spring boot连接mysql数据库

秒速五厘米 2023-01-18 06:47 146阅读 0赞

#### 一、pom.xml添加依赖 ####

<dependency>
       <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-data-jpa</artifactId>
     </dependency>
     <dependency>
         <groupId>mysql</groupId>
         <artifactId>mysql-connector-java</artifactId>
     </dependency>

#### 二、application.properties添加数据库配置 ####

spring.datasource.url=jdbc:mysql://localhost:3306/spring_boot_db?serverTimezone=GMT%2B8
    spring.datasource.username=root
    spring.datasource.password=123456
    spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
    
    spring.jpa.properties.hibernate.hbm2ddl.auto=update
    spring.jpa.properties.hibernate.dialect=org.hibernate.dialect.MySQL5InnoDBDialect
    spring.jpa.show-sql= true

如果数据库连接写成spring.datasource.url=jdbc:mysql://localhost:3306/spring\_boot ，由于MySQL版本的问题，可能会有以下的错误，在后面加上“?serverTimezone=GMT%2B8”，设置下时区，解决。  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjYwMDM5OA_size_16_color_FFFFFF_t_70]  
设置驱动，spring.datasource.driver-class-name=com.mysql.jdbc.Driver会有下面红色的警告信息。说的是`com.mysql.jdbc.Driver'被弃用了，要使用新的驱动`com.mysql.cj.jdbc.Driver’，改成`com.mysql.cj.jdbc.Driver'以后一切正常。 Loading class`com.mysql.jdbc.Driver’. This is deprecated. The new driver class is \`com.mysql.cj.jdbc.Driver’. The driver is automatically registered via the SPI and manual loading of the driver class is generally unnecessary.  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjYwMDM5OA_size_16_color_FFFFFF_t_70 1]

#### 三、添加实体类 ####

@Entity代表这是一个实体类，@Table(name=”user”)用来对应数据库中的use表，@Id用来表达主键，@Column(name=”id”)表明一个id属性。

@GeneratedValue使主键自增，如果还有疑问，可参考@GeneratedValue源码解析。

package com.example.demo.domain;
    
    import java.io.Serializable;
    
    import javax.persistence.Column;
    import javax.persistence.Entity;
    import javax.persistence.GeneratedValue;
    import javax.persistence.Id;
    import javax.persistence.Table;
    
    @Entity
    @Table(name = "user")
    public class User implements Serializable { 
    
        private static final long serialVersionUID = 1L;
    
        @Id
        @GeneratedValue
        private Long id;
        @Column(name = "username")
        private String userName;
        @Column(name = "password")
        private String passWord;
    
        public User() { 
            super();
        }
    
        public User(String userName, String passWord) { 
            super();
            this.userName = userName;
            this.passWord = passWord;
        }
    
        public Long getId() { 
            return id;
        }
    
        public void setId(Long 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;
        }
    
    }

#### 四、添加Dao ####

Dao层主要用来实现对数据库的增、删、查、改。 dao只要继承JpaRepository类就可以，几乎可以不用写方法，可以根据方法名来自动的生产SQL，比如findByUserName 会自动生产一个以 userName 为参数的查询方法。

package com.example.demo.dao;
    
    import org.springframework.data.jpa.repository.JpaRepository;
    
    import com.example.demo.domain.User;
    
    public interface UserRepository extends JpaRepository<User, Long> { 
    
        User findByUserName(String userName);
    
    }

#### 五、添加Controller ####

package com.example.demo.controller;
    
    import java.util.ArrayList;
    import java.util.List;
    
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.bind.annotation.ResponseBody;
    import org.springframework.web.bind.annotation.RestController;
    
    import com.example.demo.dao.UserRepository;
    import com.example.demo.domain.User;
    
    @RestController
    @RequestMapping("user")
    public class UserController { 
    
        @Autowired
        private UserRepository userRepository;
    
        @RequestMapping("/getAllUser")
        @ResponseBody
        public List<User> findAll() { 
            List<User> list = new ArrayList<User>();
            list = userRepository.findAll();
            return list;
        }
    
        @RequestMapping("/getByUserName")
        @ResponseBody
        public User getByUserName(String userName) { 
            User user = userRepository.findByUserName(userName);
            return user;
        }
    
    }

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjYwMDM5OA_size_16_color_FFFFFF_t_70]: /images/20221021/d989e2a0be9d480d9e7e0219c3e880e0.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjYwMDM5OA_size_16_color_FFFFFF_t_70 1]: /images/20221021/a1a1a484260642179186e5bf7e9409f6.png