1.在pom文件中导入依赖
<!--导入log4j-->
<!-- https://mvnrepository.com/artifact/log4j/log4j -->
<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
<version>1.2.17</version>
</dependency>
2.配置log4j.properties文件(配置在类路径下，resource目录下)
#将等级为DEBUG的日志信息输出到console和file这两个目的地
，console和file的定义在下面的代码
log4j.rootLogger=DEBUG,console,file
#控制台输出的相关设置
log4j.appender.console=org.apache.log4j.ConsoleAppender
log4j.appender.console.Target=System.out
log4j.appender.console.Threshold=DEBUG
log4j.appender.console.layout=org.apache.log4j.PatternLayout
log4j.appender.console.layout.ConversionPattern=[%c]-%m%n
#输出到日志文件
log4j.appender.file=org.apache.log4j.RollingFileAppender
log4j.appender.file.File=./log/Mybatis_logs.log
log4j.appender.file.Threshold=DEBUG
log4j.appender.file.layout=org.apache.log4j.PatternLayout
log4j.appender.file.layout.ConversionPattern=[%p][%d{yyyy-MM-dd}][%c]%m%n
#日志输出级别
log4j.logger.org.mybatis=DEBUG
log4j.logger.java.sql=DEBUG
log4j.logger.java.sql.Statement=DEBUG
log4j.logger.java.sql.ResultSet=DEBUG
log4j.logger.java.sql.PreparedStatement=DEBUG
3.成果展示
/*实现分页查询*/
List<UserPojo> getLimitUser(HashMap<String, Integer> map);
2.UserMapper.xml
<!--ResultMap 结果集,解决数据库列名与属性名不同的问题-->
<resultMap id="UserMap" type="UserAliasesType">
<!--这里的ID和Name都可以省略-->
<id column="id" property="id"/>
<result column="name" property="name"/>
<result column="password" property="pwd"/>
</resultMap>
<!--分页查询-->
<select id="getLimitUser" parameterType="Map" resultMap="UserMap" >
select * from `user` limit #{indexPage},#{countPage}
</select>
3.UserMapperTest.class
//第一种方式
/*分页查询*/
@Test
public void getLimitUserTest() throws IOException {
SqlSession sqlsession = MybatisUtil.getSQLSession();
UserMapper mapper = sqlsession.getMapper(UserMapper.class);
HashMap<String,Integer> map = new HashMap<String, Integer>();
map.put("indexPage",0);
map.put("countPage",5);
List<UserPojo> limitUser = mapper.getLimitUser(map);
for (UserPojo user:limitUser) {
System.out.println(user);
}
//第二种方式：使用RowBounds
@Test
public void getLimiterRoeBounds(){
RowBounds rowBounds = new RowBounds(5, 5);
List<UserPojo> listuser = sqlsession.selectList("com.test.mapper.UserMapper.getListUser", null, rowBounds);
for (UserPojo user:listuser) {
System.out.println(user);
}
}
1.面向接口编程
作用：解耦、可扩展、提高复用性、分层开发（上层不用管下层的具体实现）、使得共同协作变得更加容易代码更具有规范性
2.操作(中间会用到MybatisUtil.class,mybatis-config.xml,log4j.properties,UserPojo.class)
需要在mybatis-config.xml文件中绑定接口(注册Mapper)
mybatis-config.xml
<!--注册Mapper-->
<mappers>
<!--第一种配置方式-->
<!--<mapper resource="com/test/mapper/UserMapper.xml"/>-->
<!--第二种配置方式(需要UserMapper.class文件与UserMapper.xml文件在同一个包下，且文件名必须相同)-->
<!--<mapper class="com.test.mapper.StudentMapper"/>-->
<mapper class="test.mapper.UserMapper"/>
<!--第三种配置方式(需要UserMapper.class文件与UserMapper.xml文件在同一个包下，且文件名必须相同)-->
<!--<package name="com.test.mapper"/>-->
</mappers>
UserMapper.class
package test.mapper;
import org.apache.ibatis.annotations.Insert;
import org.apache.ibatis.annotations.Param;
import org.apache.ibatis.annotations.Select;
import org.apache.ibatis.annotations.Update;
import test.pojo.UserPojo;
import java.util.HashMap;
import java.util.List;
public interface UserMapper {
//查询所有用户
@Select("select id,name,password pwd from user")
List<UserPojo> getListUser();
//添加用户
@Insert("insert into user values(#{id},#{name},#{pwd})")
int addUser(UserPojo userPojo);
//更新用户
@Update("update user set name=#{name},password=#{pwd} where id=#{id}")
int updateUser(UserPojo userPojo);
}
UserMapperTest.class
package com.test.mapper;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;
import test.mapper.UserMapper;
import test.pojo.UserPojo;
import test.util.MybatisUtil;
import java.io.IOException;
import java.util.List;
public class UserMapperTest {
SqlSession sqlSession;
UserMapper mapper;
public UserMapperTest() throws IOException {
this.sqlSession = MybatisUtil.getSQLSession();
this.mapper = sqlSession.getMapper(UserMapper.class);
}
//使用注解查询用户
@Test
public void getListUser(){
List<UserPojo> listUser = mapper.getListUser();
for (UserPojo user:listUser) {
System.out.println(user);
}
}
//使用注解添加用户
@Test
public void addUser(){
UserPojo userpojo = new UserPojo(3000, "2wubai", "2000");
int i = mapper.addUser(userpojo);
if(i==1) {
System.out.println("成功添加" + i + "行，数据！");
}else {
System.out.println("添加用户失败！");
}
}
//更新用户Byid
@Test
public void updateUser(){
UserPojo userpojo = new UserPojo(2000, "2000", "2000duo");
int i = mapper.updateUser(userpojo);
if(i==1) {
System.out.println("成功更新" + i + "行，数据！");
}else {
System.out.println("更新用户失败！");
}
}
}
学生表，老师表
实体类：
StudentMapper.class
package test.pojo;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
@Data //get，set方法
@AllArgsConstructor
@NoArgsConstructor
public class StudentPojo {
private int id;
private String name;
private TeacherPojo teacherPojo;
}
TeacherMapper.class
package test.pojo;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
@Data
@AllArgsConstructor
@NoArgsConstructor
public class TeacherPojo {
private int id;
private String name;
}
1.方法一：使用子查询
目标：查询有老师的学生
StudentMapper.class
public interface StudentMapper {
//ResultMap-多对一
List<StudentPojo> getUserAndTeacher();
}
StudentMapper.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">
<!--namespace相当于(UserMapperImpl)实现dao层接口-->
<mapper namespace="test.mapper.StudentMapper">
<!--创建ResultMap-->
<!--association:应用于对象，一般用于多对一
collection：应用于集合，一般用于一对多
-->
<resultMap id="studentMap" type="StudentAliasesType">
<association property="teacherPojo" column="tid" javaType="TeacherAliasesType" select="getTeacher"/>
<!--<collection property=""/>-->
</resultMap>
<select id="getUserAndTeacher" resultMap="studentMap">
select * from student;
</select>
<select id="getTeacher" resultType="TeacherAliasesType">
select * from teacher where id=#{tid}
</select>
</mapper>
StudentMapper.class
package com.test.mapper;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;
import test.mapper.StudentMapper;
import test.mapper.UserMapper;
import test.pojo.StudentPojo;
import test.util.MybatisUtil;
import java.io.IOException;
import java.util.List;
public class StudentMapperTest {
SqlSession sqlSession;
StudentMapper studentMapper;
public StudentMapperTest() throws IOException {
this.sqlSession = MybatisUtil.getSQLSession();
this.studentMapper = sqlSession.getMapper(StudentMapper.class);
}
//ResultMap多对一(子查询)
@Test
public void getUserAndTeacher(){
List<StudentPojo> userAndTeacher = studentMapper.getUserAndTeacher();
