springboot-jpa的实现操作

JPA全称为Java Persistence API（Java持久层API），它是Sun公司在JavaEE 5中提出的Java持久化规范。

它为Java开发人员提供了一种对象/关联映射工具，来管理Java应用中的关系数据，JPA吸取了目前Java持久化技术的优点，旨在规范、简化Java对象的持久化工作。

JPA对于单表的或者简单的SQL查询非常友好，甚至可以说非常智能。他为你准备好了大量的拿来即用的持久层操作方法。甚至只要写findByName这样一个接口方法，他就能智能的帮你执行根据名称查找实体类对应的表数据，完全不用写SQL。

它相对于mybatis来说不用写xml等配置，简直方便的不行，对于我们开发者来说，谁更简单，开发效率更高，我们就喜欢谁(不喜欢不行，看看产品经理手里的菜刀)！！！

这时候mybatis就不服了，我确实需要写一大堆乱七八糟的xml，但是也可以用注解啊。

还不是要写sql，总是一写增删改查sql，有没有把这些常见的增删改查全部封装起来，我们直接调用api，sql让它们自动组装就好了，说实话我自己封装了一个基于mybatis的组件，常见的增删改查，自己组装成sql去查询，后来由于没有oracle，sqlserver的数据库环境，对这些数据库的时间等等函数支持不好，又有jpa和mybatisplus这些现有的，我也就偷懒了

