mybatis中xml映射文件（mybatis配置文件mapper映射）

Mapper映射文件是一个xml格式文件，必须遵循相应的dtd文件规范

在学习mybatis的时候我们通常会在映射文件这样写：

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<?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：

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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

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<?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：

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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

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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：

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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

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原文链接：https://blog.csdn.net/two_people/article/details/51759881