SpringBoot入门之基于注解的Mybatis

今天学习下SpringBoot集成mybatis,集成mybatis一般有两种方式，一个是基于注解的一个是基于xml配置的。今天先了解下基于注解的mybatis集成。

一、引入依赖项

因为是mybatis嘛,肯定是要有mybatis相关的,同时用的是mysql,所以也需要引入mysql相关的。

        <!-- https://mvnrepository.com/artifact/org.mybatis.spring.boot/mybatis-spring-boot-starter -->
        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
            <version>1.3.2</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.11</version>
        </dependency>

二、创建model

这里创建了一个User的model,这样方便与数据库的表对照，这里在mysql中创建了一个名为mybatis的数据库,里面创建了一个user的表.同时创建了枚举类UserSexEnum.

CREATE TABLE `user` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(20) DEFAULT NULL,
  `age` int(11) DEFAULT NULL,
  `sex` varchar(20) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=9 DEFAULT CHARSET=utf8;

package com.example.model;

import java.io.Serializable;

public class User implements Serializable{
    @Override
    public String toString() {
        // TODO Auto-generated method stub
        return  "User [id=" + Id + ", name=" + Name + ", age=" + Age + "]";

    }

    public int getId() {
        return Id;
    }
    public void setId(int id) {
        Id = id;
    }
    public String getName() {
        return Name;
    }
    public void setName(String name) {
        Name = name;
    }
    public int getAge() {
        return Age;
    }
    public void setAge(int age) {
        Age = age;
    }
    private int Id;
    private String Name;
    private int Age; 
    
    private UserSexEnum Sex;

    public UserSexEnum getSex() {
        return Sex;
    }
    public void setSex(UserSexEnum sex) {
        Sex = sex;
    }


}

package com.example.model;

public enum UserSexEnum {
    MAN, WOMAN
}

三、创建Mapper

这里需要把model与操作数据库的sql对照起来，用什么对照呢?那就需要创建一个mapper.这里有增删改查。

package com.example.mapper;
import java.util.List;

import org.apache.ibatis.annotations.Delete;
import org.apache.ibatis.annotations.Insert;
import org.apache.ibatis.annotations.Result;
import org.apache.ibatis.annotations.Results;
import org.apache.ibatis.annotations.Select;
import org.apache.ibatis.annotations.Update;

import com.example.model.*;;

public interface  UserMapper {

    @Select("SELECT * FROM user")

    @Results({

        @Result(property = "Sex",  column = "sex", javaType = UserSexEnum.class),

        @Result(property = "Name", column = "name")

    })

    List<User> getAll();

    

    @Select("SELECT * FROM user WHERE id = #{id}")

    @Results({

        @Result(property = "Sex",  column = "sex", javaType = UserSexEnum.class),

        @Result(property = "Name", column = "name")

    })

    User getOne(int id);



    @Insert("INSERT INTO user(name,age,sex) VALUES(#{name}, #{age}, #{sex})")

    void insert(User user);



    @Update("UPDATE user SET name=#{userName},age=#{age} WHERE id =#{id}")

    void update(User user);



    @Delete("DELETE FROM user WHERE id =#{id}")

    void delete(int id);
}

四、配置扫描

上面配置了mapper,那怎么让系统知道mapper放在哪里呢?于是有了@MapperScan注解。

package com.example.demo;

import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
@MapperScan("com.example.mapper")
public class DemoApplication {

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

五、创建Controller

这里创建了UserController,一个是显示所有用户,一个是新增一个用户之后再显示所有用户。

package com.example.demo;

import java.util.List;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;

import com.example.mapper.UserMapper;
import com.example.model.User;
import com.example.model.UserSexEnum;

@Controller
@RequestMapping("/user")
public class UserController {
    
    @Autowired
    private UserMapper userMapper;
    
    @RequestMapping(value = "/alluser.do",method = RequestMethod.GET)
    public String getallusers(Model model) {
       List<User> users=userMapper.getAll();
       model.addAttribute("users", users);
       return "userlist";
    }
    @RequestMapping(value = "/insert.do",method = RequestMethod.GET)
    public String adduser(Model model) {
       User user=new User();
       user.setName("cuiyw");
       user.setAge(27);
       user.setSex(UserSexEnum.MAN);
                
       userMapper.insert(user);
       List<User> users=userMapper.getAll();
       model.addAttribute("users", users);
       return "userlist";
    }
}

六、数据库配置

上面mapper也设置了,model也设置了,那要与数据库交互，肯定要配置数据库地址这些信息吧。这里在运行的时候还报了一个错误.nested exception is java.sql.SQLException: The server time zone value 'Öйú±ê׼ʱ¼ä' is unrecognized or represents more than one time zone. You must configure either the server or JDBC driver (via the serverTimezone configuration property) to use a more specifc time zone value if you want to utilize time zone support.在mysql中设置了下时区:set global time_zone='+8:00';

spring.mvc.view.prefix=/view/

spring.mvc.view.suffix=.jsp
mybatis.type-aliases-package=com.example.model

spring.datasource.driverClassName = com.mysql.cj.jdbc.Driver
spring.datasource.url = jdbc:mysql://localhost:3306/mybatis
spring.datasource.username = root
spring.datasource.password = 123456

七、创建页面显示

这里还是按照上一博客用jsp显示数据。

<%@ page language="java" contentType="text/html; charset=utf-8"
    pageEncoding="utf-8"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Insert title here</title>
</head>
<body>
    <table>
    <tr><th>名字</th><th>年龄</th><th>性别</th></tr>
    <c:forEach items="${users}" var="item">
            <tr><td>${item.name}</td><td>${item.age}</td><td>${item.sex}</td></tr>
        </c:forEach>
     </table>
</body>
</html>

 八、测试

这里先在浏览器打开http://localhost:8080/user/alluser.do，可以看到用户列表,然后输入http://localhost:8080/user/insert.do，就会看到列表显示多了一行数据。

九、小结

使用基于注解的集成mybatis比较省事方便，但有利有弊，对于多表相连的可能就不太方便，使用基于xml配置的可能就更会好些。