Spring Boot - 构建RESTful Web服务

Spring Boot为构建企业应用程序的RESTful Web服务提供了非常好的支持。本章将详细介绍如何使用Spring Boot构建RESTful Web服务。

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')

完整的构建配置文件Maven build - pom.xml的代码如下

<?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
   http://maven.apache.org/xsd/maven-4.0.0.xsd">

   <modelVersion>4.0.0</modelVersion>
   <groupId>com.codingdict</groupId>
   <artifactId>demo</artifactId>
   <version>0.0.1-SNAPSHOT</version>
   <packaging>jar</packaging>
   <name>demo</name>
   <description>Demo project for Spring Boot</description>

   <parent>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-parent</artifactId>
      <version>1.5.8.RELEASE</version>
      <relativePath/>
   </parent>

   <properties>
      <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
      <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
      <java.version>1.8</java.version>
   </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>
      </dependency>
   </dependencies>

   <build>
      <plugins>
         <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
         </plugin>
      </plugins>
   </build>

</project>

完整的构建配置文件Gradle Build - build.gradle的代码如下

buildscript {
   ext {
      springBootVersion = '1.5.8.RELEASE'
   }
   repositories {
      mavenCentral()
   }
   dependencies {
      classpath("org.springframework.boot:spring-boot-gradle-plugin:${springBootVersion}")
   }
}

apply plugin: 'java'
apply plugin: 'eclipse'
apply plugin: 'org.springframework.boot'

group = 'com.codingdict'
version = '0.0.1-SNAPSHOT'
sourceCompatibility = 1.8

repositories {
   mavenCentral()
}
dependencies {
   compile('org.springframework.boot:spring-boot-starter-web')
   testCompile('org.springframework.boot:spring-boot-starter-test')
}

在继续构建RESTful Web服务之前，建议您了解以下注释

RestController

@RestController注释用于定义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 {
}

请求映射

@RequestMapping注释用于定义访问REST端点的Request URI。我们可以定义Request方法来使用和生成对象。默认请求方法是GET。

@RequestMapping(value = "/products")
public ResponseEntity<Object> getProducts() { }

请求机构

@RequestBody注释用于定义请求正文内容类型。

public ResponseEntity<Object> createProduct(@RequestBody Product product) {
}

路径变量

@PathVariable注释用于定义自定义或动态请求URI。请求URI中的Path变量定义为花括号{}，如下所示

public ResponseEntity<Object> updateProduct(@PathVariable("id") String id) {
}

请求参数

@RequestParam注释用于从请求URL中读取请求参数。默认情况下，它是必需参数。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Request Body。您可以发送请求参数和路径变量来定义自定义或动态URL。

用于定义HTTP GET请求方法的示例代码如下所示。在此示例中，我们使用HashMap存储产品。请注意，我们使用POJO类作为要存储的产品。

这里，请求URI是/ products，它将从HashMap存储库返回产品列表。下面给出了包含GET方法REST Endpoint的控制器类文件。

package com.codingdict.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.codingdict.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存储Product，其中产品是POJO类。

这里，请求URI是/ products，它会在将产品存储到HashMap存储库后返回String。

package com.codingdict.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.codingdict.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更新现有产品，其中产品是POJO类。

这里的请求URI是/products/{id}，它将产品后的String返回到HashMap存储库。请注意，我们使用Path变量{id}来定义需要更新的产品ID。

package com.codingdict.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.codingdict.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删除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删除现有产品，即POJO类。

请求URI是/products/{id}，它将在从HashMap存储库中删除产品后返回String。我们使用Path变量{id}来定义需要删除的产品ID。

package com.codingdict.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.codingdict.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);
   }
}

本节为您提供完整的源代码集。请遵守以下代码了解其各自的功能

Spring Boot主应用程序类 - DemoApplication.java

package com.codingdict.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.codingdict.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 Controller类 - ProductServiceController.java

package com.codingdict.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.codingdict.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);
   }
}