用Java发送HTTP POST请求

lets assume this URL...

让我们假设这个URL……

http://www.example.com/page.php?id=10            

(Here id needs to be sent in a POST request)

(此id需要以POST request方式发送)

I want to send the id = 10 to the server's page.php, which accepts it in a POST method.

我想把id = 10发送到服务器的页面。php，在POST方法中接受它。

How can i do this from within Java?

如何在Java中实现这一点?

I tried this :

我试着这样的:

URL aaa = new URL("http://www.example.com/page.php");
URLConnection ccc = aaa.openConnection();

But I still can't figure out how to send it via POST

但是我还是不知道如何通过POST发送。

8 个解决方案

#1

Updated Answer:

Since some of the classes, in the original answer, are deprecated in the newer version of Apache HTTP Components, I'm posting this update.

由于在原始答案中，一些类在Apache HTTP组件的新版本中不被使用，所以我将发布此更新。

By the way, you can access the full documentation for more examples here.

顺便说一下，您可以在这里获得更多示例的完整文档。

HttpClient httpclient = HttpClients.createDefault();
HttpPost httppost = new HttpPost("http://www.a-domain.com/foo/");

// Request parameters and other properties.
List<NameValuePair> params = new ArrayList<NameValuePair>(2);
params.add(new BasicNameValuePair("param-1", "12345"));
params.add(new BasicNameValuePair("param-2", "Hello!"));
httppost.setEntity(new UrlEncodedFormEntity(params, "UTF-8"));

//Execute and get the response.
HttpResponse response = httpclient.execute(httppost);
HttpEntity entity = response.getEntity();

if (entity != null) {
    InputStream instream = entity.getContent();
    try {
        // do something useful
    } finally {
        instream.close();
    }
}

Original Answer:

I recommend to use Apache HttpClient. its faster and easier to implement.

我建议使用Apache HttpClient。它更快更容易实现。

PostMethod post = new PostMethod("http://jakarata.apache.org/");
NameValuePair[] data = {
    new NameValuePair("user", "joe"),
    new NameValuePair("password", "bloggs")
};
post.setRequestBody(data);
// execute method and handle any error responses.
...
InputStream in = post.getResponseBodyAsStream();
// handle response.

for more information check this url: http://hc.apache.org/

要了解更多信息，请查看这个url: http://hc.apache.org/

#2

Sending a POST request is easy in vanilla Java. Starting with a URL, we need t convert it to a URLConnection using url.openConnection();. After that, we need to cast it to a HttpURLConnection, so we can access its setRequestMethod() method to set our method. We finally say that we are going to send data over the connection.

在普通Java中，发送POST请求很容易。从URL开始，我们需要使用URL . openconnection()将其转换为URLConnection;在此之后，我们需要将其转换为HttpURLConnection，这样我们就可以访问它的setRequestMethod()方法来设置我们的方法。我们最后说，我们将通过连接发送数据。

URL url = new URL("https://www.example.com/login");
URLConnection con = url.openConnection();
HttpURLConnection http = (HttpURLConnection)con;
http.setRequestMethod("POST"); // PUT is another valid option
http.setDoOutput(true);

We then need to state what we are going to send:

然后我们需要说明我们要发送什么:

Sending a simple form

A normal POST coming from a http form has a well defined format. We need to convert our input to this format:

来自http表单的普通POST具有定义良好的格式。我们需要将输入转换为以下格式:

Map<String,String> arguments = new HashMap<>();
arguments.put("username", "root");
arguments.put("password", "sjh76HSn!"); // This is a fake password obviously
StringJoiner sj = new StringJoiner("&");
for(Map.Entry<String,String> entry : arguments.entrySet())
    sj.add(URLEncoder.encode(entry.getKey(), "UTF-8") + "=" 
         + URLEncoder.encode(entry.getValue(), "UTF-8"));
byte[] out = sj.toString().getBytes(StandardCharsets.UTF_8);
int length = out.length;

We can then attach our form contents to the http request with proper headers and send it.

