【轉】Spring Boot實戰(二):Spring Boot連線MySQL資料庫
1. pom.xml新增依賴
<dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-data-jpa</artifactId> </dependency> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> </dependency>
2. application.properties新增資料庫配置
spring.datasource.url=jdbc:mysql://localhost:3306/spring_boot?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
如果資料庫連線寫成spring.datasource.url=jdbc:mysql://localhost:3306/spring_boot ,由於MySQL版本的問題,可能會有以下的錯誤,在後面加上“?serverTimezone=GMT%2B8”,設定下時區,解決。
設定驅動,spring.datasource.driver-class-name=com.mysql.jdbc.Driver會有下面紅色的警告資訊。說的是com.mysql.jdbc.Driver
com.mysql.cj.jdbc.Driver1
,改成com.mysql.cj.jdbc.Driver
以後一切正常。
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.
3. 新增實體類
@Entity代表這是一個實體類,@Table(name=”user”)用來對應資料庫中的use表,@Id用來表達主鍵,@Column(name=”id”)表明一個id屬性。
@GeneratedValue使主鍵自增,如果還有疑問,可參考@GeneratedValue原始碼解析。
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; } }
4. 新增Dao
Dao層主要用來實現對資料庫的增、刪、查、改。 dao只要繼承JpaRepository類就可以,幾乎可以不用寫方法,可以根據方法名來自動的生產SQL,比如findByUserName 會自動生產一個以 userName 為引數的查詢方法。
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); }
5. 新增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; } }
工程新增檔案後工程結構圖:
6. 新建資料庫
新建資料庫mysql://localhost:3306/spring_boot ,必須的一個步驟。hibernate雖然會自動新建表,但是資料庫還是要手動建好的。
使用Navicat新建本地資料庫,連線名上面右鍵- >新建資料庫 ->填寫資料庫資訊 - > 確定。
在user表中,插入兩條測試資料:
7. 測試
啟動專案。用Postman傳送請求進行測試: