使用HTTPURLConnection从HTTP Java客户端向Servlet发送XML数据时出现问题

Question

我有一个独立的Java客户端使用httpURLconnection类将xml数据发送到http servlet，但是数据以不可打印的字符格式显示。

为了进行模拟，我一直在尝试发送简单的字符串，但是它仍然以不可打印的格式出现。

我已经编写了以下客户端代码来与Servlet进行通信，

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.net.HttpURLConnection;
import java.net.ProtocolException;
import java.net.URL;

public class HttpClient implements IClient {

    private static IClient client = null;

    private HttpURLConnection httpConn = null;

    private OutputStream output = null;

    private InputStream input = null;

    private OutputStreamWriter out = null;

    private HttpClient() {
    }

    public static IClient getHttpClient() {
        if (client == null) {
            client = new HttpClient();
        }
        return client;
    }

    @Override
    public void connect(String urlString) throws IOException {
        URL url = new URL(urlString);
        httpConn = (HttpURLConnection) url.openConnection();
        initConnection();
        httpConn.connect();
        output = httpConn.getOutputStream();
        input = httpConn.getInputStream();
        System.out.println("Connection Response:" + httpConn.getResponseCode());
    }

    @Override
    public void sendFile(File file) throws IOException {
        // BufferedOutputStream bos = new BufferedOutputStream(output);
        // InputStream fis = new FileInputStream(file);
        // int bytesRead = 0;
        // byte[] buffer = new byte[8192];
        // while ((bytesRead = fis.read(buffer, 0, 8192)) != -1) {
        // bos.write(buffer, 0, bytesRead);
        // System.out.println("write:"+buffer);
        // }
        // bos.close();
        // fis.close();

        OutputStreamWriter out = new OutputStreamWriter(output, "UTF-16");
        out.write("test me");
    }

    @Override
    public boolean isConnected() {
        return httpConn != null ? true : false;
    }

    @Override
    public void close() {
        httpConn.disconnect();
    }

    private void initConnection() throws ProtocolException {
        httpConn.setDoOutput(true);
        httpConn.setDoInput(true);
        httpConn.setRequestMethod("POST");
        httpConn.setUseCaches(false);
        httpConn.setRequestProperty("Content-Type",
                "text/xml; charset=\"UTF-16\"");
        httpConn.setRequestProperty("Connection", "Keep-Alive");

    }

    private static byte[] getBytesFromFile(File file) throws IOException {

        InputStream is = new FileInputStream(file);
        System.out.println("\nDEBUG: FileInputStream is " + file);

        // Get the size of the file
        long length = file.length();
        System.out.println("DEBUG: Length of " + file + " is " + length + "\n");

        /*
         * You cannot create an array using a long type. It needs to be an int
         * type. Before converting to an int type, check to ensure that file is
         * not loarger than Integer.MAX_VALUE;
         */
        if (length > Integer.MAX_VALUE) {
            System.out.println("File is too large to process");
            return null;
        }

        // Create the byte array to hold the data
        byte[] bytes = new byte[(int) length];

        // Read in the bytes
        int offset = 0;
        int numRead = 0;
        while ((offset < bytes.length)
                && ((numRead = is.read(bytes, offset, bytes.length - offset)) >= 0)) {

            offset += numRead;

        }

        // Ensure all the bytes have been read in
        if (offset < bytes.length) {
            throw new IOException("Could not completely read file "
                    + file.getName());
        }

        return bytes;

    }

}

并在下面给出了servlet代码，

import java.io.BufferedInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStream;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class XMLServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        doPost(req, resp);
    }

    protected void doPost(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        System.out.println("=========inside doPost=========");
//      BufferedInputStream bis = new BufferedInputStream(req.getInputStream());
//      OutputStream fos = new FileOutputStream("test.xml");
//      int bytesRead = 0;
//      byte[] buffer = new byte[8192];
//      while ((bytesRead = bis.read(buffer, 0, 8192)) != -1) {
//          System.out.println("read:"+buffer);
//          fos.write(buffer, 0, bytesRead);
//      }
//      fos.close();
//      bis.close();
//      

        req.setCharacterEncoding("UTF-16");
        InputStreamReader isr = new InputStreamReader(req.getInputStream(),"UTF-16");
        char[] data = new char[10];
        isr.read(data);
        System.out.println(data);
        for (char c : data) {
            System.out.println(c);
        }
    }

