200.Mybatis 的注解开发-CRUD

之前我们都是使用 XML 配置文件的方式来开发，虽然之前简单讲解过一点注解的开发，但是不多；本文就来将我们之前用的 XML 配置文件，全部替换成注解。 注意：注解 和 XML 不能混用，有注解就不能用 XML，会报错。

环境搭建

我们将除了 pom.xml 文件之外的文件都删掉，重新来搭建一次环境：

‍

新增 User 类

public class User implements Serializable {
    private Integer id;
    private String username;
    private String address;
    private String sex;
    private Date birthday;
}

请读者自行生成 getter 和 setter ‍

新建 Dao 接口

package com.peterjxl.dao;
import com.peterjxl.domain.User;
import java.util.List;
public interface IUserDao {
    List<User> findAll();
}

‍

新增主配置文件 SqlMapConfig.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <properties resource="jdbcConfig.properties"/>
    <typeAliases>
        <package name="com.peterjxl.domain"/>
    </typeAliases>
    <environments default="mysql">
        <environment id="mysql">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${jdbc.driver}"/>
                <property name="url" value="${jdbc.url}"/>
                <property name="username" value="${jdbc.username}"/>
                <property name="password" value="${jdbc.password}"/>
            </dataSource>
        </environment>
    </environments>
  
    <mappers>
        <package name="com.peterjxl.dao"/>
    </mappers>
</configuration>

‍

新建 log4j.properties

# Set root category priority to INFO and its only appender to CONSOLE.
#log4j.rootCategory=INFO, CONSOLE            debug   info   warn error fatal
log4j.rootCategory=debug, CONSOLE, LOGFILE

# Set the enterprise logger category to FATAL and its only appender to CONSOLE.
log4j.logger.org.apache.axis.enterprise=FATAL, CONSOLE

# CONSOLE is set to be a ConsoleAppender using a PatternLayout.
log4j.appender.CONSOLE=org.apache.log4j.ConsoleAppender
log4j.appender.CONSOLE.layout=org.apache.log4j.PatternLayout
log4j.appender.CONSOLE.layout.ConversionPattern=%d{ISO8601} %-6r [%15.15t] %-5p %30.30c %x - %m\n

# LOGFILE is set to be a File appender using a PatternLayout.
log4j.appender.LOGFILE=org.apache.log4j.FileAppender
log4j.appender.LOGFILE.File=d:\axis.log
log4j.appender.LOGFILE.Append=true
log4j.appender.LOGFILE.layout=org.apache.log4j.PatternLayout
log4j.appender.LOGFILE.layout.ConversionPattern=%d{ISO8601} %-6r [%15.15t] %-5p %30.30c %x - %m\n

新建 jdbcConfig.properties

jdbc.driver=com.mysql.cj.jdbc.Driver
jdbc.url=jdbc:mysql:///LearnMybatis
jdbc.username=LearnMybatisUser
jdbc.password=LearnMybatisUserPassword

‍

单表 CRUD 操作（代理 Dao 方式）

‍

新增 select 注解

package com.peterjxl.dao;
import com.peterjxl.domain.User;
import org.apache.ibatis.annotations.Select;
import java.util.List;
public interface IUserDao {
    @Select("select * from user")
    List<User> findAll();
}

新增测试类

package com.peterjxl;

import com.peterjxl.dao.IUserDao;
import com.peterjxl.domain.User;
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.After;
import org.junit.Before;
import org.junit.Test;

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

public class MybatisAnnoTest {

    private InputStream in;
    private SqlSessionFactoryBuilder builder;
    private SqlSessionFactory factory;
    private SqlSession session;
    private IUserDao userDao;

    @Before
    public void init() throws IOException {
        in = Resources.getResourceAsStream("SqlMapConfig.xml");
        builder = new SqlSessionFactoryBuilder();
        factory = builder.build(in);
        session = factory.openSession();
        userDao = session.getMapper(IUserDao.class);
    }

    @After
    public void destroy() throws IOException {
        session.commit();
        session.close();
        in.close();
    }

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

新增 Insert 注解

在接口新建方法

@Insert("insert into user(username, address, sex, birthday) values (#{username}, #{address}, #{sex}, #{birthday})")
void saveUser(User user);

‍ 新建测试方法：

@Test
public void testSaveUser(){
    User user = new User();
    user.setUsername("mybatis anno save user");
    user.setAddress("广州市番禺区");
    user.setSex("男");
    user.setBirthday(new Date());
    userDao.saveUser(user);
}

新增 Update 注解

@Update("update user set username=#{username}, address=#{address}, sex=#{sex}, birthday=#{birthday}  where id=#{id}")
void updateUser(User user);

‍ 测试方法：

@Test
public void testUpdate(){
    User user = new User();
    user.setId(41);
    user.setUsername("mybatis anno update user");
    user.setAddress("广州市番禺区");
    user.setSex("男");
    user.setBirthday(new Date());

    userDao.updateUser(user);
    session.commit();
}

‍

新增 Delete 注解

@Delete("delete from user where id=#{id}")
void deleteUser(Integer userId);

‍

@Test
public void testDelete(){
    userDao.deleteUser(56);
}

查询一个

@Select("select * from user where id=#{id}")
User findById(Integer id);

‍

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

‍

模糊查询

写法一：注意这里没写百分号，所以传入的参数要带百分号

@Select("select * from user where username like #{username}")
List<User> findUserByName(String username);

测试方法：

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

写法二：

@Select("select * from user where username like '%${value}%'")
List<User> findUserByName(String username);

‍ 此时传参就不用百分号了：

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

查询总数

@Select("select count(*) from user")
int findTotalUser();

‍

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

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 demo19，读者可以通过切换分支来查看本文的示例代码。