我成功地使用这段代码通过GET方法发送带有一些参数的HTTP请求

void sendRequest(String request)
{
    // i.e.: request = "http://example.com/index.php?param1=a&param2=b&param3=c";
    URL url = new URL(request); 
    HttpURLConnection connection = (HttpURLConnection) url.openConnection();           
    connection.setDoOutput(true); 
    connection.setInstanceFollowRedirects(false); 
    connection.setRequestMethod("GET"); 
    connection.setRequestProperty("Content-Type", "text/plain"); 
    connection.setRequestProperty("charset", "utf-8");
    connection.connect();
}

现在我可能需要通过POST方法发送参数(即param1, param2, param3),因为它们非常长。 我想添加一个额外的参数,该方法(即字符串httpMethod)。

我怎样才能尽可能少地更改上面的代码,以便能够通过GET或POST发送参数?

我希望情况会有所改变

connection.setRequestMethod("GET");

to

connection.setRequestMethod("POST");

可以完成这个任务,但是参数仍然通过GET方法发送。

HttpURLConnection有任何方法可以帮助吗? 有什么有用的Java构造吗?

任何帮助都将不胜感激。


当前回答

import java.net.*;

public class Demo{

  public static void main(){

       String data = "data=Hello+World!";
       URL url = new URL("http://localhost:8084/WebListenerServer/webListener");
       HttpURLConnection con = (HttpURLConnection) url.openConnection();
       con.setRequestMethod("POST");
       con.setDoOutput(true);
       con.getOutputStream().write(data.getBytes("UTF-8"));
       con.getInputStream();

    }

}

其他回答

我用Boann的答案创建了一个更灵活的查询字符串构建器,支持列表和数组,就像php的http_build_query方法一样:

public static byte[] httpBuildQueryString(Map<String, Object> postsData) throws UnsupportedEncodingException {
    StringBuilder postData = new StringBuilder();
    for (Map.Entry<String,Object> param : postsData.entrySet()) {
        if (postData.length() != 0) postData.append('&');

        Object value = param.getValue();
        String key = param.getKey();

        if(value instanceof Object[] || value instanceof List<?>)
        {
            int size = value instanceof Object[] ? ((Object[])value).length : ((List<?>)value).size();
            for(int i = 0; i < size; i++)
            {
                Object val = value instanceof Object[] ? ((Object[])value)[i] : ((List<?>)value).get(i);
                if(i>0) postData.append('&');
                postData.append(URLEncoder.encode(key + "[" + i + "]", "UTF-8"));
                postData.append('=');            
                postData.append(URLEncoder.encode(String.valueOf(val), "UTF-8"));
            }
        }
        else
        {
            postData.append(URLEncoder.encode(key, "UTF-8"));
            postData.append('=');            
            postData.append(URLEncoder.encode(String.valueOf(value), "UTF-8"));
        }
    }
    return postData.toString().getBytes("UTF-8");
}

在GET请求中,参数作为URL的一部分发送。

在POST请求中,参数作为请求体发送,位于请求头之后。

要使用HttpURLConnection进行POST,需要在打开连接后将参数写入连接。

这段代码应该让你开始:

String urlParameters  = "param1=a&param2=b&param3=c";
byte[] postData       = urlParameters.getBytes( StandardCharsets.UTF_8 );
int    postDataLength = postData.length;
String request        = "http://example.com/index.php";
URL    url            = new URL( request );
HttpURLConnection conn= (HttpURLConnection) url.openConnection();           
conn.setDoOutput( true );
conn.setInstanceFollowRedirects( false );
conn.setRequestMethod( "POST" );
conn.setRequestProperty( "Content-Type", "application/x-www-form-urlencoded"); 
conn.setRequestProperty( "charset", "utf-8");
conn.setRequestProperty( "Content-Length", Integer.toString( postDataLength ));
conn.setUseCaches( false );
try( DataOutputStream wr = new DataOutputStream( conn.getOutputStream())) {
   wr.write( postData );
}

我强烈推荐构建在apache http api上的http-request。

对于你的案例,你可以看到例子:

private static final HttpRequest<String.class> HTTP_REQUEST = 
      HttpRequestBuilder.createPost("http://example.com/index.php", String.class)
           .responseDeserializer(ResponseDeserializer.ignorableDeserializer())
           .build();

public void sendRequest(String request){
     String parameters = request.split("\\?")[1];
     ResponseHandler<String> responseHandler = 
            HTTP_REQUEST.executeWithQuery(parameters);

   System.out.println(responseHandler.getStatusCode());
   System.out.println(responseHandler.get()); //prints response body
}