好了我们之前有实现过springboot-mybatis

springboot-mybatisplus的整合，现在就来实现一下jpa的，你们看看哪个比较方便好用，可以自己用用看

这是我实现的demo预览

由于我想看到效果，又不想装postman来测试，我就集成了swagger

最终效果如上图

好了，我直接放代码了

<? xml version = "1.0" encoding = "UTF-8" ?> <project xmlns = "http://maven.apache.org/POM/4.0.0" xmlns:xsi = "http://HdhCmsTestw3.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>   <groupId> com.zkb </groupId> <artifactId> spring-data-jpa </artifactId> <version> 1.0-SNAPSHOT </version> <build> <plugins> <plugin> <groupId> org.apache.maven.plugins </groupId> <artifactId> maven-compiler-plugin </artifactId> <configuration> <source> 8 </source> <target> 8 </target> </configuration> </plugin> </plugins> </build> <dependencies> <dependency> <groupId> org.springframework.boot </groupId> <artifactId> spring-boot-starter-web </artifactId> <version> 2.1.1.RELEASE </version> </dependency>   <dependency> <groupId> org.springframework.boot </groupId> <artifactId> spring-boot-starter-data-jpa </artifactId> <version> 2.1.1.RELEASE </version> </dependency>   <dependency> <groupId> mysql </groupId> <artifactId> mysql-connector-java </artifactId> <version> 8.0.18 </version> </dependency>   <dependency> <groupId> org.projectlombok </groupId> <artifactId> lombok </artifactId> <version> 1.18.12 </version> </dependency>   <dependency> <groupId> org.springframework.boot </groupId> <artifactId> spring-boot-devtools </artifactId> <version> 2.0.4.RELEASE </version> </dependency>   <dependency> <groupId> org.springframework.boot </groupId> <artifactId> spring-boot-starter-test </artifactId> <version> 2.1.2.RELEASE </version> <scope> test </scope> </dependency> <dependency> <groupId> com.alibaba </groupId> <artifactId> druid </artifactId> <version> 1.0.31 </version> </dependency> <dependency> <groupId> org.junit.jupiter </groupId> <artifactId> junit-jupiter </artifactId> <version> RELEASE </version> <scope> compile </scope> </dependency> <dependency> <groupId> org.junit.jupiter </groupId> <artifactId> junit-jupiter </artifactId> <version> RELEASE </version> <scope> compile </scope> </dependency>   <dependency> <groupId> org.slf4j </groupId> <artifactId> slf4j-api </artifactId> <version> 1.7.25 </version> </dependency> <dependency> <groupId> org.springframework.boot </groupId> <artifactId> spring-boot-test </artifactId> <version> 2.2.2.RELEASE </version> <scope> compile </scope> </dependency>   <dependency> <groupId> io.springfox </groupId> <artifactId> springfox-swagger2 </artifactId> <version> 2.9.2 </version> <exclusions> <exclusion> <groupId> io.swagger </groupId> <artifactId> swagger-annotations </artifactId> </exclusion> <exclusion> <groupId> io.swagger </groupId> <artifactId> swagger-models </artifactId> </exclusion> </exclusions> </dependency> <dependency> <groupId> io.swagger </groupId> <artifactId> swagger-annotations </artifactId> <version> 1.5.22 </version> </dependency>   <dependency> <groupId> io.swagger </groupId> <artifactId> swagger-models </artifactId> <version> 1.5.22 </version> </dependency> <!-- swagger-ui --> <dependency> <groupId> io.springfox </groupId> <artifactId> springfox-swagger-ui </artifactId> <version> 2.9.2 </version> </dependency>   <dependency> <groupId> com.github.xiaoymin </groupId> <artifactId> swagger-bootstrap-ui </artifactId> <version> 1.9.1 </version> </dependency> </dependencies>   </project> server : port : 5001 spring : datasource : type : com . alibaba . druid . pool . DruidDataSource #Druid 是阿里巴巴开源平台上一个数据库连接池实现，结合了 C3P0、DBCP、PROXOOL 等 DB 池的优点，同时加入了日志监控 driver - class - name : com . mysql . cj . jdbc . Driver url : jdbc : mysql : //localhost:3306/test-demo?useUnicode=true&characterEncoding=utf-8&useSSL=false&serverTimezone=UTC&autoReconnect=true&failOverReadOnly=false&zeroDateTimeBehavior=convertToNull username : root password : root dbcp2 : min - idle : 5 initial - size : 5 max - total : 5 max - wait - millis : 200 jpa : database : mysql database - platform : org . hibernate . dialect . MySQL5InnoDBDialect show - sql : true hibernate : ddl - auto : update package com . zkb . entity ; import com . fasterxml . jackson . databind . annotation . JsonSerialize ; import com . fasterxml . jackson . databind . ser . std . ToStringSerializer ; import io . swagger . annotations . ApiModel ; import io . swagger . annotations . ApiModelProperty ; import lombok . Data ; import javax . persistence .*; /** * 实体类 */ @Entity @Table ( name = "t_user" ) @Data @ApiModel ( value = "用户信息" , description = "用户信息" ) public class User { @Id @GeneratedValue ( strategy = GenerationType . IDENTITY ) @ApiModelProperty ( value = "主键" ) @JsonSerialize ( using = ToStringSerializer . class ) private Long id ;   @Column ( name = "username" ) @ApiModelProperty ( value = "用户名" ) private String username ;   @Column ( name = "password" ) @ApiModelProperty ( value = "密码" ) private String password ;   } package com . zkb . dao ; import com . zkb . entity . User ; import org . springframework . data . jpa . repository . JpaRepository ; public interface UserRepository extends JpaRepository < User , Long > { } package com . zkb . service ; import com . zkb . entity . User ; import java . util . List ; public interface UserService { public void deleteUser ( Long id ); List < User > getList (); } package com . zkb . service . impl ; import com . zkb . dao . UserRepository ; import com . zkb . entity . User ; import com . zkb . service . UserService ; import org . springframework . beans . factory . annotation . Autowired ; import org . springframework . stereotype . Service ; import java . util . List ; @Service public class UserServiceImpl implements UserService {   @Autowired private UserRepository userRepository ;   @Override public void deleteUser ( Long id ) { System . out . println ( userRepository ); userRepository . deleteById ( id ); }   @Override public List < User > getList () { return userRepository . findAll (); } } package com . zkb . controller ; import com . zkb . entity . User ; import com . zkb . service . UserService ; import io . swagger . annotations . Api ; import io . swagger . annotations . ApiOperation ; import org . springframework . beans . factory . annotation . Autowired ; import org . springframework . web . bind . annotation . PostMapping ; import org . springframework . web . bind . annotation . RequestMapping ; import org . springframework . web . bind . annotation . RequestParam ; import org . springframework . web . bind . annotation . RestController ; import java . util . List ; @RestController @RequestMapping ( "/user" ) @Api ( value = "user" , tags = "user" ) public class UserController {   @Autowired private UserService userService ;   @PostMapping ( "/del" ) @ApiOperation ( value = "删除" , notes = "删除" ) public String delete ( @RequestParam ( "id" ) Long id ){ userService . deleteUser ( id ); return "true" ; }   @PostMapping ( "/getList" ) @ApiOperation ( value = "查询所有" , notes = "查询所有" ) public List < User > getList (){ return userService . getList (); } } package com . zkb . conf ; import io . swagger . annotations . ApiOperation ; import io . swagger . models . auth . In ; import org . springframework . context . annotation . Bean ; import org . springframework . context . annotation . Configuration ; import springfox . documentation . builders . ApiInfoBuilder ; import springfox . documentation . builders . PathSelectors ; import springfox . documentation . builders . RequestHandlerSelectors ; import springfox . documentation . service . ApiInfo ; import springfox . documentation . service . ApiKey ; import springfox . documentation . service . Contact ; import springfox . documentation . spi . DocumentationType ; import springfox . documentation . spring . web . plugins . Docket ; import springfox . documentation . swagger2 . annotations . EnableSwagger2 ; import java . util . Arrays ; import java . util . List ; @Configuration @EnableSwagger2 public class SwaggerApp { @Bean public Docket createRestApi1 () { return new Docket ( DocumentationType . SWAGGER_2 ). enable ( true ). apiInfo ( apiInfo ()). select () . apis ( RequestHandlerSelectors . withMethodAnnotation ( ApiOperation . class )) . apis ( RequestHandlerSelectors . basePackage ( "com.zkb.controller" )) . paths ( PathSelectors . any ()). build (). securitySchemes ( apiKeyList ()). groupName ( "接口中心" ); }   private ApiInfo apiInfo () { return new ApiInfoBuilder () . title ( "API" ) . contact ( new Contact ( "XXXXX" , "http://XXXXXX.XXXX/" , "" )) . version ( "1.0" ) . description ( "API 描述" ) . build (); }   private List < ApiKey > apiKeyList () { return Arrays . asList ( new ApiKey ( "登录token" , "token" , In . HEADER . name ()), new ApiKey ( "设备类型(android,ios,pc)---必填" , "deviceType" , In . HEADER . name ())); } } package com . zkb ; import org . springframework . boot . SpringApplication ; import org . springframework . boot . autoconfigure . SpringBootApplication ; import springfox . documentation . swagger2 . annotations . EnableSwagger2 ; @SpringBootApplication @EnableSwagger2 public class App { public static void main ( String [] args ) { SpringApplication . run ( App . class , args ); } } CREATE TABLE `t_user` ( `id` bigint NOT NULL AUTO_INCREMENT , `username` varchar ( 50 ) COLLATE utf8mb4_general_ci DEFAULT NULL , `password` varchar ( 50 ) COLLATE utf8mb4_general_ci DEFAULT NULL , PRIMARY KEY ( `id` ) USING BTREE ) ENGINE = InnoDB AUTO_INCREMENT = 1214893367637352451 DEFAULT CHARSET = utf8mb4 COLLATE = utf8mb4_general_ci ;

