上一节:
下一节:

  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。
    注 –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
上一节:
下一节: