原文： https://howtodoinjava.com/spring-restful/spring-rest-crud-jpa-example/

学习使用 Spring REST 和 JPA 配置（以 H2 数据库为后端）创建 REST API 以进行分类操作，而无需 Spring boot 自动配置功能。

1. Maven 依赖

在此示例中，我们使用以下模块及其依赖项。

  • spring-webmvc – 用于处理请求
  • spring-data-jpa – 为接口提供了支持针对后端数据存储读取，更新，删除和创建记录的方法。
  • persistence-api – JPA 规范
  • javax.persistence -JPA 实现
  • Hibernate 实体管理器 – 作为实体供体商
  • Jackson – 用于 JSON 支持
  • H2 – 作为数据库

pom.xml

  1. <project xmlns="http://maven.apache.org/POM/4.0.0"
  2.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  3.     xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  4.     <modelVersion>4.0.0</modelVersion>
  6.     <groupId>com.howtodoinjava.rest</groupId>
  7.     <artifactId>SpringRestExample</artifactId>
  8.     <version>0.0.1-SNAPSHOT</version>
  9.     <packaging>war</packaging>
  11.     <name>SpringRestExample</name>
  12.     <url>http://maven.apache.org</url>
  14.     <properties>
  15.         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
  16.         <spring.version>5.1.6.RELEASE</spring.version>
  17.         <maven.compiler.source>1.8</maven.compiler.source>
  18.         <maven.compiler.target>1.8</maven.compiler.target>
  19.     </properties>
  21.     <dependencies>
  22.         <!-- spring webmvc -->
  23.         <dependency>
  24.             <groupId>org.springframework</groupId>
  25.             <artifactId>spring-webmvc</artifactId>
  26.             <version>${spring.version}</version>
  27.         </dependency>
  29.         <!-- spring data jpa -->
  30.         <dependency>
  31.             <groupId>org.springframework.data</groupId>
  32.             <artifactId>spring-data-jpa</artifactId>
  33.             <version>2.1.6.RELEASE</version>
  34.         </dependency>
  36.         <!-- persistence api -->
  37.         <dependency>
  38.             <groupId>javax.persistence</groupId>
  39.             <artifactId>persistence-api</artifactId>
  40.             <version>1.0.2</version>
  41.         </dependency>
  43.         <!-- persistence implementation -->
  44.         <dependency>
  45.             <groupId>org.eclipse.persistence</groupId>
  46.             <artifactId>javax.persistence</artifactId>
  47.             <version>2.1.0</version>
  48.         </dependency>
  50.         <!-- entity manager provider -->
  51.         <dependency>
  52.             <groupId>org.hibernate</groupId>
  53.             <artifactId>hibernate-entitymanager</artifactId>
  54.             <version>5.4.2.Final</version>
  55.         </dependency>
  57.         <!-- H2 database -->
  58.         <dependency>
  59.             <groupId>com.h2database</groupId>
  60.             <artifactId>h2</artifactId>
  61.             <version>1.4.199</version> 
  62.         </dependency>
  64.         <!-- JSON support -->
  65.         <dependency>
  66.             <groupId>com.fasterxml.jackson.core</groupId>
  67.             <artifactId>jackson-databind</artifactId>
  68.             <version>2.9.8</version>
  69.         </dependency>
  70.     </dependencies>
  71. </project>

2. DispatcherServlet声明

我们已经在web.xml文件中配置了DispatcherServlet，该文件会将传入的请求路由到适当的控制器方法。

web.xml

  1. <!DOCTYPE web-app PUBLIC
  2.  "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
  3.  "http://java.sun.com/dtd/web-app_2_3.dtd" >
  5. <web-app>
  6.     <display-name>Employee Management REST APIs</display-name>
  8.     <servlet>
  9.         <servlet-name>rest</servlet-name> 
  10.         <servlet-class>
  11.             org.springframework.web.servlet.DispatcherServlet
  12.         </servlet-class>
  13.         <load-on-startup>1</load-on-startup>
  14.     </servlet>
  16.     <servlet-mapping>
  17.         <servlet-name>rest</servlet-name>
  18.         <url-pattern>/api/rest/*</url-pattern>
  19.     </servlet-mapping>
  21. </web-app>