然后，我们可以将我们的表单内容附加到具有适当头的http请求并将其发送出去。

http.setFixedLengthStreamingMode(length);
http.setRequestProperty("Content-Type", "application/x-www-form-urlencoded; charset=UTF-8");
http.connect();
try(OutputStream os = http.getOutputStream()) {
    os.write(out);
}
// Do something with http.getInputStream()

---

Sending JSON

We can also send json using java, this is also easy:

我们也可以用java发送json，这也很简单:

byte[] out = "{\"username\":\"root\",\"password\":\"password\"}" .getBytes(StandardCharsets.UTF_8);
int length = out.length;

http.setFixedLengthStreamingMode(length);
http.setRequestProperty("Content-Type", "application/json; charset=UTF-8");
http.connect();
try(OutputStream os = http.getOutputStream()) {
    os.write(out);
}
// Do something with http.getInputStream()

Remember that different servers accept different content-types for json, see this question.

请记住，不同的服务器接受不同的json内容类型，请参见这个问题。

---

Sending files with java post

Sending files can be considered more challenging to handle as the format is more complex. We are also going to add support for sending the files as a string, since we don't want to buffer the file fully into the memory.

由于格式更复杂，发送文件可能更具有挑战性。我们还将添加对将文件作为字符串发送的支持，因为我们不希望将文件完全缓冲到内存中。

For this, we define some helper methods:

为此，我们定义了一些辅助方法:

private void sendFile(OutputStream out, String name, InputStream in, String fileName) {
    String o = "Content-Disposition: form-data; name=\"" + URLEncoder.encode(name,"UTF-8") 
             + "\"; filename=\"" + URLEncoder.encode(filename,"UTF-8") + "\"\r\n\r\n";
    out.write(o.getBytes(StandardCharsets.UTF_8));
    byte[] buffer = new byte[2048];
    for (int n = 0; n >= 0; n = in.read(buffer))
        out.write(buffer, 0, n);
    out.write("\r\n".getBytes(StandardCharsets.UTF_8));
}

private void sendField(OutputStream out, String name, String field) {
    String o = "Content-Disposition: form-data; name=\"" 
             + URLEncoder.encode(name,"UTF-8") + "\"\r\n\r\n";
    out.write(o.getBytes(StandardCharsets.UTF_8));
    out.write(URLEncoder.encode(field,"UTF-8").getBytes(StandardCharsets.UTF_8));
    out.write("\r\n".getBytes(StandardCharsets.UTF_8));
}

We can then use these methods to create a multipart post request as follows:

然后我们可以使用这些方法来创建一个多部分的post请求，如下所示:

String boundary = UUID.randomUUID().toString();
byte[] boundaryBytes = 
           ("--" + boundary + "\r\n").getBytes(StandardCharsets.UTF_8);
byte[] finishBoundaryBytes = 
           ("--" + boundary + "--").getBytes(StandardCharsets.UTF_8);
http.setRequestProperty("Content-Type", 
           "multipart/form-data; charset=UTF-8; boundary=" + boundary);

// Enable streaming mode with default settings
http.setChunkedStreamingMode(0); 

// Send our fields:
try(OutputStream out = http.getOutputStream()) {
    // Send our header (thx Algoman)
    out.write(boundaryBytes);

    // Send our first field
    sendField(out, "username", "root");

    // Send a seperator
    out.write(boundaryBytes);

    // Send our second field
    sendField(out, "password", "toor");

    // Send another seperator
    out.write(boundaryBytes);

    // Send our file
    try(InputStream file = new FileInputStream("test.txt")) {
        sendFile(out, "identification", file, "text.txt");
    }

    // Finish the request
    out.write(finishBoundaryBytes);
}


// Do something with http.getInputStream()

