添加依賴

<dependencies><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-data-jpa</artifactId></dependency><dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><scope>runtime</scope></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-thymeleaf</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency></dependencies>

實體類

package cn.clboy.springbootjpa.entity;import javax.persistence.*;@Entity //使用JPA注解配置映射關系,告訴JPA這是一個實體類（和數據表映射的類）
@Table(name = "tbl_user")   //@Table來指定和哪個數據表對應;如果省略默認表名類名小寫；
public class User {@Id //這是一個主鍵@GeneratedValue(strategy = GenerationType.IDENTITY) //自增主鍵private Integer id;@Column(name = "last_name",length = 50) //這是和數據表對應的一個列private String lastName;@Column //省略默認列名就是屬性名private String email;public Integer getId() {return id;}public void setId(Integer id) {this.id = id;}public String getLastName() {return lastName;}public void setLastName(String lastName) {this.lastName = lastName;}public String getEmail() {return email;}public void setEmail(String email) {this.email = email;}
}

DAO

package cn.clboy.springbootjpa.repository;import cn.clboy.springbootjpa.entity.User;
import org.springframework.data.jpa.repository.JpaRepository;/*** 繼承JpaRepository來完成對數據庫的操作* 泛型是（實體類，主鍵）*/
public interface UserRepository extends JpaRepository<User, Integer> {}

配置文件

spring:datasource:username: rootpassword: 123456url: jdbc:mysql://localhost:3306/jdbc?useUnicode=true&characterEncoding=utf-8&serverTimezone=GMT%2B8type: com.alibaba.druid.pool.DruidDataSourcedriver-class-name: com.mysql.cj.jdbc.DriverinitialSize: 5minIdle: 5maxActive: 20maxWait: 60000timeBetweenEvictionRunsMillis: 60000minEvictableIdleTimeMillis: 300000validationQuery: SELECT 1 FROM DUALtestWhileIdle: truetestOnBorrow: falsetestOnReturn: falsepoolPreparedStatements: true#   配置監控統計攔截的filters，去掉后監控界面sql無法統計，'wall'用于防火墻filters: stat,wallmaxPoolPreparedStatementPerConnectionSize: 20useGlobalDataSourceStat: trueconnectionProperties: druid.stat.mergeSql=true;druid.stat.slowSqlMillis=500

添加用戶

• http://localhost:8080/user?lastName=zhangsan&email=123456@qq.com
• http://localhost:8080/user?lastName=lisi&email=78215646@qq.com
• http://localhost:8080/user/1，拋出500錯誤，原因是getOne方法使用的懶加載，獲取到的只是代理對象，轉換為json時會報錯

解決懶加載

1. 關閉懶加載，在實體類上加上@Proxy（lazy = false）注解

   @Entity
   @Table(name = "tbl_user")
   @Proxy(lazy = false)
   public class User
   

2. 轉Json的時候忽略hibernateLazyInitializer和handler屬性

   @Entity
   @Table(name = "tbl_user")
   @JsonIgnoreProperties(value = {"hibernateLazyInitializer", "handler"})
   public class User 

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