for (StudentPojo student:userAndTeacher) {
System.out.println(student);
}
sqlSession.close();
}
}
运行结果：
2.方法二：使用联表查询（与方法一的区别，主要是xml中的sql语句和resultMap配置的区别）
<!--使用联表查询-->
<resultMap id="Student2" type="StudentAliasesType">
<id property="id" column="id"/>
<id property="name" column="name"/>
<association property="teacherPojo" javaType="TeacherAliasesType">
<result property="name" column="tname"/>
</association>
</resultMap>
<select id="getStudentAndTeacher2" resultMap="Student2">
SELECT s.id,s.name,t.name tname FROM student s,teacher t where s.tid=t.id
</select>
1.测试环境：查询一个老师的所有学生
2.TeacherPojo.class中包含一个学生集合（List
3.与多对一基本一样，只有StudentPojo.class、TeacherPojo.class和TeacherMapper.xml不一样
StudentPojo.class
public class StudentPojo {
private int id;
private String name;
//private TeacherPojo teacherPojo;
private int tid;
}
TeacherPojo.class
public class TeacherPojo {
private int id;
private String name;
private List<StudentPojo> studentPojoList;
}
TeacherMapper.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">
<!--namespace相当于(UserMapperImpl)实现dao层接口-->
<mapper namespace="test.mapper.TeacherMapper">
<!--创建ResultMap-->
<!--association:应用于对象，一般用于多对一
collection：应用于集合，一般用于一对多
-->
<resultMap id="teacherMap" type="TeacherAliasesType">
<result property="id" column="id"/>
<result property="name" column="name"/>
<collection property="studentPojoList" ofType="StudentAliasesType">
<result property="id" column="id"/>
<result property="name" column="sname"/>
</collection>
<!--<collection property=""/>-->
</resultMap>
<select id="getTeacherAndStudentById" resultMap="teacherMap">
select t.id,t.name,s.name sname from teacher t,student s where t.id=s.tid and t.id=#{id}
</select>
<!--使用子查询的模式-->
<resultMap id="teacherMap2" type="TeacherAliasesType">
<result property="id" column="id"/>
<result property="name" column="name"/>
<collection property="studentPojoList" javaType="ArrayList" ofType="StudentAliasesType" select="getStudent" column="tid">
</collection>
</resultMap>
<select id="getTeacherAndStudentById2" resultMap="teacherMap2">
select id,name from teacher where id=#{id}
</select>
<select id="getStudent" resultType="StudentAliasesType">
select id,name from student where tid=#{tid}
</select>
</mapper>
TeacherMapperTest.class
public class TeacherMapperTest {
SqlSession sqlSession;
StudentMapper studentMapper;
TeacherMapper teacherMapper;
public TeacherMapperTest() throws IOException {
this.sqlSession = MybatisUtil.getSQLSession();
this.studentMapper = sqlSession.getMapper(StudentMapper.class);
this.teacherMapper = sqlSession.getMapper(TeacherMapper.class);
}
//一对多
@Test
public void getTeacherAndStudentById() {
List<TeacherPojo> teacherAndStudentById = teacherMapper.getTeacherAndStudentById(1);
for (TeacherPojo teacherandstudent : teacherAndStudentById) {
System.out.println(teacherandstudent);
}
}
@Test
public void getTeacherAndStudentById2() {
List<TeacherPojo> teacherAndStudentById = teacherMapper.getTeacherAndStudentById(1);
for (TeacherPojo teacherandstudent : teacherAndStudentById) {
System.out.println(teacherandstudent);
}
}
}
Mybatis-分页、注解、log4j的使用、ResultMap多对一和一对多
原文：https://www.cnblogs.com/Gpengbolg/p/14905503.html