam() throws IOException{
		SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
		SqlSession openSession = sqlSessionFactory.openSession();
		try{
			EmployeeMapperDynamicSQL mapper = openSession.getMapper(EmployeeMapperDynamicSQL.class);
			Employee employee2 = new Employee();
			employee2.setLastName("%e%");
			List<Employee> list = mapper.getEmpsTestInnerParameter(employee2);
			for (Employee employee : list) {
				System.out.println(employee);
			}
		}finally{
			openSession.close();
		}
	}
	
	@Test
	public void testBatchSave() throws IOException{
		SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
		SqlSession openSession = sqlSessionFactory.openSession();
		try{
			EmployeeMapperDynamicSQL mapper = openSession.getMapper(EmployeeMapperDynamicSQL.class);
			List<Employee> emps = new ArrayList<>();
			emps.add(new Employee(null, "smith0x1", "[e-mail]", "1",new Department(1)));
			emps.add(new Employee(null, "allen0x1", "[e-mail]", "0",new Department(1)));
			mapper.addEmps(emps);
			openSession.commit();
		}finally{
			openSession.close();
		}
	}
	
	@Test
	public void testDynamicSql() throws IOException{
		SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
		SqlSession openSession = sqlSessionFactory.openSession();
		try{
			EmployeeMapperDynamicSQL mapper = openSession.getMapper(EmployeeMapperDynamicSQL.class);
			//select * from tbl_employee where id=? and last_name like ?
			//测试if\\where
			Employee employee = new Employee(1, "Admin", null, null);
		/*	List<Employee> emps = mapper.getEmpsByConditionIf(employee );
			for (Employee emp : emps) {
				System.out.println(emp);
			}*/
			
			//查询的时候如果某些条件没带可能sql拼装会有问题
			//1、给where后面加上1=1，以后的条件都and xxx.
			//2、mybatis使用where标签来将所有的查询条件包括在内。mybatis就会将where标签中拼装的sql，多出来的and或者or去掉
				//where只会去掉第一个多出来的and或者or。
			
			//测试Trim
			/*List<Employee> emps2 = mapper.getEmpsByConditionTrim(employee);
			for (Employee emp : emps2) {
				System.out.println(emp);
			}*/
			
			
			//测试choose
			/*List<Employee> list = mapper.getEmpsByConditionChoose(employee);
			for (Employee emp : list) {
				System.out.println(emp);
			}*/
			
			//测试set标签
			/*mapper.updateEmp(employee);
			openSession.commit();*/
			
			List<Employee> list = mapper.getEmpsByConditionForeach(Arrays.asList(1,2));
			for (Employee emp : list) {
				System.out.println(emp);
			}
			
		}finally{
			openSession.close();
		}
	}

	/**
	 * 1、根据xml配置文件（全局配置文件）创建一个SqlSessionFactory对象 有数据源一些运行环境信息
	 * 2、sql映射文件；配置了每一个sql，以及sql的封装规则等。 
	 * 3、将sql映射文件注册在全局配置文件中
	 * 4、写代码：
	 * 		1）、根据全局配置文件得到SqlSessionFactory；
	 * 		2）、使用sqlSession工厂，获取到sqlSession对象使用他来执行增删改查
	 * 			一个sqlSession就是代表和数据库的一次会话，用完关闭
	 * 		3）、使用sql的唯一标志来告诉MyBatis执行哪个sql。sql都是保存在sql映射文件中的。
	 * 
	 * @throws IOException
	 */
	@Test
	public void test() throws IOException {

		// 2、获取sqlSession实例，能直接执行已经映射的sql语句
		// sql的唯一标识：statement Unique identifier matching the statement to use.
		// 执行sql要用的参数：parameter A parameter object to pass to the statement.
		SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();

		SqlSession openSession = sqlSessionFactory.openSession();
		try {
			Employee employee = openSession.selectOne(
					"com.atguigu.mybatis.EmployeeMapper.selectEmp", 1);
			System.out.println(employee);
		} finally {
			openSession.close();
		}

