Spring Boot - Rest 模板

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Rest Template 用於建立使用 RESTful Web 服務的應用程式。您可以使用exchange()方法使用所有 HTTP 方法使用 web 服務。下面給出的程式碼展示瞭如何建立 Rest Template 的 Bean 來自動裝配 Rest Template 物件。

...
public class DemoApplication {
   public static void main(String[] args) {
      SpringApplication.run(DemoApplication.class, args);
   }
   @Bean
   public RestTemplate getRestTemplate() {
      return new RestTemplate();
   }
}

GET

使用 RestTemplate - exchange() 方法使用 GET API

假設此 URL https://:8080/products 返回以下 JSON，我們將使用以下程式碼使用 Rest Template 使用此 API 響應：

[
   {
      "id": "1",
      "name": "Honey"
   },
   {
      "id": "2",
      "name": "Almond"
   }
]

您需要遵循以下幾點來使用 API：

  • 自動裝配 Rest Template 物件。

  • 使用 HttpHeaders 設定請求頭。

  • 使用 HttpEntity 包裝請求物件。

  • 為 Exchange() 方法提供 URL、HttpMethod 和返回型別。

...
public class ConsumeWebService {
   @Autowired
   RestTemplate restTemplate;

   @GetMapping(value = "/template/products")
   public String getProductList() {
      HttpHeaders headers = new HttpHeaders();
      headers.setAccept(Arrays.asList(MediaType.APPLICATION_JSON));
      HttpEntity <String> entity = new HttpEntity<String>(headers);
      
      return restTemplate.exchange("
         https://:8080/products", HttpMethod.GET, entity, String.class).getBody();
   }
}

POST

使用 RestTemplate - exchange() 方法使用 POST API

假設此 URL https://:8080/products 返回如下所示的響應，我們將使用 Rest Template 使用此 API 響應。

下面給出的程式碼是請求體：

{
   "id":"3",
   "name":"Ginger"
}

下面給出的程式碼是響應體：

Product is created successfully

您需要遵循以下幾點來使用 API：

  • 自動裝配 Rest Template 物件。

  • 使用 HttpHeaders 設定請求頭。

  • 使用 HttpEntity 包裝請求物件。在這裡，我們將 Product 物件包裝起來發送到請求體。

  • 為 exchange() 方法提供 URL、HttpMethod 和返回型別。

...
public class ConsumeWebService {
   @Autowired
   RestTemplate restTemplate;

   @PostMapping(value = "/template/products")
   public String createProducts(@RequestBody Product product) {
      HttpHeaders headers = new HttpHeaders();
      headers.setAccept(Arrays.asList(MediaType.APPLICATION_JSON));
      HttpEntity<Product> entity = new HttpEntity<Product>(product,headers);
      
      return restTemplate.exchange(
         "https://:8080/products", HttpMethod.POST, entity, String.class).getBody();
   }
}

PUT

使用 RestTemplate - exchange() 方法使用 PUT API

假設此 URL https://:8080/products/3 返回以下響應，我們將使用 Rest Template 使用此 API 響應。

下面給出的程式碼是請求體：

{
   "name":"Indian Ginger"
}

下面給出的程式碼是響應體：

Product is updated successfully

您需要遵循以下幾點來使用 API：

  • 自動裝配 Rest Template 物件。

  • 使用 HttpHeaders 設定請求頭。

  • 使用 HttpEntity 包裝請求物件。在這裡，我們將 Product 物件包裝起來發送到請求體。

  • 為 exchange() 方法提供 URL、HttpMethod 和返回型別。

...
public class ConsumeWebService {
   @Autowired
   RestTemplate restTemplate;

   @PutMapping(value = "/template/products/{id}")
   public String updateProduct(@PathVariable("id") String id, @RequestBody Product product) {
      HttpHeaders headers = new HttpHeaders();
      headers.setAccept(Arrays.asList(MediaType.APPLICATION_JSON));
      HttpEntity<Product> entity = new HttpEntity<Product>(product,headers);
      
      return restTemplate.exchange(
         "https://:8080/products/"+id, HttpMethod.PUT, entity, String.class).getBody();
   }
}

