Spring Boot 構建一個 RESTful Web Service

本文轉載自查看原文 2018-04-12 15:23 889

1 項目目標：

構建一個 web service，接收get 請求

http://localhost:8080/greeting

響應一個json 結果：

{"id":1,"content":"Hello, World!"}

可以在請求中添加自定義參數name

http://localhost:8080/greeting?name=User

響應結果：

{"id":1,"content":"Hello, User!"}

2 環境准備：

 1） 開發工具 IntelliJ IDEA  （自己下載安裝） cdkey 網上找吧。

 2） JAVA JDK1.8+   （http://www.oracle.com/technetwork/java/javase/downloads/jdk8-downloads-2133151.html）   //  本示例是用的 jdk1.8.0_172   Windows x64

    2).1  配置 JDK 環境變量。 http://www.cnblogs.com/iampkm/p/8805493.html

          根據JDK 的安裝路徑，在系統環境變量中配置 （JAVA_HOME,PATH,CLASSPATH）

 3） 配置Maven 3.2+   下載：https://maven.apache.org/download.cgi  （我用的是3.5）

   3）.1 新建本地庫目錄repository （位置可以隨意）。我是在apache-maven-3.5.2 目錄下 創建的。

3) .2 settings.xml 中配置本地庫。打開maven 目錄下的 conf/settings.xml 文件，修改自己的庫目錄

3）.3 settings.xml 中修改maven鏡像下載地址為淘寶,在配置文件中，加入紅色代碼部分

<mirrors>
    
    <mirror>
    <id>alimaven</id>
    <name>aliyun maven</name>
    <url>http://maven.aliyun.com/nexus/content/groups/public/</url>
    <mirrorOf>central</mirrorOf>
    </mirror>
</mirrors>

3) .4在idea 中，把maven 改成本地位置。打開Idea ，選擇File > Settings > 按照如下圖配置本地maven 的三個位置即可。

3 新建項目greeting。啟用spring boot 初始化

輸入項目名，我本地取名 quickstart

選擇web

創建一個資源 java 類 model

Create a resource representation class

Now that you’ve set up the project and build system, you can create your web service.

Begin the process by thinking about service interactions.

The service will handle GET requests for /greeting, optionally with a name parameter in the query string. The GET request should return a 200 OK response with JSON in the body that represents a greeting. It should look something like this:

package com.example.qucikstart;

public class Greeting {

    private final long id;
    private final String content;

    public Greeting(long id, String content) {
        this.id = id;
        this.content = content;
    }

    public long getId() {
        return id;
    }

    public String getContent() {
        return content;
    }
}

這個就是返回的結果內：該類在返回時，會自動被轉換成json格式

{
    "id": 1,
    "content": "Hello, World!"
}

創建一個java 控制類 GreetingController

Create a resource controller

In Spring’s approach to building RESTful web services, HTTP requests are handled by a controller. These components are easily identified by the @RestController annotation, and the GreetingController below handles GET requests for /greeting by returning a new instance of the Greeting class:

package com.example.qucikstart;

import java.util.concurrent.atomic.AtomicLong;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class GreetingController {
    private static final  String template ="hello,%s!";
    private  final  AtomicLong counter = new AtomicLong();

    @RequestMapping("/Greeting")
    public Greeting greeting(@RequestParam(value="name",defaultValue="world") String name) {
        return new Greeting(counter.incrementAndGet(),
                String.format(template, name));
    }
}

This controller is concise and simple, but there’s plenty going on under the hood. Let’s break it down step by step.

The @RequestMapping annotation ensures that HTTP requests to /greeting are mapped to the greeting() method.

當請求 RequestMapping 注解會把 greeting 的請求，映射到 greeting 方法。

確保main 程序用springboot 啟動

Make the application executable

Although it is possible to package this service as a traditional WAR file for deployment to an external application server, the simpler approach demonstrated below creates a standalone application. You package everything in a single, executable JAR file, driven by a good old Java main() method. Along the way, you use Spring’s support for embedding the Tomcat servlet container as the HTTP runtime, instead of deploying to an external instance.

package com.example.qucikstart;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class QucikstartApplication {

    public static void main(String[] args) {
        SpringApplication.run(QucikstartApplication.class, args);
    }
}

項目結構：