Java HTTP Servlet to be used as a bridge between a Web APP and Oracle BI Server when using OBIEE SOAP API for integration scenarios.

OBIEEHttpServletBridge.java

package br.net.rafaeltuelho.servlets;

import java.io.DataOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.UnsupportedEncodingException;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLEncoder;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;

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

import org.apache.log4j.Logger;

/**
 * Servlet implementation class OBIEEBridge
 */
public class OBIEEBridge extends HttpServlet {

	private static final long serialVersionUID = 1L;
	private static Logger logger = org.apache.log4j.Logger
			.getLogger(OBIEEBridge.class);

	/**
	 * @see HttpServlet#HttpServlet()
	 */
	public OBIEEBridge() {
		super();
	}

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse
	 *      response)
	 */
	protected void doGet(HttpServletRequest request,
			HttpServletResponse response) throws ServletException, IOException {
		logger.info("doGet");

		try {
			this.processRequest(request, response);
		} catch (Exception e) {
			logger.error("Servlet Error: ", e);
			throw new ServletException(e);
		}
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
	 *      response)
	 */
	protected void doPost(HttpServletRequest request,
			HttpServletResponse response) throws ServletException, IOException {

		logger.info("doPost");
		try {
			this.processRequest(request, response);
		} catch (Exception e) {
			logger.error("Servlet Error: ", e);
			throw new ServletException(e);
		}
	}

	protected void processRequest(HttpServletRequest request,
			HttpServletResponse response) throws ServletException, IOException {
		
		HttpURLConnection urlCon = forwardRequest(request);
		forwardResponse(response, urlCon);
	}

	@SuppressWarnings("unchecked")
	private String decodeURL(HttpServletRequest request) {

		StringBuffer bufURL = new StringBuffer("");
		
		Map<String, String[]> params = request.getParameterMap();
		logger.debug("Request param is: " + params.toString());

		String[] arrURL = params.get("RedirectURL");
		String strURL = arrURL == null || arrURL.length == 0 ? null : arrURL[0];		
		bufURL.append(strURL);

		logger.info("URL is: " + strURL);

		int nQIndex = strURL.lastIndexOf('?');

		if (params != null && !params.isEmpty()) {
			bufURL.append(((nQIndex >= 0) ? "&" : "?"));
			Set<String> keys = params.keySet();
			Iterator<String> it = keys.iterator();
			while (it.hasNext()) {
				try {
					String strKey = it.next();
					
					if (strKey.equalsIgnoreCase("RedirectURL")){
						logger.debug("skipping [RedirectURL] key from map parameters...");
						continue;
					}
					
					String strEncodedKey = URLEncoder.encode(strKey, "UTF-8");
						
					String[] paramValues = params.get(strKey);
					for (String paramValue : paramValues) {
						bufURL.append(strEncodedKey);
						bufURL.append("=");
						bufURL.append(URLEncoder.encode(paramValue, "UTF-8"));
						bufURL.append("&");
					}
				} catch (UnsupportedEncodingException e) {
					e.printStackTrace();
				}
			}
			
			bufURL.deleteCharAt(bufURL.length() - 1);
		}

		return bufURL.toString();
	}

	@SuppressWarnings("unchecked")
	private HttpURLConnection forwardRequest(HttpServletRequest request)
			throws IOException {
		logger.info(">>> forwardRequest >>>");
		
		String strURL = decodeURL(request);
		logger.info("\t decodeURL returned: " + strURL);
		
		String[] arrURL = strURL.split("&", 2);
		String baseURL = arrURL[0];

		URL url = new URL(baseURL);
		HttpURLConnection con = (HttpURLConnection) url.openConnection();
		logger.info("\t Connection opened  OK");
		
		String strMethod = request.getMethod();
		con.setRequestMethod(strMethod);

		Enumeration<String> en = request.getHeaderNames();
		String strHeader;
		while (en.hasMoreElements()) {
			strHeader = en.nextElement();
			
