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How do I send XML message in POST body

Greenhorn

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posted 16 years ago

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Hi,

I am trying to write a test web page with associated servlet (running in Tomcat) to send a test message to a third part servlet (also running in Tomcat).

The third party servlet expects a request in the following format:-

I have written a HTML page that will allow the tester to put in up to 5 parameters (name and value) put a XML message:-

When the form posts to the servlet, all of the parameters are specified in the body, which isnt what the third party servlet wants. So, I placed my own servlet in the path MBProxyTest which could take the request and rebuild it in the correct format and forward it to the third party servlet.

import java.io.IOException;
import javax.servlet.Servlet;
import javax.servlet.ServletContext;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.*;
 
public class MBProxyTest extends HttpServlet implements Servlet {
public MBProxyTest() {
super();
}
 
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
boolean useLocalContext = false;
RequestDispatcher dispatcher = null;
HttpServletRequest newRequest = null;
HttpServletResponse newResponse = null;
 
PrintWriter out = response.getWriter();
 
ServletContext context = getServletContext();
if (context == null) {
out.println("ERROR:Cannot get local context\n");
}
 
ServletContext externalContext = context.getContext("/DisplayParameters"); 
if (externalContext == null) {
out.println("ERROR:Cannot get external context\n");
} else {
dispatcher = externalContext.getRequestDispatcher("/DisplayParameters");
if (dispatcher == null) {
out.println("ERROR:Cannot get dispatcher\n");
}
}
 
dispatcher.forward(request, response);
}
 
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
}

The problem is that I cant work out how to create a new request so that I can pass the correctly formated message to the third party servlet.

Any suggestions?

Alan

Paul Clapham

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posted 16 years ago

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You would do it exactly the same way you would do it if your code weren't in a servlet. In other words, servlets have nothing to help you with the task.

If you want to write your own code, you can use a URLConnection object; see Sun's tutorial for more information. But you might find it easier to use Apache's HttpClient package to take care of the HTTP details for you.

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Bear Bibeault

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posted 16 years ago

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+1 on the use of HttpClient. I'm using it to send RESTful requests to a web service I'm setting up which expects XML. It gives you a fine level of control over the content and format of the request.

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Alan Campbell

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posted 16 years ago

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Thanks for replying.

I had thought about creating a new connection but thought that using forward (servlet to servlet) might be more efficient from a connectivity point of view (not having to go through the tcp/ip, http connectiong 'thing').

I am rapidly coming to the conclusion it is not possible to create a new request object 'on the fly' and that the only way would be to create a brand new connection. Is this a correct conclusion?

Alan

Bear Bibeault

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posted 16 years ago

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What's the relationship between the sender and receiver? If they're not in the same web application, a forward is out of the question.

If the receiving server is remote, you need to create a new request to it. How could it possibly have anything to do with the current request on a different server?

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Alan Campbell

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posted 16 years ago

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Originally posted by Bear Bibeault:
What's the relationship between the sender and receiver? If they're not in the same web application, a forward is out of the question.

If the receiving server is remote, you need to create a new request to it. How could it possibly have anything to do with the current request on a different server?

Really? I have to admit, I am new to working with servlets (been doing it 3 days now!), but the code that I posted above (the MBProxyTest servlet) calls the DisplayParameters servlet. Both of these servlets run on the same server and in the same instance of Tomcat, but in different contexts ( had to switch this on in Tomcat, by default it was disabled - crossContext=true). They are seperate web applications. It works in that MBProxyTest can successfully forward to DisplayParameters, which displays the parameters that were entered in the HTML form.
[ November 26, 2008: Message edited by: Alan Campbell ]

Bear Bibeault

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posted 16 years ago

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Will it always be true that they apps reside in the same instance? A forward, even a cross-context forward cannot span servers.

In any case, it's moot here because you need to generate a new request to satisfy the expected requirements of the web service.

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Alan Campbell

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posted 16 years ago

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Originally posted by Bear Bibeault:
Will it always be true that they apps reside in the same instance? A forward, even a cross-context forward cannot span servers.

Yes, this will always be the case.

In any case, it's moot here because you need to generate a new request to satisfy the expected requirements of the web service.

So, does that mean that its not possible to create a new request object?
[ November 26, 2008: Message edited by: Alan Campbell ]

Paul Clapham

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posted 16 years ago

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Originally posted by Alan Campbell:
I am rapidly coming to the conclusion it is not possible to create a new request object 'on the fly' and that the only way would be to create a brand new connection. Is this a correct conclusion?

There's been a lot of conversation since you posted this but I'm surprised you haven't realized that the answer is:

YES.

Alan Campbell

Greenhorn

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posted 16 years ago

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Originally posted by Paul Clapham:
There's been a lot of conversation since you posted this but I'm surprised you haven't realized that the answer is:

YES.

There may have been a lot of conversation but no one actually said that I could or couldnt do it. I just wanted clarification.

Thank you both for your time and patience.

