Question

我尝试使用DataOutputStream发送POST数据并获取响应数据。

我是这样编码的。

    String urlParameters = "table=page&format=xml";

    out.println(urlParameters+"<br/><br/><br/>");

    String searchUrl = "http://localhost:8081/WebTest/test.jsp";
    URL url = new URL(searchUrl); 
    HttpURLConnection connection = (HttpURLConnection) url.openConnection();           
    connection.setDoOutput(true);
    connection.setDoInput(true);
    connection.setInstanceFollowRedirects(false); 
    connection.setRequestMethod("POST"); 
    connection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded"); 
    connection.setRequestProperty("charset", "utf-8");
    connection.setRequestProperty("Content-Length", ""+Integer.toString(urlParameters.getBytes().length));
    connection.setUseCaches (false);

    DataOutputStream wr = new DataOutputStream(connection.getOutputStream());
    wr.writeUTF(urlParameters);
    wr.flush();
    wr.close();

    if( connection.getResponseCode() == 200){

        XMLInputFactory xmlFactory = XMLInputFactory.newInstance();
        XMLStreamReader reader = xmlFactory.createXMLStreamReader(new InputStreamReader(connection.getInputStream(),"UTF-8"));

        try{
            while (reader.hasNext()) {
                Integer eventType = reader.next();
                if (eventType.equals(XMLStreamReader.START_ELEMENT)){
                    out.print(" " + reader.getName() + "<br/>");
                }else if (eventType.equals(XMLStreamReader.CHARACTERS)){
                    out.print(" " + reader.getText() + "<br/>");
                }else if (eventType.equals(XMLStreamReader.ATTRIBUTE)){
                    out.print(" " + reader.getName() + " <br/>");
                }else if (eventType.equals(XMLStreamReader.END_ELEMENT)){
                    out.print(" " + reader.getName() + " <br/>");
                }
            }
        } catch (XMLStreamException e){
            e.printStackTrace();
        } finally{

            connection.disconnect();
            reader.close();
        }
    }

这是test.jsp

<?xml version="1.0" encoding="UTF-8" ?>
<%@ page  language="java" contentType="text/xml;  charset=UTF-8" %> 
<response>
  <table><%=request.getParameter("table") %></table>
</response>

但是，结果是

response

table
null
table

response

为什么request.getParameter（“table”）无法获取（或DataOutputStream不发送）数据？

我很困惑。

谢谢大家的帮助。

Answer 1

您不应该使用DataOutputStream.writeUTF，请参阅API

首先，将两个字节写入输出流，就好像writeShort方法一样，给出了要遵循的字节数。该值是实际写出的字节数，而不是字符串的长度。在该长度之后，使用针对该字符的修改的UTF-8编码依次输出该字符串的每个字符。如果没有抛出异常，则写入的计数器将增加写入输出流的总字节数。这至少是两个加上str的长度，最多两个加上str的长度三倍。

也就是说，DataOutputStream.writeUTF写入的内容只能使用DataInputStream.readUTF读取

我建议使用

    OutputStreamWriter w = new OutputStreamWriter(connection.getOuputStream(), "UTF-8");
    w.write(urlParameters);
    w.flush();

DataOutputStream似乎不发送参数

1 个答案: