Java基于HttpClient实现RPC的示例

时间:2022-06-17 23:49:03

1 HttpClient简介

在JDK中java.net包下提供了用户HTTP访问的基本功能,但是它缺少灵活性或许多应用所需要的功能。

​ HttpClient起初是Apache Jakarta Common 的子项目。用来提供高效的、最新的、功能丰富的支持 HTTP 协议的客户端编程工具包,并且它支持 HTTP 协议最新的版本。2007年成为*项目。

​ 通俗解释:HttpClient可以实现使用Java代码完成标准HTTP请求及响应。

2 代码实现

2.1 服务端

新建项目HttpClientServer

2.1.1 新建控制器

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com.mrshun.controller.DemoController
 
@Controller
public class DemoController {
    @RequestMapping("/demo")
    @ResponseBody
    public String demo(String param){
        return "demo"+param;
    }
}

2.1.2 新建启动器

新建启动器

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com.mrshun.HttpClientServerApplication
 
@SpringBootApplication
public class HttpClientServerApplication {
    public static void main(String[] args) {
    SpringApplication.run(HttpClientServerApplication.class,args);
    }
}

2.2 客户端

新建HttpClientDemo项目

2.2.1 添加依赖

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<dependencies>
    <dependency>
        <groupId>org.apache.httpcomponents</groupId>
        <artifactId>httpclient</artifactId>
        <version>4.5.10</version>
    </dependency>
</dependencies>

2.2.2 新建类

新建com.mrshun.HttpClientDemo,编写主方法。

2.2.2.1 使用GET方法访问

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public static void main(String[] args) {
    try {
     //创建http工具(理解成:浏览器) 发起请求,解析响应
        CloseableHttpClient httpClient = HttpClients.createDefault();
        //请求路径
        URIBuilder uriBuilder = new URIBuilder("http://localhost:8080/demo");
        uriBuilder.addParameter("param", "get123");
        //创建HttpGet请求对象
        HttpGet get = new HttpGet(uriBuilder.build());
        //创建响应对象
        CloseableHttpResponse response = httpClient.execute(get);
        //由于响应体是字符串,因此把HttpEntity类型转换为字符串类型,并设置字符编码
        String result = EntityUtils.toString(response.getEntity(), "utf-8");
        //输出结果
        System.out.println(result);
        //释放资源
        response.close();
        httpClient.close();
    } catch (URISyntaxException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }
}

2.2.2.2 使用POST方式访问

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public class HttpClientDemo {
    public static void main(String[] args) {
        try {
         //创建http工具(理解成:浏览器) 发起请求,解析响应
            CloseableHttpClient httpClient = HttpClients.createDefault();
            //创建HttpPOST请求对象
            HttpPost post = new HttpPost("http://localhost:8080/demo");
            //所有请求参数
            List<NameValuePair> params = new ArrayList<>();
            params.add(new BasicNameValuePair("param","123"));
            //创建HttpEntity接口的文本实现类的对象,放入参数并设置编码
            HttpEntity httpEntity = new UrlEncodedFormEntity(params,"utf-8");
            //放入到HttpPost对象中
            post.setEntity(httpEntity);           
            //创建响应对象
            CloseableHttpResponse response = httpClient.execute(post);
            //由于响应体是字符串,因此把HttpEntity类型转换为字符串类型
            String result = EntityUtils.toString(response.getEntity());
            //输出结果
            System.out.println(result);
            //释放资源
            response.close();
            httpClient.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

3. Jackson用法

3.1 把对象转换为json字符串

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ObjectMapper objectMapper = new ObjectMapper();
People peo = new People();
objectMapper.writeValueAsString(peo);

3.2 把json字符串转换为对象

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ObjectMapper objectMapper = new ObjectMapper();
People peo = objectMapper.readValue(content, People.class);

3.3 把json字符串转换为List集合

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ObjectMapper objectMapper = new ObjectMapper();
JavaType javaType = objectMapper.getTypeFactory().constructParametricType(List.class, People.class);
List<People> list = objectMapper.readValue(content, javaType);

4 HttpClient请求包含JSON

4.1 java代码实现

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public class HttpClientDemo {
    public static void main(String[] args) {
        try {
            CloseableHttpClient httpClient = HttpClients.createDefault();
            HttpPost post = new HttpPost("http://localhost:8080/demo");
            HttpEntity httpEntity= null;
String json = "{}";
            StringEntity entity = new StringEntity(json, ContentType.APPLICATION_JSON);
            post.setEntity(entity);
            CloseableHttpResponse response = httpClient.execute(post);
            String result = EntityUtils.toString(response.getEntity());
            System.out.println(result);
            response.close();
            httpClient.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

5 控制器接口参数

@RequestBody把请求体中流数据转换为指定的对象。多用在请求参数是json数据且请求的Content-Type=”application/json”

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@RequestMapping("/demo4")
@ResponseBody
public String demo4(@RequestBody List<People> list) {
    System.out.println(list);
    return list.toString();
}

6 Ajax发送json参数写法

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var json = '[{"id":123,"name":"mrshun"},{"id":123,"name":"zhangyongshun"}]';
 $.ajax({
     url:'/demo5',
     type:'post',
     success:function(data){
         alert(data);
         for(var i = 0 ;i<data.length;i++){
 
             alert(data[i].id +"  "+data[i].name);
         }
     },
     contentType:'application/json',//请求体中内容类型
     dataType:'json',//响应内容类型。
     data:json
 });

7 跨域

  • 跨域:协议、ip、端口中只要有一个不同就是跨域请求。
  • 同源策略:浏览器默认只允许ajax访问同源(协议、ip、端口都相同)内容。

解决同源策略:

​ 在控制器接口上添加@CrossOrigin。表示允许跨域。本质在响应头中添加Access-Control-Allow-Origin: *

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var json = '[{"id":123,"name":"mrshun"},{"id":456,"name":"zhangyongshun"}]';
 $.ajax({
     url:'/demo5',
     type:'post',
     success:function(data){
         alert(data);
         for(var i = 0 ;i<data.length;i++){
 
             alert(data[i].id +"  "+data[i].name);
         }
     },
     contentType:'application/json',//请求体中内容类型
     dataType:'json',//响应内容类型。
     data:json
 });

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原文链接:https://blog.csdn.net/qq_46144237/article/details/120751147