Spring Boot 构建RESTful Web服务



  • 构建RESTful Web服务

    Spring Boot为为企业应用程序构建RESTful Web服务提供了很好的支持。本章将详细说明有关使用Spring Boot构建RESTful Web服务的信息。
    –为了构建RESTful Web服务,我们需要将Spring Boot Starter Web依赖项添加到构建配置文件中。
    如果您是Maven用户,请使用以下代码在pom.xml文件中添加以下依赖项-
    
    <dependency>
       <groupId>org.springframework.boot</groupId>
       <artifactId>spring-boot-starter-web</artifactId>    
    </dependency>
    
    
    如果您是Gradle用户,请使用以下代码在build.gradle文件中添加以下依赖项。
    
    compile('org.springframework.boot:spring-boot-starter-web')
    
    
    下面给出了完整的构建配置文件Maven 构建 – pom.xml的代码-
    
    <?xml version="1.0" encoding="UTF-8"?>
    <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
            xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
            <modelVersion>4.0.0</modelVersion>
            <parent>
                    <groupId>org.springframework.boot</groupId>
                    <artifactId>spring-boot-starter-parent</artifactId>
                    <version>2.3.0.BUILD-SNAPSHOT</version>
                    <relativePath/> <!-- lookup parent from repository -->
            </parent>
            <groupId>com.jc2182</groupId>
            <artifactId>demo</artifactId>
            <version>0.0.1-SNAPSHOT</version>
            <!-- <packaging>war</packaging> -->
            <name>demo</name>
            <description>Demo project for Spring Boot</description>
    
            <properties>
                    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
            <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
            <java.version>1.8</java.version>
            <start-class>com.jc2182.demo.DemoApplication</start-class>
            </properties>
    
            <dependencies>
                    <dependency>
                            <groupId>org.springframework.boot</groupId>
                            <artifactId>spring-boot-starter-web</artifactId>
                    </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>
            </dependencies>
    
            <build>
                    <plugins>
                            <plugin>
                                    <groupId>org.springframework.boot</groupId>
                                    <artifactId>spring-boot-maven-plugin</artifactId>
                            </plugin>
                    </plugins>
            </build>
    
            <repositories>
                    <repository>
                            <id>spring-milestones</id>
                            <name>Spring Milestones</name>
                            <url>https://repo.spring.io/milestone</url>
                    </repository>
                    <repository>
                            <id>spring-snapshots</id>
                            <name>Spring Snapshots</name>
                            <url>https://repo.spring.io/snapshot</url>
                            <snapshots>
                                    <enabled>true</enabled>
                            </snapshots>
                    </repository>
            </repositories>
            <pluginRepositories>
                    <pluginRepository>
                            <id>spring-milestones</id>
                            <name>Spring Milestones</name>
                            <url>https://repo.spring.io/milestone</url>
                    </pluginRepository>
                    <pluginRepository>
                            <id>spring-snapshots</id>
                            <name>Spring Snapshots</name>
                            <url>https://repo.spring.io/snapshot</url>
                            <snapshots>
                                    <enabled>true</enabled>
                            </snapshots>
                    </pluginRepository>
            </pluginRepositories>
    
    </project>
    
    
    下面给出了完整的构建配置文件Gradle 构建 – build.gradle的代码-
    
    plugins {
            id 'org.springframework.boot' version '2.3.0.BUILD-SNAPSHOT'
            id 'io.spring.dependency-management' version '1.0.9.RELEASE'
            id 'java'
            id 'war'
            id 'application'
    }
    
    group = 'com.jc2182'
    version = '0.0.1-SNAPSHOT'
    sourceCompatibility = '1.8'
    mainClassName = "com.jc2182.demo.DemoApplication"
    
    repositories {
            mavenCentral()
            maven { url 'https://repo.spring.io/milestone' }
            maven { url 'https://repo.spring.io/snapshot' }
    }
    
    dependencies {
            implementation 'org.springframework.boot:spring-boot-starter-web'
            testImplementation('org.springframework.boot:spring-boot-starter-test') {
                    exclude group: 'org.junit.vintage', module: 'junit-vintage-engine'
            }
    }
    
    test {
            useJUnitPlatform()
    }
    
    
    在继续构建RESTful Web服务之前,建议您了解以下注解
  • @RestController

    @RestController注解用于定义RESTful Web服务。它提供JSON,XML和自定义响应。其语法如下所示-
    
    @RestController
    public class ProductServiceController { 
    }
    
    
  • @RequestMapping

    @RequestMapping注解用于定义请求URI来访问REST端点。我们可以定义Request方法来使用和产生对象。默认请求方法是GET。
    
    @RequestMapping(value = "/products")
    public ResponseEntity<Object> getProducts() { }
    
    
  • @RequestBody

    @RequestBody注解用于定义请求正文内容类型。
    
    public ResponseEntity<Object> createProduct(@RequestBody Product product) {
    }
    
