创建springboot+mybatis项目详细版全过程

1.创建一个springboot的maven项目（完成图中勾选处后，一路next继续）

设置项目的元数据，第一个是包结构（Group），第二个是项目标识（Artifact）：

添加项目所需要的依赖，Web的依赖和数据库的依赖：

第一次建立项目，需要下载许多包，请耐心等待一下。最后pom.xml如下：

    4.0.0
    
        org.springframework.boot
        spring-boot-starter-parent
        2.1.4.RELEASE
         
    
    com.ljy.project
    springdemo
    0.0.1-SNAPSHOT
    springdemo
    Demo project for Spring Boot

    
        1.8
    

    
        
            org.springframework.boot
            spring-boot-starter-jdbc
        
        
            org.springframework.boot
            spring-boot-starter-web
        
        
            org.mybatis.spring.boot
            mybatis-spring-boot-starter
            2.0.1
        

        
            mysql
            mysql-connector-java
            runtime
        
        
            org.springframework.boot
            spring-boot-starter-test
            test
        
    

    
        
            
                org.springframework.boot
                spring-boot-maven-plugin
            
        
    

手动添加的dependency需要 右键pom.xml->Maven->Reimport导入依赖。

2.在启动类同级目录下创建domain,dao,service,controller四个目录

在domain文件夹下创建User类：

 

package com.ljy.project.springdemo.domain;

public class User {
    private String username;
    private String password;
    private String patternLock;

    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 getPatternLock() {
        return patternLock;
    }

    public void setPatternLock(String patternLock) {
        this.patternLock = patternLock;
    }
}

然后在dao文件夹下创建UserDao接口：

package com.ljy.project.springdemo.dao;

import com.ljy.project.springdemo.domain.User;
import org.apache.ibatis.annotations.Mapper;
import org.apache.ibatis.annotations.Select;

import java.util.List;

@Mapper
public interface UserDao {

//    List selectUsers();

    @Select("select * from user")
    public List getAllUsers();
}

在service文件夹下创建UserService接口：

package com.ljy.project.springdemo.service;

import com.ljy.project.springdemo.dao.UserDao;
import com.ljy.project.springdemo.vo.ResultVo;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

@Service
public interface UserService {

    public ResultVo getAllUsers();
    
}

该结果返回值类型为ResultVo，在启动类同级目录下创建vo视图文件夹，在vo文件夹下创建ResultVo视图：

package com.ljy.project.springdemo.vo;

/*http请求返回的最外层对象*/
public class ResultVo {

    private Integer code;

    private String msg;

    private T data;

    private ResultVo(T data){
        this.code = 0;
        this.msg = "success";
        this.data = data;
    }

    private ResultVo(CodeMsg cm){
        if(cm==null){
            return;
        }else {
            this.code = cm.getCode();
            this.msg = cm.getMsg();
            this.data = null;
        }
    }

    public static  ResultVo success(T data){
        return new ResultVo(data);
    }

    public static  ResultVo error(CodeMsg cm){
        return new ResultVo(cm);
    }

    public Integer getCode() {
        return code;
    }

    public void setCode(Integer code) {
        this.code = code;
    }

    public String getMsg() {
        return msg;
    }

    public void setMsg(String msg) {
        this.msg = msg;
    }

    public T getData() {
        return data;
    }

    public void setData(T data) {
        this.data = data;
    }
}

在vo文件夹下创建CodeMsg错误码视图：

package com.ljy.project.springdemo.vo;

public class CodeMsg {

    private int code;
    private String msg;

    //错误码
    public static CodeMsg SUCCESS = new CodeMsg(0,"success");
    public static CodeMsg INSERT_ERROR = new CodeMsg(100001,"插入失败");
    public static CodeMsg SELECT_ERROR = new CodeMsg(100002,"查询失败");
    public static CodeMsg UPDATE_ERROR = new CodeMsg(100003,"更新失败");

    public CodeMsg(int code, String msg) {
        this.code = code;
        this.msg = msg;
    }

    public int getCode() {
        return code;
    }

    public void setCode(int code) {
        this.code = code;
    }

    public String getMsg() {
        return msg;
    }

    public void setMsg(String msg) {
        this.msg = msg;
    }
}

在service文件夹下创建Impl文件夹，在Impl文件夹下创建UserServiceImpl实现类：

package com.ljy.project.springdemo.service.Impl;

import com.ljy.project.springdemo.dao.UserDao;
import com.ljy.project.springdemo.domain.User;
import com.ljy.project.springdemo.service.UserService;
import com.ljy.project.springdemo.vo.CodeMsg;
import com.ljy.project.springdemo.vo.ResultVo;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.util.List;