}

请任何帮助我摆脱这个问题。

Answer 1

我认为您太复杂了。 我只写了类似的东西，它可以接收任何文件并将其通过HTTP传输到servlet。 只需记住：所有数据都是二进制（包括文本文件）-周期。 由给定的应用程序来解释该二进制数据。 例如，notepad.exe仅读取二进制数据集并尝试使用ASCII标准对其进行格式化。 因此，只需使用原始流读取文件，将连接的mime类型设置为application / octet-stream，然后通过“ PUT”方法将其发送即可。 Servlet代码应使用请求中的原始InputStream读取文件，并在其空间中创建相应的文件。

从客户端代码：

URL url = new URL(urlString);
HttpURLConnection cnx = (HttpURLConnection)url.openConnection();
cnx.setRequestMethod("PUT");
cnx.setRequestProperty("Content-Type", "application/octet-stream");
// optional request property
cnx.setRequestProperty("filename", filename);
cnx.setDoOutput(true);
cnx.connect();
BufferedInputStream fileIn = 
       new BufferedInputStream(new FileInputStream(fileName), BUFFER_SIZE);
BufferedOutputStream out = 
       new BufferedOutputStream(cnx.getOutputStream(), BUFFER_SIZE);
byte[] bytes = new byte[BUFFER_SIZE];
int bytesRead;
while((bytesRead = fileIn.read(bytes)) != -1){
   out.write(bytes, 0, bytesRead);
}

而已。

现在是servlet代码。

public void doPut(HttpServletRequest request, HttpServletResponse response){
    String filename = (String)request.getHeader("filename");
    StringBuilder fullPath = new StringBuilder(100);
    ServletContext ctxt = getServletContext();
    fullPath.append(ctxt.getRealPath(""))
      .append("uploads\\").append(filename);
    File f = new File(fullPath.toString());
    f.createNewFile();
    InputStream in = request.getInputStream();
    BufferedOutputStream fileOut = 
        new BufferedOutputStream(new FileOutputStream(f));
    byte[] bytes = new byte[BUFFER_SIZE];
    int bytesRead;
    while((bytesRead = in.read(bytes)) != -1){
       fileOut.write(bytes, 0, bytesRead);
    }
    fileOut.flush();
    fileOut.close();
    response.setStatus(HttpServletResponse.SC_CREATED);   
}

Answer 2

使用http方法将文件上传到服务器的方式主要有两种：

1. 使用PUT方法上传文件。 这使您可以一次将一个文件放到服务器上。 PUT方法易于实现，但是您不能使用PUT方法从html表单上载文件（例如，在Web浏览器中上载表单）。

2. 使用POST方法上传文件。 这比较复杂，但是大多数网站都使用它来将文件上传到服务器上。 您可以针对每个请求上传多个文件。 这就是我要谈的。

注意： GET不用于文件上传，除非您以某种方式对其进行编码。

使用URLConnection上传文件不是直接的，需要您以“ 多部分形式 ”准备数据。 当然，您不应该自己做。 有许多库可以为您解决这个问题，例如HttpClient 。 如果您真的想使用URLConnection ，我将参考前面的问题“ 如何使用java.net.URLConnection来触发和处理HTTP请求 ”

以下是使用HttpClient上传文件的代码。 它从HttpClient示例代码简化。

import java.io.File;


import org.apache.commons.httpclient.HttpClient;
import org.apache.commons.httpclient.HttpStatus;
import org.apache.commons.httpclient.methods.PostMethod;
import org.apache.commons.httpclient.methods.multipart.FilePart;
import org.apache.commons.httpclient.methods.multipart.MultipartRequestEntity;
import org.apache.commons.httpclient.methods.multipart.Part;
import org.apache.commons.httpclient.params.HttpMethodParams;

public class MultipartFileUploadApp {

    public static void main(String[] args) {
        String targetURL = "http://localhost:8080/yourserver/upload";
        File targetFile = new File("/path/to/your/file.txt");