Alan

Amol Nayak

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posted 16 years ago

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You can also construct the xml using javascript using the values in the form you want to submit. Then use something like XMLHttpRequest to submit you xml to the servlet (the third party servlet).
or as Paul and Bear suggested, submit the request to your servlet as a normal form. Get the form fields, construct the xml using maybe the DOM Api of java, create a new request using say HttpClient and post the xml generated in this servlet to the third party servlet. You do this exactly the same way you do in a stand alone core java application.

Alan Campbell

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posted 16 years ago

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I managed to get it to work by creating a wrapper around the request object and modifying the values that way. I got the idea from another post in this forum.

I have posted the code below in case anyone else is looking to do something similar (sorry if its a bit of a long post).

This is my HTML page:-

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<HTML>
<HEAD>
<LINK href="theme/Master.css" rel="stylesheet" type="text/css">
<TITLE>WMB Proxy Servlet Test Message Poster</TITLE>
</HEAD>
<FORM METHOD="POST" ACTION="/ServletTest/ServletTest">
<table border="0" cellpadding="0" cellspacing="0" style="border-collapse: collapse" bordercolor="#111111" width="100%" id="AutoNumber1">
  <tr>
    <td width="150%" align="center" colspan="3"><b>
    <font face="Verdana" size="5">Servlet Test</font></b></td>
  </tr>
  <tr>
    <td width="16%" align="left"> </td>
    <td width="134%" align="left" colspan="2"> </td>
  </tr>
  <tr>
    <td width="16%" align="left"><font face="Verdana" size="2">Servlet</font></td>
    <td width="134%" align="left" colspan="2"><font face="Verdana">
    <INPUT TYPE="TEXT" NAME="ServletName" size="94"></font></td>
  </tr>
  <tr>
    <td width="16%" align="left"> </td>
    <td width="38%" align="left"> </td>
    <td width="96%" align="left"> </td>
  </tr>
  <tr>
    <td width="16%" align="left"> </td>
    <td width="38%" align="left"><font face="Verdana" size="2">Name</font></td>
    <td width="96%" align="left"><font face="Verdana" size="2">Value</font></td>
  </tr>
  <tr>
    <td width="16%" align="left"><font face="Verdana" size="2">Parameter 1</font></td>
    <td width="38%" align="left"><font face="Verdana">
    <INPUT TYPE="TEXT" NAME="ParamName1" size="33"></font></td>
    <td width="96%" align="left"><font face="Verdana">
    <INPUT TYPE="TEXT" NAME="ParamValue1" size="57"></font></td>
  </tr>
  <tr>
    <td width="16%" align="left"><font face="Verdana" size="2">Parameter 2</font></td>
    <td width="38%" align="left"><font face="Verdana">
    <INPUT TYPE="TEXT" NAME="ParamName2" size="33"></font></td>
    <td width="96%" align="left"><font face="Verdana">
    <INPUT TYPE="TEXT" NAME="ParamValue2" size="57"></font></td>
  </tr>
  <tr>
    <td width="16%" align="left"><font face="Verdana" size="2">Parameter 3</font></td>
    <td width="38%" align="left"><font face="Verdana">
    <INPUT TYPE="TEXT" NAME="ParamName3" size="33"></font></td>
    <td width="96%" align="left"><font face="Verdana">
    <INPUT TYPE="TEXT" NAME="ParamValue3" size="57"></font></td>
  </tr>
  <tr>
    <td width="16%" align="left"><font face="Verdana" size="2">Parameter 4</font></td>
    <td width="38%" align="left"><font face="Verdana">
    <INPUT TYPE="TEXT" NAME="ParamName4" size="33"></font></td>
    <td width="96%" align="left"><font face="Verdana">
    <INPUT TYPE="TEXT" NAME="ParamValue4" size="57"></font></td>
  </tr>
  <tr>
    <td width="16%" align="left"><font face="Verdana" size="2">Parameter 5</font></td>
    <td width="38%" align="left"><font face="Verdana">
    <INPUT TYPE="TEXT" NAME="ParamName5" size="33"></font></td>
    <td width="96%" align="left"><font face="Verdana">
    <INPUT TYPE="TEXT" NAME="ParamValue5" size="57"></font></td>
  </tr>
</table>
<P>
 <table border="0" cellpadding="0" cellspacing="0" style="border-collapse: collapse" bordercolor="#111111" width="100%" id="AutoNumber2">
  <tr>
    <td width="16%">
    <p align="left"><font face="Verdana" size="2">Test message</font></td>
    <td width="84%">
<p align="left">
<font face="Verdana">
<TEXTAREA NAME="TestMessage" ROWS=17 COLS=90>
</TEXTAREA></font></td>
  </tr>
</table>
<P align="left">
<font face="Verdana">
<INPUT TYPE=SUBMIT NAME="SendTest" VALUE="Send Test"><font size="2"> </font>
</font>
</FORM>
</BODY>
</HTML>

This is my servlet code:-

import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
 
public class ServletTest extends HttpServlet implements Servlet {
public ServletTest() {
super();
}
 
