从01开始
2023-04-25
目录

Mybatis实现DAO层的开发

# 100.Mybatis实现DAO层的开发

通过之前的博客，我们对Mybatis的基本使用有了一定的认知，接下来我们实战下，用Mybatis实现DAO层的开发 　　‍

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# 自定义实现类

之前我们都是使用代理对象的方式，来完成数据库的CRUD，接下来我们继续讲解不通过代理对象，而是自己实现IUserDao接口的类里完成CRUD。

创建UserDaoImpl类，并实现findAll方法：

package com.peterjxl.dao.impl;

import com.peterjxl.dao.IUserDao;
import com.peterjxl.domain.QueryVo;
import com.peterjxl.domain.User;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;

import java.util.List;

public class UserDaoImpl implements IUserDao {

    private SqlSessionFactory factory;

    public UserDaoImpl(SqlSessionFactory factory){
        this.factory = factory;
    }

    @Override
    public List<User> findAll() {
        SqlSession session = factory.openSession();
        List<User> users = session.selectList("com.peterjxl.dao.IUserDao.findAll");
        session.close();
        return users;
    }

    @Override
    public void saveUser(User user) {

    }

    @Override
    public void updateUser(User user) {

    }

    @Override
    public void deleteUser(Integer userId) {

    }

    @Override
    public User findById(Integer userId) {
        return null;
    }

    @Override
    public List<User> findByName(String name) {
        return null;
    }

    @Override
    public int findTotal() {
        return 0;
    }

    @Override
    public List<User> findUserByVo(QueryVo vo) {
        return null;
    }
}
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# 新增测试类

为了和之前的代码区分开，这里新建了一个测试类MybatisTestImpl；

这里我们init方法和destory方法就简化了，只需要InputStream对象和一个IUserDao对象：

package com.peterjxl.test;

import com.peterjxl.dao.IUserDao;
import com.peterjxl.dao.impl.UserDaoImpl;
import com.peterjxl.domain.User;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

import java.io.IOException;
import java.io.InputStream;
import java.util.List;

public class MybatisTestImpl {

    private InputStream in;
    private IUserDao userDao;

    @Before
    public void init() throws IOException {
        in = Resources.getResourceAsStream("SqlMapConfig.xml");
        SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(in);
        userDao = new UserDaoImpl(factory);
    }

    @After
    public void destory() throws IOException {
        in.close();
    }

    @Test
    public void testFindAll(){
        List<User> users = userDao.findAll();
        for(User user : users){
            System.out.println(user);
        }
    }

}
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然后我们测试testFindAll，可以看到是能正常运行的，该案例其实我们之前也讲过。这里重新引出这一个案例，是为了再次告诉读者，使用自定义实现类的话，有很多重复的代码，例如获取session，资源的释放等。

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# 完善自定义实现类

这里我们继续完善实现类的其他方法：其实代码都差不多，QueryVo的方式我们就不演示了：

package com.peterjxl.dao.impl;

import com.peterjxl.dao.IUserDao;
import com.peterjxl.domain.QueryVo;
import com.peterjxl.domain.User;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;

import java.util.List;

public class UserDaoImpl implements IUserDao {

    private SqlSessionFactory factory;

    public UserDaoImpl(SqlSessionFactory factory){
        this.factory = factory;
    }

    @Override
    public List<User> findAll() {
        SqlSession session = factory.openSession();
        List<User> users = session.selectList("com.peterjxl.dao.IUserDao.findAll");
        session.close();
        return users;
    }

    @Override
    public void saveUser(User user) {
        SqlSession session = factory.openSession();
        session.insert("com.peterjxl.dao.IUserDao.saveUser", user);
        session.commit();
        session.close();
    }

    @Override
    public void updateUser(User user) {
        SqlSession session = factory.openSession();
        session.update("com.peterjxl.dao.IUserDao.updateUser", user);
        session.commit();
        session.close();
    }

    @Override
    public void deleteUser(Integer userId) {
        SqlSession session = factory.openSession();
        session.delete("com.peterjxl.dao.IUserDao.deleteUser", userId);
        session.commit();
        session.close();
    }

    @Override
    public User findById(Integer userId) {
        SqlSession session = factory.openSession();
        User u = session.selectOne("com.peterjxl.dao.IUserDao.findById", userId);
        session.close();
        return u;
    }

    @Override
    public List<User> findByName(String name) {
        SqlSession session = factory.openSession();
        List<User> users = session.selectList("com.peterjxl.dao.IUserDao.findByName", name);
        session.close();
        return users;
    }

    @Override
    public int findTotal() {
        SqlSession session = factory.openSession();
        int n = session.selectOne("com.peterjxl.dao.IUserDao.findTotal");
        session.close();
        return n;
    }

    @Override
    public List<User> findUserByVo(QueryVo vo) {
        return null;
    }
}
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# 测试其他方法

package com.peterjxl.test;

import com.peterjxl.dao.IUserDao;
import com.peterjxl.dao.impl.UserDaoImpl;
import com.peterjxl.domain.User;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

import java.io.IOException;
import java.io.InputStream;
import java.util.Date;
import java.util.List;

public class MybatisTestImpl {

    private InputStream in;
    private IUserDao userDao;

    @Before
    public void init() throws IOException {
        in = Resources.getResourceAsStream("SqlMapConfig.xml");
        SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(in);
        userDao = new UserDaoImpl(factory);
    }

    @After
    public void destory() throws IOException {
        in.close();
    }

    @Test
    public void testFindAll(){
        List<User> users = userDao.findAll();
        for(User user : users){
            System.out.println(user);
        }
    }

    @Test
    public void testSave() throws IOException {
        User user = new User();
        user.setUserName("dao impl user");
        user.setUserAddress("广州市番禺区");
        user.setUserSex("男");
        user.setUserBirthday(new Date());

        System.out.println("保存操作之前：: " + user);
        userDao.saveUser(user);
        System.out.println("保存操作之前：: " + user);
    }

    @Test
    public void testUpdate(){
        User user = new User();
        user.setUserId(41); //张三的数据
        user.setUserName("mybatis update impl user");
        user.setUserAddress("广州市番禺区");
        user.setUserSex("男");
        user.setUserBirthday(new Date());

        userDao.updateUser(user);
    }

    @Test
    public void testDelete(){
        userDao.deleteUser(55);
    }

    @Test
    public void testFindOne(){
        User user = userDao.findById(41);
        System.out.println(user);
    }


    @Test
    public void testFindByName(){
        List<User> users = userDao.findByName("mybatis%");
        for(User user : users){
            System.out.println(user);
        }
    }

    @Test
    public void testFindTotal(){
        int total = userDao.findTotal();
        System.out.println("total: " + total);
    }


}
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# 源码

所有代码已上传到了GitHub (opens new window)和Gitee (opens new window)上，并且创建了分支demo10，读者可以通过切换分支来查看本文的示例代码。

在GitHub上编辑此页 (opens new window)
上次更新: 2023/5/6 21:54:08
Mybatis中的列名和属性名的映射
Mybatis实现类的执行过程-查询方法

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