如果您对响应体不感兴趣

private static final HttpRequest<?> HTTP_REQUEST = 
     HttpRequestBuilder.createPost("http://example.com/index.php").build();

public void sendRequest(String request){
     ResponseHandler<String> responseHandler = 
           HTTP_REQUEST.executeWithQuery(parameters);
}

对于一般发送post请求与HTTP -request:阅读文档,看到我的答案HTTP post请求与JSON字符串在JAVA,发送HTTP post请求在JAVA, HTTP post使用JSON在JAVA

现在我要做一个HTTP请求类,它可能不是最有效的类,但它可以工作。 我从这个页面中收集了一些代码,并使其更加动态。

任何需要完整代码的人,我在下面附上了它。 关于如何使用它的示例,您可以查看main方法。

此外,如果你愿意改进在线课程,非常欢迎你来帮助我使这门课变得更好。

import java.net.*;
import java.util.*;
import java.nio.charset.*;
import java.io.*;
  
public class HttpRequest {
    
    
    String result = "";
    
    HttpRequest(String _url, String _method, Map<String, String> _postData, String _contentType) {
        
        try {
            URL url = new URL( _url );
            URLConnection con = url.openConnection();
            HttpURLConnection http = (HttpURLConnection)con;
            http.setRequestMethod(_method); // PUT is another valid option
            http.setDoOutput(true);         
            
            StringJoiner sj = new StringJoiner("&");
            for(Map.Entry<String,String> entry : _postData.entrySet())
                sj.add(URLEncoder.encode(entry.getKey(), "UTF-8") + "=" + entry.getValue());
                //sj.add(URLEncoder.encode(entry.getKey(), "UTF-8") + "=" + URLEncoder.encode(entry.getValue()));
            byte[] out = sj.toString().getBytes(StandardCharsets.UTF_8);
            int length = out.length;
            http.setFixedLengthStreamingMode(length);
            http.setRequestProperty("Content-Type", _contentType);
            http.setRequestProperty( "charset", "utf-8");
            http.setRequestProperty( "Content-Length", Integer.toString( length ));
            http.setInstanceFollowRedirects( false );
            http.setUseCaches( false );
            http.connect();
            try(OutputStream os = http.getOutputStream()) {
                os.write(out);
            }
            if (http.getResponseCode() == HttpURLConnection.HTTP_OK) {
                try (BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(http.getInputStream()))) {
                String line;
                while ((line = bufferedReader.readLine()) != null) {
                  result = result + line;
                }
            }
          } else {
            System.out.println("Bad response!");
          }
        }catch (IOException e) {
            // writing exception to log
            e.printStackTrace();
        }
        
    }
    
    
    HttpRequest(String _url, String _method, Map<String, String> _postData) {
        this(_url, _method, _postData, "text/html");
    }
    
    HttpRequest(String _url, String _method) {
        this(_url, _method, new HashMap<String, String>());
    }
    
    HttpRequest(String _url) {
        this(_url, "GET");
    }
    
    
    public String toString() {
        return result;
    }
    
    
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Map<String, String> postData = new HashMap<String, String>();
        postData.putIfAbsent("email", "test@test.com");
        postData.putIfAbsent("password", "test");
        
        HttpRequest result = new HttpRequest("https://httpbin.org/anything", "POST", postData, "application/x-www-form-urlencoded");
        System.out.println(result.toString());
    }
}

这个答案涵盖了使用自定义Java POJO的POST调用的特定情况。

使用Gson的maven依赖项将Java对象序列化为JSON。

使用下面的依赖项安装Gson。

<dependency>
  <groupId>com.google.code.gson</groupId>
  <artifactId>gson</artifactId>
  <version>2.8.5</version>
  <scope>compile</scope>
</dependency>

对于那些使用gradle的人可以使用下面的

dependencies {
implementation 'com.google.code.gson:gson:2.8.5'
}

使用的其他导入:

import org.apache.http.HttpResponse;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.entity.*;
import org.apache.http.impl.client.CloseableHttpClient;
import com.google.gson.Gson;

现在,我们可以继续使用Apache提供的HttpPost

private CloseableHttpClient httpclient = HttpClients.createDefault();
HttpPost httppost = new HttpPost("https://example.com");

Product product = new Product(); //custom java object to be posted as Request Body
    Gson gson = new Gson();
    String client = gson.toJson(product);

    httppost.setEntity(new StringEntity(client, ContentType.APPLICATION_JSON));
    httppost.setHeader("RANDOM-HEADER", "headervalue");
    //Execute and get the response.
    HttpResponse response = null;
    try {
        response = httpclient.execute(httppost);
    } catch (IOException e) {
        throw new InternalServerErrorException("Post fails");
    }
    Response.Status responseStatus = Response.Status.fromStatusCode(response.getStatusLine().getStatusCode());
    return Response.status(responseStatus).build();

上面的代码将返回从POST调用接收到的响应代码