@Service
public class UserServiceImpl implements UserService {

    @Autowired
    UserDao userDao;

    @Override
    public ResultVo getAllUsers() {
        List allUsers = userDao.getAllUsers();
        if(allUsers.size()==0){
            return ResultVo.error(CodeMsg.SELECT_ERROR);
        }else{
            return ResultVo.success(allUsers);
        }
    }
}

此处别忘了加@Service注解，我忘加了，运行时报如下错误：

Description:

Field userService in com.ljy.project.springdemo.controller.UserController required a bean of type 'com.ljy.project.springdemo.service.UserService' that could not be found.

The injection point has the following annotations:
	- @org.springframework.beans.factory.annotation.Autowired(required=true)


Action:

Consider defining a bean of type 'com.ljy.project.springdemo.service.UserService' in your configuration.

Disconnected from the target VM, address: '127.0.0.1:54425', transport: 'socket'

Process finished with exit code 1

在controller文件夹下创建UserController类：

package com.ljy.project.springdemo.controller;

import com.ljy.project.springdemo.dao.UserDao;
import com.ljy.project.springdemo.domain.User;
import com.ljy.project.springdemo.service.UserService;
import com.ljy.project.springdemo.vo.ResultVo;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import javax.xml.ws.RequestWrapper;
import java.util.List;

@RestController
@RequestMapping(value = "/try")
@EnableAutoConfiguration
public class UserController {

//    @Autowired
//    private UserDao userDao;

    @Autowired
    private UserService userService;

//    @RequestMapping(value = "/user")
//    public List getUsers(){
//        return userDao.selectUsers();
//    }

    @RequestMapping(value = "/getAll")
    public ResultVo getAllUsers(){
        return userService.getAllUsers();
    }
}

3.创建数据库（与domain中的实体类对应）

create table User
(
  id          int auto_increment
    primary key,
  username    varchar(20)  null,
  password    varchar(500) null,
  patternlock varchar(30)  null
);

向数据库中插入测试数据：

insert into User(username, password, patternlock) values ('zhangsan','123456','123456');
insert into User(username, password, patternlock) values ('lisi','123456','123456');
insert into User(username, password, patternlock) values ('wangwu','123456','123456');

4.在application.properties里面进行配置

spring.datasource.url=jdbc:mysql://127.0.0.1:3306/你的数据库名?useUnicode=true&characterEncoding=UTF-8&serverTimezone=GMT
spring.datasource.username=你的用户名
spring.datasource.password=你的密码
spring.datasource.driver-class-name=com.mysql.jdbc.Driver
 
mybatis.typeAliasesPackage=你的实体类包名 （例子项目的包名是com.ljy.project.springdemo.domain）
mybatis.mapperLocations=classpath:mapper/*.xml
logging.level.com.shizhao.project.springdemo:DEBUG
server.port=你的服务端口号，要保证与其他服务不冲突，如8080

我的配置如下：

spring.datasource.url=jdbc:mysql://127.0.0.1:3306/dbgirl?useUnicode=true&characterEncoding=UTF-8&serverTimezone=GMT
spring.datasource.username=root
spring.datasource.password=newpass
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver

mybatis.typeAliasesPackage=com.ljy.project.springdemo.domain
mybatis.mapperLocations=classpath:mapper/*.xml
logging.level.com.shizhao.project.springdemo:DEBUG
server.port=8080

5.启动程序，在浏览器地址栏输入http://localhost:8080/try/getAll，得到结果：

此处能看到返回值为json格式，是因为我使用了插件：

到此，创建springboot+mybatis且返回值带错误码的项目创建成功。

 

补充：

sql语句除了能通过注解写在UserDao中外，还能写在mapper.xml中。在resources文件夹下创建mapper文件夹，在mapper文件夹下创建UserMapper.xml文件：

    
        
        
        
    

    
        SELECT * FROM User
    

在UserDao中使用：

在UserController中直接调用：

在浏览器地址栏中输入http://localhost:8080/try/user,结果如下：

 完整版项目连接：https://download.csdn.net/download/skye_95/11120802

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