	}

	@Test
	public void test01() throws IOException {
		// 1、获取sqlSessionFactory对象
		SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
		// 2、获取sqlSession对象
		SqlSession openSession = sqlSessionFactory.openSession();
		try {
			// 3、获取接口的实现类对象
			//会为接口自动的创建一个代理对象，代理对象去执行增删改查方法
			EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);
			Employee employee = mapper.getEmpById(1);
			System.out.println(mapper.getClass());
			System.out.println(employee);
		} finally {
			openSession.close();
		}

	}
	
	@Test
	public void test02() throws IOException{
		SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
		SqlSession openSession = sqlSessionFactory.openSession();
		try{
			EmployeeMapperAnnotation mapper = openSession.getMapper(EmployeeMapperAnnotation.class);
			Employee empById = mapper.getEmpById(1);
			System.out.println(empById);
		}finally{
			openSession.close();
		}
	}
	
	/**
	 * 测试增删改
	 * 1、mybatis允许增删改直接定义以下类型返回值
	 * 		Integer、Long、Boolean、void
	 * 2、我们需要手动提交数据
	 * 		sqlSessionFactory.openSession();===》手动提交
	 * 		sqlSessionFactory.openSession(true);===》自动提交
	 * @throws IOException 
	 */
	@Test
	public void test03() throws IOException{
		
		SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
		//1、获取到的SqlSession不会自动提交数据
		SqlSession openSession = sqlSessionFactory.openSession();
		
		try{
			EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);
			//测试添加
			Employee employee = new Employee(null, "jerry4",null, "1");
			mapper.addEmp(employee);
			System.out.println(employee.getId());
			
			//测试修改
			//Employee employee = new Employee(1, "Tom", "[e-mail]", "0");
			//boolean updateEmp = mapper.updateEmp(employee);
			//System.out.println(updateEmp);
			//测试删除
			//mapper.deleteEmpById(2);
			//2、手动提交数据
			openSession.commit();
		}finally{
			openSession.close();
		}
		
	}
	
	
	@Test
	public void test04() throws IOException{
		
		SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
		//1、获取到的SqlSession不会自动提交数据
		SqlSession openSession = sqlSessionFactory.openSession();
		
		try{
			EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);
			//Employee employee = mapper.getEmpByIdAndLastName(1, "tom");
			Map<String, Object> map = new HashMap<>();
			map.put("id", 2);
			map.put("lastName", "Tom");
			map.put("tableName", "tbl_employee");
			Employee employee = mapper.getEmpByMap(map);
			
			System.out.println(employee);
			
			/*List<Employee> like = mapper.getEmpsByLastNameLike("%e%");
			for (Employee employee : like) {
				System.out.println(employee);
			}*/
			
			/*Map<String, Object> map = mapper.getEmpByIdReturnMap(1);
			System.out.println(map);*/
			/*Map<String, Employee> map = mapper.getEmpByLastNameLikeReturnMap("%r%");
			System.out.println(map);*/
			
		}finally{
			openSession.close();
		}
	}
	
	@Test
	public void test05() throws IOException{
		SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
		SqlSession openSession = sqlSessionFactory.openSession();
		try{
			EmployeeMapperPlus mapper = openSession.getMapper(EmployeeMapperPlus.class);
			/*Employee empById = mapper.getEmpById(1);
			System.out.println(empById);*/
			/*Employee empAndDept = mapper.getEmpAndDept(1);
			System.out.println(empAndDept);
			System.out.println(empAndDept.getDept());*/
			Employee employee = mapper.getEmpByIdStep(3);
			System.out.println(employee);
			//System.out.println(employee.getDept());
			System.out.println(employee.getDept());
		}finally{
			openSession.close();
		}
		
		
	}
	
	@Test
	public void test06() throws IOException{
		SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
		SqlSession openSession = sqlSessionFactory.openSession();
		
		try{
			DepartmentMapper mapper = openSession.getMapper(DepartmentMapper.class);
			/*Department department = mapper.getDeptByIdPlus(1);
			System.out.println(department);
			System.out.println(department.getEmps());*/
			Department deptByIdStep = mapper.getDeptByIdStep(1);
			System.out.println(deptByIdStep.getDepartmentName());
			System.out.println(deptByIdStep.getEmps());
		}finally{
			openSession.close();
		}
	}	
	
}