spring boot 项目连接数据库查询数据过程

爱被打了一巴掌 2022-12-08 04:42 114阅读 0赞

首先你要有一个spring boot的web项目，只是项目的目录

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## 一、配置pom.xml文件 ##

<?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>
    
        <parent>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-parent</artifactId>
            <version>2.3.3.RELEASE</version>
            <relativePath/> 
        </parent>
    
        <groupId>com.ts</groupId>
        <artifactId>industry</artifactId>
        <version>1.0-SNAPSHOT</version>
    
        <dependencies>
            
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-jdbc</artifactId>
            </dependency>
            
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-web</artifactId>
            </dependency>
            
            <dependency>
                <groupId>org.mybatis.spring.boot</groupId>
                <artifactId>mybatis-spring-boot-starter</artifactId>
                <version>2.1.3</version>
            </dependency>
            
            <dependency>
                <groupId>mysql</groupId>
                <artifactId>mysql-connector-java</artifactId>
                <scope>runtime</scope>
            </dependency>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-test</artifactId>
                <scope>test</scope>
                <exclusions>
                    <exclusion>
                        <groupId>org.junit.vintage</groupId>
                        <artifactId>junit-vintage-engine</artifactId>
                    </exclusion>
                </exclusions>
            </dependency>
        </dependencies>
    
        
        <build>
            <plugins>
                <plugin>
                    <groupId>org.springframework.boot</groupId>
                    <artifactId>spring-boot-maven-plugin</artifactId>
                </plugin>
            </plugins>
    
            <resources>
                
                <resource>
                    <directory>src/main/java</directory>
                    <includes>
                        <include>**/*.xml</include>
                    </includes>
                </resource>
    
                
    
    
    
            </resources>
        </build>
        
    </project>

## 二、配置application文件 ##

这里我的格式为yml ，application.yml

其中 URL 后面跟换成你自己的地址，还有 serverTimezone=GMT 这个一定要配置

不然会报错：

java.sql.SQLException: The server time zone value '�й���׼ʱ��' 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.

还有 driverClassName 后面 有点是 com.mysql.jdbc.Driver 这要看你使用的版本。

报错：Loading class \`com.mysql.jdbc.Driver'. This is deprecated. The new driver class is \`com.mysql.cj.jdbc.Driver'.

server:
      port: 8080
    spring:
      datasource:
        url: jdbc:mysql://localhost:3306/industry?serverTimezone=GMT&useUnicode=true&characterEncoding=UTF-8&useSSL=false 
    #你学习mybatis时，使用的数据库地址
        driverClassName: com.mysql.cj.jdbc.Driver
        username: root
        password: root
    mybatis:
      type-aliases-package: com.ts.pojo
      mapper-locations: com/ts/mapper/*.xml

## 三、配置mapper.xml 、mapper和有实体类 ##

<?xml version="1.0" encoding="UTF-8" ?>
    <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd" >
    <mapper namespace="com.ts.mapper.UserMapper">
    
        <select id="test" resultType="com.ts.pojo.User">
            select * from s_user;
        </select>
    
    </mapper>

package com.ts.mapper;
    
    import com.ts.pojo.User;
    import org.apache.ibatis.annotations.Mapper;
    import org.springframework.stereotype.Component;
    
    import java.util.List;
    
    @Mapper
    @Component     //加上后再注入时不会爆红
    public interface UserMapper {
    
        List<User> test();
    
    }

实体类我就不写了。》》》》

## 四、service ##

package com.ts.serviceimpl;
    
    import com.ts.mapper.UserMapper;
    import com.ts.pojo.User;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.stereotype.Service;
    
    import java.util.List;
    
    @Service
    public class UserService {
    
        @Autowired
        private UserMapper userMapper;
    
    
        public List<User> test() {
            List<User> test = userMapper.test();
            return test;
        }
    
    }

## 五、Controlle ##

package com.ts.controller;
    
    import com.ts.pojo.User;
    import com.ts.service.UserService;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.web.bind.annotation.*;
    
    import java.util.List;
    
    @RestController
    @RequestMapping("user")
    public class UserController {
    
        @Autowired
        private UserService userService;
    
        /**
         * 测试数据
         * @return
         */
        @GetMapping("test")
        @ResponseBody
        public List<User> test(){
            List<User> list = userService.test();
            return list;
        }
    }

## 六、运行测试 ##

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