mybatis动态sql之分支选择(学习choose、when、otherwise标签)
时间:2022-07-23
本文章向大家介绍mybatis动态sql之分支选择(学习choose、when、otherwise标签),主要内容包括其使用实例、应用技巧、基本知识点总结和需要注意事项,具有一定的参考价值,需要的朋友可以参考一下。
EmployeeMapperDynamicSql.java
package com.gong.mybatis.mapper;
import java.util.List;
import java.util.Map;
import org.apache.ibatis.annotations.MapKey;
import com.gong.mybatis.bean.Employee;
public interface EmployeeMapperDynamicSql {
public List<Employee> getEmpByConditionIf(Employee employee);
}
EmployeeMapperDynamicSql.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="com.gong.mybatis.mapper.EmployeeMapperDynamicSql">
<!-- 查询,要查那个就带上那个条件 -->
<select id="getEmpByConditionIf" resultType="com.gong.mybatis.bean.Employee">
select * from tbl_employee
<where>
<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>
</otherwise>
</choose>
</where>
</select>
</mapper>
说明:当传入了id,就会根据id来查询,传入了lastName,就根据last_name来查询,传入了email,就根据email查询。否则就执行otherwise标签里面的。
测试:
package com.gong.mybatis.test;
import java.io.IOException;
import java.io.InputStream;
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.gong.mybatis.bean.Employee;
import com.gong.mybatis.mapper.EmployeeMapperDynamicSql;
public class TestMybatis3 {
public SqlSessionFactory getSqlSessionFactory() throws IOException {
String resource = "mybatis-config.xml";
InputStream is = Resources.getResourceAsStream(resource);
return new SqlSessionFactoryBuilder().build(is);
}
@Test
public void test() throws IOException {
SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
SqlSession openSession = sqlSessionFactory.openSession();
try {
EmployeeMapperDynamicSql mapper = openSession.getMapper(EmployeeMapperDynamicSql.class);
Employee employee = new Employee();
// employee.setId(3);
// employee.setLastName("%小%");
// employee.setEmail("xiaoming@qq.com");
List<Employee> es = mapper.getEmpByConditionIf(employee);
for(Employee e:es) {
System.err.println(e);
}
openSession.commit();
} finally {
openSession.close();
}
}
}
首先根据id=3进行查询:
DEBUG 01-21 13:45:17,288 ==> Preparing: select * from tbl_employee WHERE id=? (BaseJdbcLogger.java:145)
DEBUG 01-21 13:45:17,339 ==> Parameters: 3(Integer) (BaseJdbcLogger.java:145)
DEBUG 01-21 13:45:17,410 <== Total: 1 (BaseJdbcLogger.java:145)
Employee [id=3, lastName=小红, gender=0, email=xiaohong@qq.com, dept=null]
根据lastName="%小%"进行模糊查询:
DEBUG 01-21 13:46:04,385 ==> Preparing: select * from tbl_employee WHERE last_name like ? (BaseJdbcLogger.java:145)
DEBUG 01-21 13:46:04,417 ==> Parameters: %小%(String) (BaseJdbcLogger.java:145)
DEBUG 01-21 13:46:04,502 <== Total: 2 (BaseJdbcLogger.java:145)
Employee [id=3, lastName=小红, gender=0, email=xiaohong@qq.com, dept=null]
Employee [id=4, lastName=小明, gender=0, email=xiaoming@qq.com, dept=null]
根据email=xiximayou@qq.com进行查询:
DEBUG 01-21 13:46:43,284 ==> Preparing: select * from tbl_employee WHERE email=? (BaseJdbcLogger.java:145)
DEBUG 01-21 13:46:43,347 ==> Parameters: xiximayou@qq.com(String) (BaseJdbcLogger.java:145)
Employee [id=1, lastName=xiximayou, gender=1, email=xiximayou@qq.com, dept=null]
DEBUG 01-21 13:46:43,394 <== Total: 1 (BaseJdbcLogger.java:145)
根据id=3,lastName=%小%进行查询:
DEBUG 01-21 13:47:30,447 ==> Preparing: select * from tbl_employee WHERE id=? (BaseJdbcLogger.java:145)
DEBUG 01-21 13:47:30,522 ==> Parameters: 3(Integer) (BaseJdbcLogger.java:145)
DEBUG 01-21 13:47:30,553 <== Total: 1 (BaseJdbcLogger.java:145)
Employee [id=3, lastName=小红, gender=0, email=xiaohong@qq.com, dept=null]
不输入任何参数,默认查询:
DEBUG 01-21 14:18:25,159 ==> Preparing: select * from tbl_employee (BaseJdbcLogger.java:145)
DEBUG 01-21 14:18:25,243 ==> Parameters: (BaseJdbcLogger.java:145)
DEBUG 01-21 14:18:25,274 <== Total: 4 (BaseJdbcLogger.java:145)
Employee [id=1, lastName=xiximayou, gender=1, email=xiximayou@qq.com, dept=null]
Employee [id=2, lastName=jack, gender=1, email=675544321@qq.com, dept=null]
Employee [id=3, lastName=小红, gender=0, email=xiaohong@qq.com, dept=null]
Employee [id=4, lastName=小明, gender=0, email=xiaoming@qq.com, dept=null]
此时就会查询出所有的数据。
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