非常简单的一张表，注意数据库名称

到这里就已经实现了一个非常简单的jpa demo了

当然我这里只是指路，让知怎么用

补充：SpringBoot使用JPA实现增删查改

一、运行环境

SpringBoot2.3.0

JDK1.8

IDEA2020.1.2

MySQL5.7

二、依赖及应用程序配置

<dependency> <groupId> org.springframework.boot </groupId> <artifactId> spring-boot-starter-data-jpa </artifactId> </dependency> <dependency> <groupId> org.springframework.boot </groupId> <artifactId> spring-boot-starter-thymeleaf </artifactId> </dependency> <dependency> <groupId> org.springframework.boot </groupId> <artifactId> spring-boot-starter-validation </artifactId> </dependency> <dependency> <groupId> org.springframework.boot </groupId> <artifactId> spring-boot-starter-web </artifactId> </dependency> <dependency> <groupId> mysql </groupId> <artifactId> mysql-connector-java </artifactId> <scope> runtime </scope> </dependency> <dependency> <groupId> org.projectlombok </groupId> <artifactId> lombok </artifactId> <optional> true </optional> </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>

1、升级到SpringBoot2.2，spring-boot-starter-test默认使用JUnit 5作为单元测试框架 ，写单元测试时注解@RunWith(Spring.class)升级为@ExtendWith(SpringExtension.class)

2、升级到SpringBoot2.3，hibernate-validator从spring-boot-starter-web移除，需要单独引入

3、升级到SpringBoot2.3，MySQL驱动由com.mysql.jdbc.Driver变更为com.mysql.cj.jdbc.Driver;同时，数据源url需要添加serverTimezone=UTC&useSSL=false参数

3、升级到SpringBoot2.x，默认不自动注入HiddenHttpMethodFilter，需要设置spring.mvc.hiddenmethod.filter.enabled=true开启PUT、DELETE方法支持

