SpringBoot 整合Mybatis (2) 通过注解调用S

文件结构目录：
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pom.xml：

添加mybatis、mysql、web依赖，这里的mybatis会关联jdbc的依赖，所以可以不添加jdbc的依赖。web只是为了方便测试，并非必须。

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.bingo</groupId>
    <artifactId>springbootmybatis-anno</artifactId>
    <version>1.0-SNAPSHOT</version>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.6.RELEASE</version>
    </parent>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <!--mybatis -->
        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
            <version>1.3.2</version>
        </dependency>

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
        </dependency>
    </dependencies>


</project>

在resources资源文件夹中添加application.yml：

spring:
  datasource:
    url: jdbc:mysql://localhost:3306/springbootmybatis?characterEncoding=UTF-8&useSSL=false
    username: root
    password: 123456
    driver-class-name: com.mysql.jdbc.Driver

mybatis:
  type-aliases-package: com.demo.pojo

添加实体类：
这里如果getter和setter方法的名称与数据库中存放的一致，则能够自动和数据库映射匹配，这边设置成一致。这边不会有驼峰命名到下划线命名的这种转换关系。一旦有一个不匹配，直接该不匹配的返回null，其余的仍然能正常得到数据。

package com.demo.pojo;

// 会根据getter和setter方法名称和数据库成员名字进行匹配
// 如果一致，那么无需额外配置
public class User {

    private Integer id;
    private String username;
    private String password;
    private String realname;

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public String getRealname() {
        return realname;
    }

    public void setRealname(String realname) {
        this.realname = realname;
    }
}

添加mapper接口：
利用注解添加方法。

package com.demo.mapper;


import com.demo.pojo.User;
import org.apache.ibatis.annotations.*;

import java.util.List;


@Mapper
public interface UserMapper{

    @Select("select * from user where id = #{id}")
    User selectByPrimaryKey(@Param("id") int id);

    @Select("select * from user")
    List<User> selectAll();

    @Delete("delete from user where id = #{id}")
    int deleteByPrimaryKey(@Param("id") int id);

    @Update("update user set username = #{username}, password = #{password}, realname = #{realname} where id = #{id}")
    int update(@Param("id") int id, @Param("username") String username, @Param("password") String password, @Param("realname") String realname);

    @Insert("insert into user(username, password) values(#{username}, #{password})")
    int insert(@Param("username") String username, @Param("password") String password);
}

添加引导类：

package com.demo;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class ApplicationBoot {
    public static void main(String[] args) {
        SpringApplication.run(ApplicationBoot.class, args);
    }
}

定义service接口：
定义增删改查的抽象方法。

package com.demo.service;

import com.demo.pojo.User;

import java.util.List;


public interface UserService {

    /**
     * 根据id查询某一个具体的User
     *
     * @param id
     * @return
     */
    User queryById(int id);

    /**
     * 查询全体User信息
     *
     * @return
     */
    List<User> queryAll();

    /**
     * 根据id删除掉某个User
     *
     * @param id
     * @return
     */
    int deleteById(int id);

    /**
     * 更新一个用户信息
     *
     * @param id
     * @param username
     * @param password
     * @param realname
     * @return
     */
    int updateUser(int id, String username, String password, String realname);

    /**
     * 添加一个用户
     *
     * @param username
     * @param password
     * @return
     */
    int insertUser(String username, String password);

}

定义service的实现类：
调用Mapper类里面提供的方法，来执行SQL语句。

package com.demo.service.impl;

import com.demo.mapper.UserMapper;
import com.demo.pojo.User;
import com.demo.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import java.util.List;

@Service
public class UserServiceImpl implements UserService {

    @Autowired
    private UserMapper userMapper;


    @Override
    public User queryById(int id) {
        return this.userMapper.selectByPrimaryKey(id);
    }

    @Override
    public List<User> queryAll() {
        return this.userMapper.selectAll();
    }

    @Override
    @Transactional
    public int deleteById(int id) {
        return this.userMapper.deleteByPrimaryKey(id);
    }

    @Override
    @Transactional
    public int updateUser(int id, String username, String password, String realname) {
        return this.userMapper.update(id, username, password, realname);
    }

    @Override
    @Transactional
    public int insertUser(String username, String password) {
        return this.userMapper.insert(username, password);
    }
}

写controller层进行测试：

package com.demo.controller;

import com.demo.pojo.User;
import com.demo.service.impl.UserServiceImpl;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;

import java.util.List;


// 用于测试
@RestController
@RequestMapping("user")
public class UserController {

    @Autowired
    private UserServiceImpl userServiceImpl;

    // select
    @RequestMapping(value = "/all", method = RequestMethod.GET)
    public List<User> getAllUsers() {
        return userServiceImpl.queryAll();
    }

    // select
    @RequestMapping(value = "/{id}", method = RequestMethod.GET)
    public User getUserById(@PathVariable("id") int id) {
        return userServiceImpl.queryById(id);
    }

    // update
    @RequestMapping(value = "/{id}", method = RequestMethod.PUT)
    public String updateAccount(@PathVariable("id") int id,
                                @RequestParam(value = "username", required = true) String username,
                                @RequestParam(value = "password", required = true) String password,
                                @RequestParam(value = "realname", required = true) String realname) {
        int t = userServiceImpl.updateUser(id, username, password, realname);
        if (t == 1) {
            return "success";
        } else {
            return "fail";
        }

    }

    // delete
    @RequestMapping(value = "/{id}", method = RequestMethod.DELETE)
    public String delete(@PathVariable(value = "id") int id) {
        int t = userServiceImpl.deleteById(id);
        if (t == 1) {
            return "success";
        } else {
            return "fail";
        }

    }

    // post
    @RequestMapping(value = "", method = RequestMethod.POST)
    public String postAccount(@RequestParam(value = "username") String username,
                              @RequestParam(value = "password") String password) {

        int t = userServiceImpl.insertUser(username, password);
        if (t == 1) {
            return "success";
        } else {
            return "fail";
        }

    }


    @GetMapping("hello")
    public String test() {
        return "hello mybatis";
    }
    
}

补充说明：
如果实体类名称和数据库名称不匹配(准确地说是getter和setter方法名和数据库不匹配)，可以通过以下方法来解决（这里我把username改成了name）：
得到的结果：

修改方法：
在mapper接口中添加@Results和@Result

package com.demo.mapper;


import com.demo.pojo.User;
import org.apache.ibatis.annotations.*;

import java.util.List;


@Mapper
public interface UserMapper {

    @Results({
            @Result(property = "id", column = "id"),
            @Result(property = "name", column = "username"),
            @Result(property = "password", column = "password"),
            @Result(property = "realname", column = "realname")
    })

    @Select("select * from user where id = #{id}")
    User selectByPrimaryKey(@Param("id") int id);

    @Select("select * from user")
    List<User> selectAll();

    @Delete("delete from user where id = #{id}")
    int deleteByPrimaryKey(@Param("id") int id);

    @Update("update user set username = #{username}, password = #{password}, realname = #{realname} where id = #{id}")
    int update(@Param("id") int id, @Param("username") String username, @Param("password") String password, @Param("realname") String realname);

    @Insert("insert into user(username, password) values(#{username}, #{password})")
    int insert(@Param("username") String username, @Param("password") String password);
}

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