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这篇文章主要介绍“mybatis的映射文件mapper.xml怎么写”，在日常操作中，相信很多人在mybatis的映射文件mapper.xml怎么写问题上存在疑惑，小编查阅了各式资料，整理出简单好用的操作方法，希望对大家解答”mybatis的映射文件mapper.xml怎么写”的疑惑有所帮助！接下来，请跟着小编一起来学习吧！
在学习mybatis的时候我们通常会在映射文件这样写：
<?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.qbd.mapper.StudentMappers">
<select id="findbyid" parameterType="Integer" resultMap="StudentResult">
select *from student where id=#{id}
</select>
<select id="findbygradeid" parameterType="Integer" resultMap="StudentResult">
select *from student where gid=#{gid}
</select>
<resultMap type="Student" id="StudentResult">
<id property="id" column="id"/>
<result property="name" column="name"/>
<result property="age" column="age"/>
<association property="address" column="addid" select="com.qbd.mapper.AddressMappers.findbyid">
</association>
<association property="grade" column="gid" select="com.qbd.mapper.GradeMappers.findbyid">
</association>
</resultMap>
</mapper>然后再写dao的实现在写一个类，来实现dao的接口。但是这样在实现中需要这样写：
package com.qbd.service;
import org.apache.ibatis.session.SqlSession;
import org.apache.log4j.Logger;
import com.qbd.mapper.StudentMappers;
import com.qbd.model.Student;
import com.qbd.util.SqlSessionFactoryUtil;
public class StudentService {
private static Logger logge=Logger.getLogger(StudentService.class);
public static void main(String[] args) {
SqlSession sqlSession=SqlSessionFactoryUtil.getSqlSession();
StudentMappers studentMappers=(StudentMappers)sqlSession.getMapper(StudentMappers.class);
Student student=new Student();
student.setName("22");
student.setAge(2);
int s=studentMappers.add(student);
sqlSession.commit();
if(s>0){
logge.info("success");
System.out.println("success");
}
}
}来读取配置文件
另一种方法就是：
直接在mapper.xml中的这一部分写成dao<mapper namespace="com.qbd.mapper.StudentMappers">如下
<?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.qbd.ssm.dao.UserDao">
<!-- 定义缓存 一般是一级缓存，如果用同一个sqlsession 那么相同查询直接会从缓存中查找
<cache size="1024" flushInterval="60000" eviction="LRU" readOnly="false"></cache>
-->
<!-- 查找所有 -->
<select id="find" parameterType="Map" resultMap="StudentResult">
select * from user
<where>
<if test="uname!=null and uname!='' ">
and uname like #{uname}
</if>
</where>
<if test="start!=null and size!=null">
limit #{start},#{size}
</if>
</select>
<select id="getTotal" parameterType="Map" resultType="Long">
select count(*) from user
<where>
<if test="uname!=null and uname!='' ">
and uname like #{uname}
</if>
</where>
</select>
<!-- 按照用户名和密码查找 -->
<select id="getUser" resultMap="StudentResult" parameterType="Map">
select *from user where uname=#{uname} and upassword=#{upassword}
</select>
<!-- 删除 -->
<delete id="delete" parameterType="Map">
delete from user where uid=#{uid}
</delete>
<!-- 修改 -->
<update id="update" parameterType="User">
update user
<set>
<if test="uname!=null">
uname=#{uname},
</if>
<if test="upassword!=null">
upassword=#{upassword},
</if>
<if test="upower!=null">
upower=#{upower},
</if>
</set>
where uid=#{uid}
</update>
<!-- 增加 -->
<insert id="add" parameterType="User">
insert into user values(null,#{uname},#{upassword},#{upower})
</insert>
<resultMap type="User" id="StudentResult">
<id property="uid" column="uid"/>
<result property="uname" column="uname"/>
<result property="upassword" column="upassword"/>
</resultMap>
</mapper>那么就不用写dao的实现在service中就能掉用 mybatis默认会把mapper.xml映射为dao的实现
那么下面dao就能这样写：
package com.qbd.ssm.dao;
import java.util.List;
import java.util.Map;
import org.apache.ibatis.annotations.Delete;
import com.qbd.ssm.model.User;
public interface UserDao {
public List<User> getAll();
public User getUser(User user);
public int delete(User user);
public int update(User user);
public int add(User user);
public List<User> find(Map<String,Object> map);
public Long getTotal(Map<String,Object> map);
}service这样写
package com.qbd.ssm.service;
import java.util.List;
import java.util.Map;
import com.qbd.ssm.model.User;
public interface UserService {
public List<User> getAll();
public User getUser(User user);
public int delete(User user);
public int update(User user);
public int add(User user);
public List<User> find(Map<String,Object> map);
public Long getTotal(Map<String,Object> map);
}service的实现：
package com.qbd.ssm.serviceimpl;
import java.util.List;
import java.util.Map;
import javax.annotation.Resource;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import com.qbd.ssm.dao.UserDao;
import com.qbd.ssm.model.User;
import com.qbd.ssm.service.UserService;
@Service("userService")
public class UserServiceImpl implements UserService {
private UserDao userDao;
public UserDao getUserDao() {
return userDao;
}
@Resource
public void setUserDao(UserDao userDao) {
this.userDao = userDao;
}
public List<User> getAll() {
// TODO Auto-generated method stub
return userDao.getAll();
}
public User getUser(User user) {
// TODO Auto-generated method stub
return userDao.getUser(user);
}
public int delete(User user) {
// TODO Auto-generated method stub
return userDao.delete(user);
}
public int update(User user) {
// TODO Auto-generated method stub
return userDao.update(user);
}
public int add(User user) {
// TODO Auto-generated method stub
return userDao.add(user);
}
public List<User> find(Map<String, Object> map) {
// TODO Auto-generated method stub
return userDao.find(map);
}
public Long getTotal(Map<String, Object> map) {
// TODO Auto-generated method stub
return userDao.getTotal(map);
}
}在这里面userDao不能写错，spring会按照name进行注入
到此，关于“mybatis的映射文件mapper.xml怎么写”的学习就结束了，希望能够解决大家的疑惑。理论与实践的搭配能更好的帮助大家学习，快去试试吧！若想继续学习更多相关知识，请继续关注亿速云网站，小编会继续努力为大家带来更多实用的文章！
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