应用程序配置如下：

spring . application . name = springbootjpa management . endpoints . jmx . exposure . include =* management . endpoints . web . exposure . include =* management . endpoint . health . show - details = always # 应用服务 WEB 访问端口 server . port = 8080 # Actuator Web 访问端口 management . server . port = 8081 # mysql setting spring . datasource . driver - class - name = com . mysql . cj . jdbc . Driver spring . datasource . url = jdbc : mysql : //localhost:3306/springbootjpa?serverTimezone=UTC&useSSL=false spring . datasource . username = username spring . datasource . password = password # JPA setting spring . jpa . properties . hibernate . hbm2ddl . auto = update spring . jpa . properties . hibernate . dialect = org . hibernate . dialect . MySQL5InnoDBDialect spring . jpa . show - sql = true # thymeleaf setting spring . thymeleaf . cache = false # delete、put方法支持 spring . mvc . hiddenmethod . filter . enabled = true

三、定义实体

使用@Entity标记实体类

import lombok . Data ; import javax . persistence .*; import javax . validation . constraints . NotEmpty ; import java . io . Serializable ; @Entity @Data public class Article extends BaseEntity implements Serializable { @Id @GeneratedValue ( strategy = GenerationType . IDENTITY ) private Long id ; @Column ( nullable = false , unique = true ) @NotEmpty ( message = "标题不能为空" ) private String title ; @Column ( nullable = false ) private String body ; }

为了自动添加创建日期、修改日期、创建人及修改人，我们把创建、修改信息放到父类中由实体类继承，并开启SpringBoot的自动审计功能，将创建/修改信息自动注入

1、定义实体类的父类,@CreatedDate、@LastModifiedDate、@CreatedBy、@LastModifiedBy标注相应字段

import org . hibernate . annotations . Columns ; import org . springframework . data . annotation . CreatedBy ; import org . springframework . data . annotation . CreatedDate ; import org . springframework . data . annotation . LastModifiedBy ; import org . springframework . data . annotation . LastModifiedDate ; import org . springframework . data . jpa . domain . support . AuditingEntityListener ; import javax . persistence . Column ; import javax . persistence . EntityListeners ; import javax . persistence . MappedSuperclass ; @MappedSuperclass @EntityListeners ( AuditingEntityListener . class ) public class BaseEntity { @CreatedDate private Long createTime ; @LastModifiedDate private Long updateTime ;   @Column ( name = "create_by" ) @CreatedBy private String createBy ; @Column ( name = "lastmodified_by" ) @LastModifiedBy private String lastmodifiedBy ;   public Long getCreateTime () { return createTime ; } public void setCreateTime ( Long createTime ) { this . createTime = createTime ; } public Long getUpdateTime () { return updateTime ; } public void setUpdateTime ( Long updateTime ) { this . updateTime = updateTime ; }   public String getCreateBy () { return createBy ; } public void setCreateBy ( String createBy ) { this . createBy = createBy ; } public String getLastmodifiedBy () { return lastmodifiedBy ; } public void setLastmodifiedBy ( String lastmodifiedBy ) { this . lastmodifiedBy = lastmodifiedBy ; } }

@MappedSuperclass注解：

作用于实体类的父类上，父类不生成对应的数据库表

标注@MappedSuperclass的类不能再标注@Entity或@Table注解，也无需实现序列化接口

每个子类（实体类）对应一张数据库表，数据库表包含子类属性和父类属性

标注@MappedSuperclass的类可以直接标注@EntityListeners实体监听器

@EntityListeners(AuditingEntityListener.class)注解：

作用范围仅在标注@MappedSuperclass类的所有继承类中，并且实体监听器可以被其子类继承或重载

开启JPA的审计功能，需要在SpringBoot的入口类标注@EnableJpaAuditing

创建日期、修改日期有默认方法注入值，但创建人和修改人注入则需要手动实现AuditorAware接口:

@Configuration public class BaseEntityAuditor implements AuditorAware < String > { @Override public Optional < String > getCurrentAuditor () { return "" ; } }

四、DAO层实现

JPA支持通过约定方法名进行数据库查询、修改：

import org . springframework . data . jpa . repository . JpaRepository ; import springbootjpa . entity . Article ; public interface ArticleRepository extends JpaRepository < Article , Long > { Article findById ( long id ); }

通过约定方法名查询，只需实现JpaRepository接口声明查询方法而不需要具体实现

此外，可以在方法上标注@Query实现JPQL或原生SQL查询

JpaRepository<T, ID>,T表示要操作的实体对象，ID表示主键。该接口继承了分页排序接口PadingAndSortRepository,通过构建Pageable实现分页查询：