3. Spring 和 JPA 配置

在rest-servlet.xml文件中，我们已经配置了组件扫描和基于注解的配置支持。 随之，我们配置了实体管理器和数据源配置。

rest-servlet.xml

  1. <beans xmlns="http://www.springframework.org/schema/beans"
  2.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:context="http://www.springframework.org/schema/context"
  3.     xmlns:mvc="http://www.springframework.org/schema/mvc"
  4.     xmlns:jpa="http://www.springframework.org/schema/data/jpa"
  5.     xmlns:tx="http://www.springframework.org/schema/tx"
  6.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  7.     http://www.springframework.org/schema/beans/spring-beans.xsd
  8.     http://www.springframework.org/schema/context
  9.     http://www.springframework.org/schema/context/spring-context.xsd
  10.     http://www.springframework.org/schema/data/jpa 
  11.     http://www.springframework.org/schema/data/jpa/spring-jpa-1.0.xsd
  12.     http://www.springframework.org/schema/tx 
  13.     http://www.springframework.org/schema/tx/spring-tx-4.0.xsd
  14.     http://www.springframework.org/schema/mvc
  15.     http://www.springframework.org/schema/mvc/spring-mvc.xsd">
  17.     <context:component-scan base-package="com.howtodoinjava.demo" />
  18.     <mvc:annotation-driven />
  19.     <jpa:repositories base-package="com.howtodoinjava.demo.repository" entity-manager-factory-ref="emf"/>
  21.     <bean id="emf" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
  22.         <property name="packagesToScan" value="com.howtodoinjava.demo.model" />
  23.         <property name="dataSource" ref="dataSource" />
  25.         <property name="jpaProperties">
  26.             <props>
  27.                 <prop key="hibernate.show_sql">true</prop>
  28.                 <prop key="hibernate.format_sql">true</prop>
  29.                 <prop key="hibernate.hbm2ddl.auto">create</prop>
  30.                 <prop key="hibernate.dialect">org.hibernate.dialect.H2Dialect</prop>
  31.             </props>
  32.         </property>
  34.         <property name="persistenceProvider">
  35.             <bean class="org.hibernate.jpa.HibernatePersistenceProvider"></bean>
  36.         </property>
  38.     </bean>
  40.     <bean class="org.springframework.jdbc.datasource.SimpleDriverDataSource" id="dataSource">
  41.         <property name="driverClass" value="org.h2.Driver" />
  42.         <property name="url" value="jdbc:h2:mem:testdb;DB_CLOSE_DELAY=-1;TRACE_LEVEL_SYSTEM_OUT=2" />
  43.     </bean>
  45.     <tx:annotation-driven transaction-manager="transactionManager" />
  47.     <bean class="org.springframework.orm.jpa.JpaTransactionManager"  id="transactionManager">
  48.         <property name="dataSource" ref="dataSource" />
  49.     </bean>
  50. </beans>

4. 实体类

我们只有一个实体类，它将保留在数据库中，并将作为 REST API 的响应返回。

  • @Entity – JPA 注解，以使对象准备好存储在基于 JPA 的数据存储区中。
  • @Table – 数据存储中将存储此实体的表的名称。

阅读更多： JPA 2 持久性注解

Employee.java

  1. import java.io.Serializable;
  3. import javax.persistence.Entity;
  4. import javax.persistence.GeneratedValue;
  5. import javax.persistence.GenerationType;
  6. import javax.persistence.Id;
  7. import javax.persistence.Table;
  9. @Entity
  10. @Table(name = "tbl_employee")
  11. public class Employee implements Serializable {
  12.     private static final long serialVersionUID = 1L;
  14.     @Id
  15.     @GeneratedValue(strategy = GenerationType.IDENTITY)
  16.     private Long id;
  18.     private String firstName;
  20.     private String lastName;
  22.     private String email;
  24.     public Employee() {
  25.     }
  27.     //Getters and setters
  29.     @Override
  30.     public String toString() {
  31.         return "EmployeeVO [id=" + id + ", firstName=" + firstName + ", 
  32.                 lastName=" + lastName + ", email=" + email    + "]";
  33.     }
  34. }

5. 存储库

我们已将JpaRepository实现创建为EmployeeRepository，它提供了用于对员工实体执行搜索，获取，更新和删除操作的所有默认操作。

EmployeeRepository.java

  1. import org.springframework.data.jpa.repository.JpaRepository;
  2. import org.springframework.stereotype.Repository;
  4. import com.howtodoinjava.demo.model.Employee;
  6. @Repository
  7. public interface EmployeeRepository extends JpaRepository<Employee, Long> {
  9. }

6. REST 控制器

REST 控制器定义了可以调用以对员工资源执行操作的所有 CRUD 方法。

在给定的控制器中，@RestController注解指示方法返回的数据将直接写入响应主体中，而不呈现模板。 其他注解（@GetMapping，@PostMapping，@PutMapping和@DeleteMapping）将 HTTP 请求映射到相应的方法。