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
RequestDispatcher dispatcher = null;
ServletTestReqWrapper requestWrapper = null;
String paramTestMessage = null;
String extServlet = null;
String extServletContext = null;
String extServletName = null;
    StringBuffer parameterStringBuffer = new StringBuffer();
String parameterName = null;
String parameterValue = null;
int seperatorPos = 0;
int loopCounter = 0;
 
// Get the name of the servlet, including its context
extServlet = request.getParameter("ServletName");
if (extServlet == null) {
throw new ServletException("Servlet parameter not found");
}
 
seperatorPos = extServlet.indexOf('/');
if (seperatorPos == -1) {
throw new ServletException("Invalid servlet name - it must start with /");
} else {
seperatorPos = extServlet.indexOf('/', (seperatorPos + 1));
if (seperatorPos == -1) {
throw new ServletException("Invalid servlet name - it must be conext/servlet");
}
}
 
extServletContext = extServlet.substring(0, seperatorPos);
extServletName = extServlet.substring(seperatorPos);

// Get each of the parameters (max of 5) and build a parameter string.
for (loopCounter = 0; loopCounter < 6; loopCounter = loopCounter + 1) {
parameterName = request.getParameter(("ParamName" + loopCounter));
if (parameterName != null) {
if (parameterName.length() > 0) {
parameterValue = request.getParameter(("ParamValue" + loopCounter));
if (parameterValue != null) {
if (parameterStringBuffer.length() > 0) {
parameterStringBuffer.append("&");
}
 
parameterStringBuffer.append(parameterName);
parameterStringBuffer.append("=");
parameterStringBuffer.append(parameterValue);
}
}
}
}
 
// Get the test message.
paramTestMessage = request.getParameter("TestMessage");
 
// Create a request wrapper so that we can modify the values of the
// request object.
HttpServletRequest httpServletRequest = (HttpServletRequest)request;
try {            
requestWrapper = new ServletTestReqWrapper(httpServletRequest);
} catch (IOException ex) {
throw new ServletException("Unable to create request wrapper", ex);
}
 
// Override these values in the wrapper request.
requestWrapper.setPayload(paramTestMessage);
requestWrapper.setQueryString(parameterStringBuffer.toString());
 
// Get our local context.
ServletContext context = getServletContext();
if (context == null) {
throw new ServletException("Cannot get local context");
}
 
// get the context of the external servlet.
ServletContext externalContext = context.getContext(extServletContext); 
if (externalContext == null) {
throw new ServletException("Cannot get external context");
} else {
// Get the dispatcher for the external context
dispatcher = externalContext.getRequestDispatcher(extServletName);
if (dispatcher == null) {
throw new ServletException("Cannot get dispatcher");
}
}
 
// Forward this new wrapper request to the external servlet.
dispatcher.forward(requestWrapper, response);
}
 
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
}

And this is my wrapper code:-

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
 
public class ServletTestReqWrapper extends HttpServletRequestWrapper {

private String wrapperXmlPayload;
private String wrapperQueryString;
 
public ServletTestReqWrapper (HttpServletRequest request) throws IOException {
 
super(request);
 
// read the original payload into the xmlPayload variable
StringBuffer stringBuffer = new StringBuffer();
BufferedReader bufferedReader = null;
 
try {
// read the payload into the StringBuilder
InputStream inputStream = request.getInputStream();
if (inputStream != null) {
bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
 
char[] charBuffer = new char[128];
int bytesRead = -1;
 
while ((bytesRead = bufferedReader.read(charBuffer)) > 0) {
stringBuffer.append(charBuffer, 0, bytesRead);
}
} else {
// make an empty string because there is no payload
stringBuffer.append("");
}
} catch (IOException ex) {
throw ex;
} finally {
if (bufferedReader != null) {
try {
bufferedReader.close();
} catch (IOException iox) {
// ignore
}
}
}
 
wrapperXmlPayload = stringBuffer.toString();

wrapperQueryString = request.getQueryString();
}

/**
 * Override of the getInputStream() method which returns an InputStream that reads from the
 * stored XML payload string instead of from the request's actual InputStream.
 */
//@Override
public ServletInputStream getInputStream () throws IOException {
final ByteArrayInputStream byteArrayInputStream = new ByteArrayInputStream(wrapperXmlPayload.getBytes());
ServletInputStream inputStream = new ServletInputStream() {
public int read () throws IOException {
return byteArrayInputStream.read();
}
};

return inputStream;
}
 
/**
 * Override of the getQueryString() method to return the value in the local variable.
 */
    public String getQueryString() {
    return wrapperQueryString;
    }
 
/**
 * New setPayload() method which sets the local variables value.
 */
public boolean setPayload(String newPayload) throws ServletException {
wrapperXmlPayload = newPayload;
 
return true;
}
 
/**
 * New setQueryString() method which sets the local variables value.
 */
public boolean setQueryString(String newQueryString) throws ServletException {
wrapperQueryString = newQueryString;
 
return true;
}
}

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