DELETE

使用 RestTemplate - exchange() 方法使用 DELETE API

假設此 URL https://:8080/products/3 返回以下響應，我們將使用 Rest Template 使用此 API 響應。

下面顯示的程式碼行是響應體：

Product is deleted successfully

您需要遵循以下幾點來使用 API：

  • 自動裝配 Rest Template 物件。

  • 使用 HttpHeaders 設定請求頭。

  • 使用 HttpEntity 包裝請求物件。

  • 為 exchange() 方法提供 URL、HttpMethod 和返回型別。

...
public class ConsumeWebService {
   @Autowired
   RestTemplate restTemplate;

   @DeleteMapping(value = "/template/products/{id}")
   public String deleteProduct(@PathVariable("id") String id) {
      HttpHeaders headers = new HttpHeaders();
      headers.setAccept(Arrays.asList(MediaType.APPLICATION_JSON));
      HttpEntity<Product> entity = new HttpEntity<Product>(headers);
      
      return restTemplate.exchange(
         "https://:8080/products/"+id, HttpMethod.DELETE, entity, String.class).getBody();
   }
}

完整的 Rest Template Controller 類檔案如下：

ConsumeWebService.java

package com.tutorialspoint.demo.controller;

import java.util.Arrays;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.HttpEntity;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpMethod;
import org.springframework.http.MediaType;
import org.springframework.web.bind.annotation.DeleteMapping;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.PutMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;

import com.tutorialspoint.demo.model.Product;

@RestController
public class ConsumeWebService {
   @Autowired
   RestTemplate restTemplate;

   @GetMapping(value = "/template/products")
   public String getProductList() {
      HttpHeaders headers = new HttpHeaders();
      headers.setAccept(Arrays.asList(MediaType.APPLICATION_JSON));
      HttpEntity<String> entity = new HttpEntity<String>(headers);
      
      return restTemplate.exchange(
         "https://:8080/products", HttpMethod.GET, entity, String.class).getBody();
   }
   @PostMapping(value = "/template/products")
   public String createProducts(@RequestBody Product product) {
      HttpHeaders headers = new HttpHeaders();
      headers.setAccept(Arrays.asList(MediaType.APPLICATION_JSON));
      HttpEntity<Product> entity = new HttpEntity<Product>(product,headers);
      
      return restTemplate.exchange(
         "https://:8080/products", HttpMethod.POST, entity, String.class).getBody();
   }
   @PutMapping(value = "/template/products/{id}")
   public String updateProduct(@PathVariable("id") String id, @RequestBody Product product) {
      HttpHeaders headers = new HttpHeaders();
      headers.setAccept(Arrays.asList(MediaType.APPLICATION_JSON));
      HttpEntity<Product> entity = new HttpEntity<Product>(product,headers);
      
      return restTemplate.exchange(
         "https://:8080/products/"+id, HttpMethod.PUT, entity, String.class).getBody();
   }
   @DeleteMapping(value = "/template/products/{id}")
   public String deleteProduct(@PathVariable("id") String id) {
      HttpHeaders headers = new HttpHeaders();
      headers.setAccept(Arrays.asList(MediaType.APPLICATION_JSON));
      HttpEntity<Product> entity = new HttpEntity<Product>(headers);
      
      return restTemplate.exchange(
         "https://:8080/products/"+id, HttpMethod.DELETE, entity, String.class).getBody();
   }
}

充當 REST 服務的 Rest Controller 類，我們的 Web 服務正在呼叫。

ProductServiceController.java

package com.tutorialspoint.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.DeleteMapping;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.PutMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RestController;

import com.tutorialspoint.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);
   }
   
   @DeleteMapping(value = "/products/{id}")
   public ResponseEntity<Object> delete(@PathVariable("id") String id) { 
      productRepo.remove(id);
      return new ResponseEntity<>("Product is deleted successsfully", HttpStatus.OK);
   }
   
   @PutMapping(value = "/products/{id}")
   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);
   }
   
   @PostMapping(value = "/products")
   public ResponseEntity<Object> createProduct(@RequestBody Product product) {
      productRepo.put(product.getId(), product);
      return new ResponseEntity<>("Product is created successfully", HttpStatus.CREATED);
   }
   
   @GetMapping(value = "/products")
   public ResponseEntity<Object> getProduct() {
      return new ResponseEntity<>(productRepo.values(), HttpStatus.OK);
   }
}

Spring Boot Application 類 – DemoApplication.java 的程式碼如下：

DemoApplication.java

package com.tutorialspoint.demo;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
import org.springframework.web.client.RestTemplate;