    
  • @PathVariable

    @PathVariable注解用于定义自定义或动态请求URI。请求URI中的Path变量定义为大括号{},如下所示-
    
    public ResponseEntity<Object> updateProduct(@PathVariable("id") String id) {
    }
    
    
  • @RequestParam

    @RequestParam 注解用于从请求URL读取请求参数。默认情况下,它是必需的参数。我们还可以为请求参数设置默认值,如下所示-
    
    public ResponseEntity<Object> getProduct(
       @RequestParam(value = "name", required = false, defaultValue = "honey") String name) {
    }
    
    
  • GET API

    默认的HTTP请求方法是GET。此方法不需要任何请求正文。您可以发送请求参数和路径变量来定义定制URL或动态URL。下面显示了定义HTTP GET请求方法的示例代码。在此示例中,我们使用HashMap来存储产品。请注意,我们使用POJO类作为要存储的产品。 在这里,请求URI是/products,它将返回HashMap存储库中的产品列表。下面给出了包含GET方法REST Endpoint的控制器类文件。
    
    package com.jc2182.demo.controller;
    
    import java.util.HashMap;
    import java.util.Map;
    
    import org.springframework.http.HttpStatus;
    import org.springframework.http.ResponseEntity;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.bind.annotation.RestController;
    
    import com.jc2182.demo.model.Product;
    
    @RestController
    public class ProductServiceController {
       private static Map<String, Product> productRepo = new HashMap<>();
       static {
          Product honey = new Product();
          honey.setId("1");
          honey.setName("Honey");
          productRepo.put(honey.getId(), honey);
          
          Product almond = new Product();
          almond.setId("2");
          almond.setName("Almond");
          productRepo.put(almond.getId(), almond);
       }
       @RequestMapping(value = "/products")
       public ResponseEntity<Object> getProduct() {
          return new ResponseEntity<>(productRepo.values(), HttpStatus.OK);
       }
    }
    
    
  • POST API

    HTTP POST请求用于创建资源。此方法包含请求正文。我们可以发送请求参数和路径变量来定义自定义或动态URL。以下示例显示了用于定义HTTP POST请求方法的示例代码。在此示例中,我们使用HashMap来存储产品,其中产品是POJO类。在这里,请求URI是/products,在将产品存储到HashMap存储库后,它将返回String。
    
    package com.jc2182.demo.controller;
    
    import java.util.HashMap;
    import java.util.Map;
    
    import org.springframework.http.HttpStatus;
    import org.springframework.http.ResponseEntity;
    import org.springframework.web.bind.annotation.RequestBody;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.bind.annotation.RequestMethod;
    import org.springframework.web.bind.annotation.RestController;
    
    import com.jc2182.demo.model.Product;
    
    @RestController
    public class ProductServiceController {
       private static Map<String, Product> productRepo = new HashMap<>();
       
       @RequestMapping(value = "/products", method = RequestMethod.POST)
       public ResponseEntity<Object> createProduct(@RequestBody Product product) {
          productRepo.put(product.getId(), product);
          return new ResponseEntity<>("Product is created successfully", HttpStatus.CREATED);
       }
    }
    
    
  • PUT API

    HTTP PUT请求用于更新现有资源。此方法包含一个请求正文。我们可以发送请求参数和路径变量来定义自定义或动态URL。下面给出的示例显示了如何定义HTTP PUT请求方法。在此示例中,我们使用HashMap来更新现有产品,其中产品是POJO类。这里的请求URI是/products/{id},它将在产品放入HashMap存储库后返回String。请注意,我们使用了路径变量{id},该变量定义了需要更新的产品ID。
    
    package com.jc2182.demo.controller;
    
    import java.util.HashMap;
    import java.util.Map;
    
    import org.springframework.http.HttpStatus;
    import org.springframework.http.ResponseEntity;
    import org.springframework.web.bind.annotation.PathVariable;
    import org.springframework.web.bind.annotation.RequestBody;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.bind.annotation.RequestMethod;
    import org.springframework.web.bind.annotation.RestController;
    import com.jc2182.demo.model.Product;
    
    @RestController
    public class ProductServiceController {
       private static Map<String, Product> productRepo = new HashMap<>();
       
       @RequestMapping(value = "/products/{id}", method = RequestMethod.PUT)
       public ResponseEntity<Object> updateProduct(@PathVariable("id") String id, @RequestBody Product product) { 
          productRepo.remove(id);
          product.setId(id);
          productRepo.put(id, product);
          return new ResponseEntity<>("Product is updated successsfully", HttpStatus.OK);
       }   
    }
    