			String strHeaderValue = request.getHeader(strHeader);
			logger.debug("\t Set [request] header " + strHeader + "=" + strHeaderValue);
			con.setRequestProperty(strHeader, strHeaderValue);
		}

		// is not a HTTP GET request
		if (strMethod.compareTo("GET") != 0) {
			logger.info("\t Try to copy request body and send within a [" + strMethod + 
					"] request to the target ["+
					con.getURL().getHost() + "] Server");
			
			con.setDoOutput(true);
			con.setDoInput(true);
			con.setUseCaches(false);
			
			DataOutputStream forwardStream = new DataOutputStream(con.getOutputStream());
			
			try {
				String urlParameters = arrURL[1];
				forwardStream.writeBytes(urlParameters);
				forwardStream.flush();
			} finally {
				forwardStream.close();
			}
		}

		return con;
	}

	private void forwardResponse(HttpServletResponse response, HttpURLConnection con)
			throws IOException {
		
		logger.info("<<< forwardResponse <<<");
		
		int nContentLen = -1;
		String strKey;
		String strValue;
		
		try {
			
			response.setStatus(con.getResponseCode());
			
			for (int i = 1; true; ++i) {
				strKey = con.getHeaderFieldKey(i);
				strValue = con.getHeaderField(i);
				
				if (strKey == null){
					break;
				}
				
				if (strKey.equals("Content-Length")) {
					nContentLen = Integer.parseInt(con.getHeaderField(i));
					continue;
				}
				
				if (strKey.equalsIgnoreCase("Connection")
						|| strKey.equalsIgnoreCase("Server")
						|| strKey.equalsIgnoreCase("Transfer-Encoding")
						|| strKey.equalsIgnoreCase("Content-Length")){
					continue; // skip certain headers
				}
				
				
				if(strKey.equalsIgnoreCase("Set-Cookie")){
					String[] cookieStr1 = strValue.split(";");
					String[] cookieStr2 = cookieStr1[0].split("=");
//					String[] cookieStr3 = cookieStr1[1].split("=");
					
					/* Change the Set-Cookie HTTP Header to remove the 'path' attribute. 
					   Thus the browser can accept the ORA_BIPS_NQID cookie from Oracle BI Server */

					Cookie c =  new Cookie(cookieStr2[0], cookieStr2[1]);
					c.setPath("/");
					response.addCookie(c);
					
					logger.info("\t Add COOKIE \n\t" +
							c.getName() + "\n\t\t" + 
							"value: "   + c.getValue() + "\n\t\t" + 
							"path: "    + c.getPath()  + "\n\t\t" +
							"domain: "  + c.getDomain());
				}
				else{
					response.setHeader(strKey, strValue);
					
					logger.info("\t Set [response] header " + strKey + " = " + strValue);
				}
				
			}

			copyStreams(con.getInputStream(), response.getOutputStream(),
					nContentLen);
			
		} finally {
			response.getOutputStream().close();
			con.getInputStream().close();
		}
	}

	private void copyStreams(InputStream inputStream, OutputStream forwardStream,
			int nContentLen) throws IOException {
		
		logger.debug("copyStreams called nContentLen=" + nContentLen);
		
		byte[] buf = new byte[1024];
		int nCount = 0;
		int nBytesToRead = 1024;
		int nTotalCount = 0;
		
		do {
			if (nContentLen != -1)
				nBytesToRead = nContentLen - nTotalCount > 1024 ? 1024 : nContentLen - nTotalCount;
				
			if (nBytesToRead == 0)
				break;
			
			logger.debug("copyStreams. About to call inputStream.read " + nBytesToRead);
			
			// try to read some bytes from src stream
			nCount = inputStream.read(buf, 0, nBytesToRead);
			
			logger.debug("copyStreams.read returned  " + nCount);
			
			if (nCount < 0)
				break;
			
			nTotalCount += nCount;
			
			logger.debug("copyStreams. About to call forwardStream.write " + nCount);
			
			// try to write some bytes in target stream
			forwardStream.write(buf, 0, nCount);
			
			logger.debug("copyStreams. write  done");
		} while (true);
	}

}