@SpringBootApplication
public class DemoApplication {
   public static void main(String[] args) {
      SpringApplication.run(DemoApplication.class, args);
   }
   @Bean
   public RestTemplate getRestTemplate() {
      return new RestTemplate();
   }
}

Maven 構建 – pom.xml 的程式碼如下：

pom.xml

<?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>3.3.3</version>
      <relativePath/> <!-- lookup parent from repository -->
   </parent>
   <groupId>com.tutorialspoint</groupId>
   <artifactId>demo</artifactId>
   <version>0.0.1-SNAPSHOT</version>
   <name>demo</name>
   <description>Demo project for Spring Boot</description>
   <url/>
   <licenses>
      <license/>
   </licenses>
   <developers>
      <developer/>
   </developers>
   <scm>
      <connection/>
      <developerConnection/>
      <tag/>
      <url/>
   </scm>
   <properties>
      <java.version>21</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>

Gradle 構建 – build.gradle 的程式碼如下：

build.gradle

buildscript {
   ext {
      springBootVersion = '3.3.3'
   }
   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.tutorialspoint'
version = '0.0.1-SNAPSHOT'
sourceCompatibility = 21

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

您可以建立一個可執行的 JAR 檔案，並使用以下 Maven 或 Gradle 命令執行 Spring Boot 應用程式：

對於 Maven，您可以使用以下命令：

mvn clean install

“BUILD SUCCESS”之後，您可以在 target 目錄下找到 JAR 檔案。

對於 Gradle，您可以使用以下所示的命令：

gradle clean build

“BUILD SUCCESSFUL”之後，您可以在 build/libs 目錄下找到 JAR 檔案。

現在，使用以下命令執行 JAR 檔案：

java –jar <JARFILE>

現在，應用程式已在 Tomcat 埠 8080 上啟動。

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/

[32m :: Spring Boot :: [39m              [2m (v3.3.3)[0;39m

[2024-09-05T13:35:28Z] [org.springframework.boot.StartupInfoLogger] [main] [50] [INFO ] Starting DemoApplication using Java 21.0.3 with PID 9476 (E:\Dev\demo\target\classes started by Tutorialspoint in E:\Dev\demo)
[2024-09-05T13:35:28Z] [org.springframework.boot.SpringApplication] [main] [654] [INFO ] No active profile set, falling back to 1 default profile: "default"
[2024-09-05T13:35:29Z] [org.springframework.boot.web.embedded.tomcat.TomcatWebServer] [main] [111] [INFO ] Tomcat initialized with port 8080 (http)
[2024-09-05T13:35:29Z] [org.apache.juli.logging.DirectJDKLog] [main] [173] [INFO ] Initializing ProtocolHandler ["http-nio-8080"]
[2024-09-05T13:35:29Z] [org.apache.juli.logging.DirectJDKLog] [main] [173] [INFO ] Starting service [Tomcat]
[2024-09-05T13:35:29Z] [org.apache.juli.logging.DirectJDKLog] [main] [173] [INFO ] Starting Servlet engine: [Apache Tomcat/10.1.28]
[2024-09-05T13:35:29Z] [org.apache.juli.logging.DirectJDKLog] [main] [173] [INFO ] Initializing Spring embedded WebApplicationContext
[2024-09-05T13:35:29Z] [org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext] [main] [296] [INFO ] Root WebApplicationContext: initialization completed in 928 ms
[2024-09-05T13:35:29Z] [org.apache.juli.logging.DirectJDKLog] [main] [173] [INFO ] Starting ProtocolHandler ["http-nio-8080"]
[2024-09-05T13:35:29Z] [org.springframework.boot.web.embedded.tomcat.TomcatWebServer] [main] [243] [INFO ] Tomcat started on port 8080 (http) with context path '/'
[2024-09-05T13:35:29Z] [org.springframework.boot.StartupInfoLogger] [main] [56] [INFO ] Started DemoApplication in 1.852 seconds (process running for 2.829)

現在在 POSTMAN 應用程式中點選以下 URL，您可以看到輸出。

透過 Rest Template 獲取產品 - https://:8080/template/products

GET Products by Rest Template

建立產品 POST - https://:8080/template/products

Create Products POST

更新產品 PUT - https://:8080/template/products/3

Update Products POST

刪除產品 - https://:8080/template/products/3

Delete Products POST
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