EmployeeRESTController.java

  1. import java.util.List;
  3. import org.springframework.beans.factory.annotation.Autowired;
  4. import org.springframework.http.MediaType;
  5. import org.springframework.web.bind.annotation.DeleteMapping;
  6. import org.springframework.web.bind.annotation.GetMapping;
  7. import org.springframework.web.bind.annotation.PathVariable;
  8. import org.springframework.web.bind.annotation.PostMapping;
  9. import org.springframework.web.bind.annotation.PutMapping;
  10. import org.springframework.web.bind.annotation.RequestBody;
  11. import org.springframework.web.bind.annotation.RequestMapping;
  12. import org.springframework.web.bind.annotation.RestController;
  14. import com.howtodoinjava.demo.model.Employee;
  15. import com.howtodoinjava.demo.repository.EmployeeRepository;
  17. @RestController
  18. @RequestMapping(value = "/employee-management", produces = { MediaType.APPLICATION_JSON_VALUE })
  19. public class EmployeeRESTController 
  20. {
  21.     @Autowired
  22.     private EmployeeRepository repository;
  24.     public EmployeeRepository getRepository() {
  25.         return repository;
  26.     }
  28.     public void setRepository(EmployeeRepository repository) {
  29.         this.repository = repository;
  30.     }
  32.     @GetMapping(value = "/employees")
  33.     public List<Employee> getAllEmployees() {
  34.         return repository.findAll();
  35.     }
  37.     @PostMapping("/employees")
  38.     Employee createOrSaveEmployee(@RequestBody Employee newEmployee) {
  39.         return repository.save(newEmployee);
  40.     }
  42.     @GetMapping("/employees/{id}")
  43.     Employee getEmployeeById(@PathVariable Long id) {
  44.         return repository.findById(id).get();
  45.     }
  47.     @PutMapping("/employees/{id}")
  48.     Employee updateEmployee(@RequestBody Employee newEmployee, @PathVariable Long id) {
  50.         return repository.findById(id).map(employee -> {
  51.             employee.setFirstName(newEmployee.getFirstName());
  52.             employee.setLastName(newEmployee.getLastName());
  53.             employee.setEmail(newEmployee.getEmail());
  54.             return repository.save(employee);
  55.         }).orElseGet(() -> {
  56.             newEmployee.setId(id);
  57.             return repository.save(newEmployee);
  58.         });
  59.     }
  61.     @DeleteMapping("/employees/{id}")
  62.     void deleteEmployee(@PathVariable Long id) {
  63.         repository.deleteById(id);
  64.     }
  65. }

7. Spring REST CRUD 操作演示

让我们测试一下 API 操作，以验证它们是否有效。

7.1. 创建员工

API Request

  1. HTTP POST : http://localhost:8080/SpringRestExample/api/rest/employee-management/employees
  3. {
  4.     "firstName": "lokesh",
  5.     "lastName": "gupta",
  6.     "email": "abc@gmail.com"
  7. }

API Response

  1. HTTP Response code : 200
  3. {
  4.     "id": 1,
  5.     "firstName": "lokesh",
  6.     "lastName": "gupta",
  7.     "email": "abc@gmail.com"
  8. }

创建更多的员工进行测试。

7.2. 获取员工集合

API Request

  1. HTTP GET : http://localhost:8080/SpringRestExample/api/rest/employee-management/employees

API Response

  1. HTTP Response code : 200
  3. [
  4.     {
  5.         "id": 1,
  6.         "firstName": "lokesh",
  7.         "lastName": "gupta",
  8.         "email": "abc@gmail.com"
  9.     },
  10.     {
  11.         "id": 2,
  12.         "firstName": "Amit",
  13.         "lastName": "Sharma",
  14.         "email": "xyz@gmail.com"
  15.     }
  16. ]

7.3. 按编号获取员工

API Request

  1. HTTP GET : http://localhost:8080/SpringRestExample/api/rest/employee-management/employees/1

API Response

  1. HTTP Response code : 200
  3. {
  4.     "id": 1,
  5.     "firstName": "lokesh",
  6.     "lastName": "gupta",
  7.     "email": "abc@gmail.com"
  8. }

7.4. 更新员工

API Request

  1. HTTP PUT : http://localhost:8080/SpringRestExample/api/rest/employee-management/employees/1
  3. {
  4.     "firstName": "Lucky",
  5.     "lastName": "Gupta",
  6.     "email": "abc@gmail.com"
  7. }

API Response

  1. HTTP Response code : 200
  3. {
  4.     "id": 1,
  5.     "firstName": "Lucky",
  6.     "lastName": "Gupta",
  7.     "email": "abc@gmail.com"
  8. }

7.5. 删除员工

API Request

  1. HTTP DELETE : http://localhost:8080/SpringRestExample/api/rest/employee-management/employees/1

API Response

  1. HTTP Response code : 200

学习愉快！

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