@Autowired private ArticleRepository articleRepository ; @RequestMapping ( "" ) public ModelAndView articlelist ( @RequestParam ( value = "start" , defaultValue = "0" ) Integer start , @RequestParam ( value = "limit" , defaultValue = "5" ) Integer limit ) { start = start < 0 ? 0 : start ; Sort sort = Sort . by ( Sort . Direction . DESC , "id" ); Pageable pageable = PageRequest . of ( start , limit , sort ); Page < Article > page = articleRepository . findAll ( pageable ); ModelAndView modelAndView = new ModelAndView ( "article/list" ); modelAndView . addObject ( "page" , page ); return modelAndView ; }

如果根据某一字段排序，可以用Sort.by方法构建Sort对象；如果根据多个字段排序，首先构建Sort.Order数组List<Sort.Order>,然后再传入Sort.by方法构建Sort对象。

PageRequest.of方法生成Pageable对象

五、Contrller 控制器

import org . springframework . beans . factory . annotation . Autowired ; import org . springframework . data . domain . Page ; import org . springframework . data . domain . PageRequest ; import org . springframework . data . domain . Pageable ; import org . springframework . data . domain . Sort ; import org . springframework . stereotype . Controller ; import org . springframework . web . bind . annotation .*; import org . springframework . web . servlet . ModelAndView ; import springbootjpa . entity . Article ; import springbootjpa . repository . ArticleRepository ; @Controller @RequestMapping ( "/article" ) public class ArticleController { @Autowired private ArticleRepository articleRepository ; @RequestMapping ( "" ) public ModelAndView articlelist ( @RequestParam ( value = "start" , defaultValue = "0" ) Integer start , @RequestParam ( value = "limit" , defaultValue = "5" ) Integer limit ) { start = start < 0 ? 0 : start ; Sort sort = Sort . by ( Sort . Direction . DESC , "id" ); Pageable pageable = PageRequest . of ( start , limit , sort ); Page < Article > page = articleRepository . findAll ( pageable ); ModelAndView modelAndView = new ModelAndView ( "article/list" ); modelAndView . addObject ( "page" , page ); return modelAndView ; } @RequestMapping ( "/add" ) public String addArticle () { return "article/add" ; } @PostMapping ( "" ) public String saveArticle ( Article article ) { articleRepository . save ( article ); return "redirect:/article" ; } @GetMapping ( "/{id}" ) public ModelAndView getArticle ( @PathVariable ( "id" ) Integer id ) { Article article = articleRepository . findById ( id ); ModelAndView modelAndView = new ModelAndView ( "article/show" ); modelAndView . addObject ( "article" , article ); return modelAndView ; } @DeleteMapping ( "/{id}" ) public String deleteArticle ( @PathVariable ( "id" ) long id ) { System . out . println ( "put 方法" ); articleRepository . deleteById ( id ); return "redirect:/article" ; } @GetMapping ( "edit/{id}" ) public ModelAndView editArticle ( @PathVariable ( "id" ) Integer id ) { Article article = articleRepository . findById ( id ); ModelAndView modelAndView = new ModelAndView ( "article/edit" ); modelAndView . addObject ( "article" , article ); return modelAndView ; } @PutMapping ( "/{id}" ) public String editArticleSave ( Article article , long id ) { System . out . println ( "put 方法" ); article . setId ( id ); articleRepository . save ( article ); return "redirect:/article" ; } }

因为<form>表单只能发送GET或POST请求，spring3引入一个监听器HiddenHttpMethodFilter来将POST请求转换为PUT或POST请求。

SpringBoot2.x开始默认不自动注入HiddenHttpMethodFilter，需要设置spring.mvc.hiddenmethod.filter.enabled=true开启PUT、DELETE方法支持

配置完后，前端页面需要在表单中加入隐藏域，表明实际请求方法：

<!-- DELETE 请求 --> <form id = "deletePost" method = "POST" action = "" > <input type = "hidden" name = "_method" value = "delete" > </form> <!-- PUT 请求 --> <form id = "putPost" method = "POST" action = "" > <input type = "hidden" name = "_method" value = "put" > </form>

六、其他

th:value和th:field区别：

th:value解析成html，表现为：value="${th:value}"

th:field解析成html，表现为：name="${th:name}" value="${th:value}"

以上为个人经验，希望能给大家一个参考，也希望大家多多支持我们。如有错误或未考虑完全的地方，望不吝赐教。

原文链接：https://blog.csdn.net/qq_14926283/article/details/110633636

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