#3

String rawData = "id=10";
String type = "application/x-www-form-urlencoded";
String encodedData = URLEncoder.encode( rawData, "UTF-8" ); 
URL u = new URL("http://www.example.com/page.php");
HttpURLConnection conn = (HttpURLConnection) u.openConnection();
conn.setDoOutput(true);
conn.setRequestMethod("POST");
conn.setRequestProperty( "Content-Type", type );
conn.setRequestProperty( "Content-Length", String.valueOf(encodedData.length()));
OutputStream os = conn.getOutputStream();
os.write(encodedData.getBytes());

#4

The first answer was great, but I had to add try/catch to avoid Java compiler errors.
Also, I had troubles to figure how to read the HttpResponse with Java libraries.

第一个答案很好，但是我必须添加try/catch以避免Java编译错误。此外，我还遇到了如何使用Java库读取HttpResponse的问题。

Here is the more complete code :

下面是更完整的代码:

/*
 * Create the POST request
 */
HttpClient httpClient = new DefaultHttpClient();
HttpPost httpPost = new HttpPost("http://example.com/");
// Request parameters and other properties.
List<NameValuePair> params = new ArrayList<NameValuePair>();
params.add(new BasicNameValuePair("user", "Bob"));
try {
    httpPost.setEntity(new UrlEncodedFormEntity(params, "UTF-8"));
} catch (UnsupportedEncodingException e) {
    // writing error to Log
    e.printStackTrace();
}
/*
 * Execute the HTTP Request
 */
try {
    HttpResponse response = httpClient.execute(httpPost);
    HttpEntity respEntity = response.getEntity();

    if (respEntity != null) {
        // EntityUtils to get the response content
        String content =  EntityUtils.toString(respEntity);
    }
} catch (ClientProtocolException e) {
    // writing exception to log
    e.printStackTrace();
} catch (IOException e) {
    // writing exception to log
    e.printStackTrace();
}

#5

A simple way using Apache HTTP Components is

使用Apache HTTP组件的一个简单方法是。

Request.Post("http://www.example.com/page.php")
            .bodyForm(Form.form().add("id", "10").build())
            .execute()
            .returnContent();

Take a look at the Fluent API

看看这个流畅的API。

#6

simplest way to send parameters with the post request:

用post请求发送参数的最简单方法:

String postURL = "http://www.example.com/page.php";

HttpPost post = new HttpPost(postURL);

List<NameValuePair> params = new ArrayList<NameValuePair>();
params.add(new BasicNameValuePair("id", "10"));

UrlEncodedFormEntity ent = new UrlEncodedFormEntity(params, "UTF-8");
post.setEntity(ent);

HttpClient client = new DefaultHttpClient();
HttpResponse responsePOST = client.execute(post);

You have done. now you can use responsePOST. Get response content as string:

你所做的。现在可以使用responsePOST了。以字符串形式获取响应内容:

BufferedReader reader = new BufferedReader(new  InputStreamReader(responsePOST.getEntity().getContent()), 2048);

if (responsePOST != null) {
    StringBuilder sb = new StringBuilder();
    String line;
    while ((line = reader.readLine()) != null) {
        System.out.println(" line : " + line);
        sb.append(line);
    }
    String getResponseString = "";
    getResponseString = sb.toString();
//use server output getResponseString as string value.
}

#7

I recomend use http-request built on apache http api.

我重新使用构建在apache http api上的http请求。

HttpRequest<String> httpRequest = HttpRequestBuilder.createPost("http://www.example.com/page.php", String.class)
.responseDeserializer(ResponseDeserializer.ignorableDeserializer()).build();

public void send(){
   String response = httpRequest.execute("id", "10").get();
}

#8

Call HttpURLConnection.setRequestMethod("POST") and HttpURLConnection.setDoOutput(true); Actually only the latter is needed as POST then becomes the default method.

调用HttpURLConnection.setRequestMethod(“后”)和HttpURLConnection.setDoOutput(真正的);实际上，POST成为默认方法时，只需要后者。