    
  • DELETE API

    HTTP DELETE请求用于删除现有资源。此方法不包含任何请求正文。我们可以发送请求参数和路径变量来定义自定义或动态URL。下面给出的示例显示了如何定义HTTP DELETE请求方法。在此示例中,我们使用HashMap删除了现有的产品,该产品是POJO类。请求URI为/products/{id},从HashMap存储库中删除产品后,它将返回String。我们使用了路径变量{id},该变量定义了需要删除的产品ID。
    
    package com.jc2182.demo.controller;
    
    import java.util.HashMap;
    import java.util.Map;
    
    import org.springframework.http.HttpStatus;
    import org.springframework.http.ResponseEntity;
    import org.springframework.web.bind.annotation.PathVariable;
    import org.springframework.web.bind.annotation.RequestBody;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.bind.annotation.RequestMethod;
    import org.springframework.web.bind.annotation.RestController;
    
    import com.jc2182.demo.model.Product;
    
    @RestController
    public class ProductServiceController {
       private static Map<String, Product> productRepo = new HashMap<>();
       
       @RequestMapping(value = "/products/{id}", method = RequestMethod.DELETE)
       public ResponseEntity<Object> delete(@PathVariable("id") String id) { 
          productRepo.remove(id);
          return new ResponseEntity<>("Product is deleted successsfully", HttpStatus.OK);
       }
    }
    
    
  • 完整代码及请求示例

    本节为您提供完整的源代码集。请遵守以下代码以了解其各自的功能:
    Spring Boot主应用程序类 – DemoApplication.java-
    
    package com.jc2182.demo;
    
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    
    @SpringBootApplication
    public class DemoApplication {
       public static void main(String[] args) {
          SpringApplication.run(DemoApplication.class, args);
       }
    }
    
    
    POJO类– Product.java
    
    package com.jc2182.demo.model;
    
    public class Product {
       private String id;
       private String name;
    
       public String getId() {
          return id;
       }
       public void setId(String id) {
          this.id = id;
       }
       public String getName() {
          return name;
       }
       public void setName(String name) {
          this.name = name;
       }
    }
    
    
    Rest控制器类– ProductServiceController.java
    
    package com.jc2182.demo.controller;
    
    import java.util.HashMap;
    import java.util.Map;
    
    import org.springframework.http.HttpStatus;
    import org.springframework.http.ResponseEntity;
    import org.springframework.web.bind.annotation.PathVariable;
    import org.springframework.web.bind.annotation.RequestBody;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.bind.annotation.RequestMethod;
    import org.springframework.web.bind.annotation.RestController;
    
    import com.jc2182.demo.model.Product;
    
    @RestController
    public class ProductServiceController {
       private static Map<String, Product> productRepo = new HashMap<>();
       static {
          Product honey = new Product();
          honey.setId("1");
          honey.setName("Honey");
          productRepo.put(honey.getId(), honey);
          
          Product almond = new Product();
          almond.setId("2");
          almond.setName("Almond");
          productRepo.put(almond.getId(), almond);
       }
       
       @RequestMapping(value = "/products/{id}", method = RequestMethod.DELETE)
       public ResponseEntity<Object> delete(@PathVariable("id") String id) { 
          productRepo.remove(id);
          return new ResponseEntity<>("Product is deleted successsfully", HttpStatus.OK);
       }
       
       @RequestMapping(value = "/products/{id}", method = RequestMethod.PUT)
       public ResponseEntity<Object> updateProduct(@PathVariable("id") String id, @RequestBody Product product) { 
          productRepo.remove(id);
          product.setId(id);
          productRepo.put(id, product);
          return new ResponseEntity<>("Product is updated successsfully", HttpStatus.OK);
       }
       
       @RequestMapping(value = "/products", method = RequestMethod.POST)
       public ResponseEntity<Object> createProduct(@RequestBody Product product) {
          productRepo.put(product.getId(), product);
          return new ResponseEntity<>("Product is created successfully", HttpStatus.CREATED);
       }
       
       @RequestMapping(value = "/products")
       public ResponseEntity<Object> getProduct() {
          return new ResponseEntity<>(productRepo.values(), HttpStatus.OK);
       }
    }
    
    
    您可以创建一个可执行的JAR文件,并使用以下Maven或Gradle命令运行spring boot应用程序,如下所示- 对于Maven,请使用下面显示的命令
    
    mvn clean install
    
    
    在“BUILD SUCCESS”提示之后,您可以在target目录下找到JAR文件。
    对于Gradle,请使用下面显示的命令-
    
    gradle clean build
    
    
    在“BUILD SUCCESSFUL”之后,您可以在build/libs目录下找到JAR文件。
    您可以使用下面显示的命令来运行JAR文件-
    
    java –jar <JARFILE>
    
    
    这将在Tomcat端口8080上启动应用程序
    现在,在POSTMAN应用程序中访问下面显示的URL,然后查看输出。
    GET API URL是 - http://localhost:8080/products
    restful
    POST API URL是 - http://localhost:8080/products
    restful
    PUT API URL是 - http://localhost:8080/products/3
    restful
    DELETE API URL是 - http://localhost:8080/products/3
    restful