        PostMethod filePost = new PostMethod(targetURL);

        filePost.getParams().setBooleanParameter(HttpMethodParams.USE_EXPECT_CONTINUE, false);

        try {

            System.out.println("Uploading " + targetFile.getName() + " to " + targetURL);

            // add more parts you want to upload multiple files.
            Part[] parts = {new FilePart(targetFile.getName(), targetFile)};

            filePost.setRequestEntity(new MultipartRequestEntity(parts, filePost.getParams()));

            HttpClient client = new HttpClient();
            client.getHttpConnectionManager().getParams().setConnectionTimeout(5000);

            int status = client.executeMethod(filePost);

            if (status == HttpStatus.SC_OK) {
                System.out.println("Upload complete, response=" + filePost.getResponseBodyAsString());
            } else {
                System.out.println("Upload failed, response=" + HttpStatus.getStatusText(status));
            }
        } catch (Exception ex) {
            System.out.println("Error: " + ex.getMessage());
            ex.printStackTrace();
        } finally {
            filePost.releaseConnection();
        }


    }
}

对于服务器端，您必须解析多部分表单请求。 当然，存在可以为您执行此操作的库。 这是我正在使用的片段

import java.io.File;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Iterator;
import java.util.List;

import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.FileUploadException;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;

public class CommonsFileUploadServlet extends HttpServlet {

    private static final String TMP_DIR_PATH = "c:\\tmp";
    private File tmpDir;
    private static final String DESTINATION_DIR_PATH = "c:\\tmp\\files";
    private File destinationDir;

    public void init(ServletConfig config) throws ServletException {
        super.init(config);
        tmpDir = new File(TMP_DIR_PATH);
        if (!tmpDir.isDirectory()) {
            throw new ServletException(TMP_DIR_PATH + " is not a directory");
        }
        //String realPath = getServletContext().getRealPath(DESTINATION_DIR_PATH);
        destinationDir = new File(DESTINATION_DIR_PATH);
        if (!destinationDir.isDirectory()) {
            throw new ServletException(DESTINATION_DIR_PATH + " is not a directory");
        }

    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        PrintWriter out = response.getWriter();
        response.setContentType("text/plain");
        out.println("<h1>Servlet File Upload Example using Commons File Upload</h1>");
        out.println();

        DiskFileItemFactory fileItemFactory = new DiskFileItemFactory();
        /*
         *Set the size threshold, above which content will be stored on disk.
         */
        fileItemFactory.setSizeThreshold(1 * 1024 * 1024); //1 MB
        /*
         * Set the temporary directory to store the uploaded files of size above threshold.
         */
        fileItemFactory.setRepository(tmpDir);

        ServletFileUpload uploadHandler = new ServletFileUpload(fileItemFactory);
        try {
            /*
             * Parse the request
             */
            List items = uploadHandler.parseRequest(request);
            out.println("Count : " + items.size());
            Iterator itr = items.iterator();
            while (itr.hasNext()) {
                FileItem item = (FileItem) itr.next();
                /*
                 * Handle Form Fields.
                 */
                if (item.isFormField()) {
                    out.println("Field = " + item.getFieldName() + ", Value = " + item.getString());
                } else {
                    //Handle Uploaded files.
                    out.println("Field Name = " + item.getFieldName()
                            + ", File Name = " + item.getName()
                            + ", Content type = " + item.getContentType()
                            + ", File Size = " + item.getSize());
                    /*
                     * Write file to the ultimate location.
                     */
                    File file = new File(destinationDir, item.getName());
                    item.write(file);
                }
            }
            out.close();
        } catch (FileUploadException ex) {
            log("Error encountered while parsing the request", ex);
        } catch (Exception ex) {
            log("Error encountered while uploading file", ex);
        }

    }
}

Answer 3

我有一个独立的Java客户端使用httpURLconnection类将xml数据发送到http servlet，但是数据以不可打印的字符格式显示。

我能理解 您以UTF-16的形式发送数据，但是XML文件本身可能未保存在UTF-16中。 您需要使用与保存XML文件相同的字符编码。通常为UTF-8。

为了进行模拟，我一直在尝试发送简单的字符串，但是它仍然以不可打印的格式出现。

我不明白 它应该可以像您在代码中那样很好地工作。 可能您没有正确测试。