Embeddding an Apache Axis application in Tomcat

One of the applications I’ve been heading up at my 8-to-5 needed a SOAP API that fronted a Java application deployed on Tomcat. If you’ve spent any time with Axis you know that it’s not the simplest thing to deal with; in fact it’s downright complex if you want do anything more than the simplest thing using SOAP. The simplest? Write your source code, rename the .java file to have a .jws extension and then copy the file into a public directory inside your servlet container (see ‘Deploy a Java Class as a Web Service’). Easy. But this method leaves alot to be desired: you can’t use packages in the source code and the code is compiled at runtime which means you don’t find out about compilation errors until after deployment (one way around this would be to first compile the .java file to make sure that it works and then use Ant to copy / rename the .java file to a .jws) and you can’t specify custom type mappings, among other things. Lucky for you, the jws method isn’t the only way you can do it.

The next two options give you flexibility with the additional cost of complexity. The first method is well covered in the documentation: Axis comes packaged with a web application that you can deploy to your servlet container and then add your custom services using a remote administration client also provided with the war file that you deploy. The downside (at least in my environment) is that this means you now have to maintain and deploy two separate applications: my Java based web application would be deployed to Tomcat and then the same business logic would be deployed to the Axis engine running inside of Tomcat. I felt that it would be simpler to maintain to instead deploy the web application and the SOAP application together as one application in one war file. That of course, is not well documented (in fact other than a PDF file that’s part of the ‘Java Development with Ant‘ written by Erik Hatcher, there is no mention of deploying your web application alongside an Axis application without using the Axis AdminClient). Hence the article you’re reading now.

step 1: setup application / dependent libraries: I’ll make the assumption that you already have a web application that you want to expose SOAP webservices with which means you probably have a file structure that looks like something like this:


You’ll need to add the following libraries to your WEB-INF/lib directory:
* axis.jar
* axis-ant.jar
* jaxrpc.jar
* wsdl4j.jar
* commons-logging.jar
* commons-discovery.jar
* saaj.jar

If you don’t, you can download the sample application I wrote that exposes a single hello world webservice.

Alright, so either you’ve downloaded the sample application or you’ve got your own application and you’ve added the above libraries to your WEB-INF/lib directory. Now you’re ready to write some script to expose your existing classes.

step 2: use WSDL2Java / Java2WSDL to generate the server side wrapper & deployment descriptors for the classes you want to expose. Write a interface:

package net.cephas.soap;
public interface HelloWorld extends java.rmi.Remote {
  public java.lang.String sayHello(java.lang.String in0)
    throws java.rmi.RemoteException;

and then a corresponding implementation which should be named $InterfaceName + SoapBindingImpl

package net.cephas.soap;
import java.rmi.RemoteException;
public class HelloworldSoapBindingImpl implements HelloWorld {
  public String sayHello(String name) throws RemoteException {
    return "hello " + name;

Next, you can use Ant (but you could easily run this from the command line as well) to create the WSDL and generate the server side wrapper & deployment descriptors. You’ll need to define two tasks in Ant:

<taskdef name="axis-java2wsdl" classname="org.apache.axis.tools.ant.wsdl.Java2WsdlAntTask">
  <classpath refid="compile.classpath" />
<taskdef name="axis-wsdl2java" classname="org.apache.axis.tools.ant.wsdl.Wsdl2javaAntTask">
  <classpath refid="compile.classpath" />

and then you can generate the WSDL:


and generate the server side wrappers:


Copy the generated web service deployment descriptor (deploy.wsdd) file to WEB-INF/server-config.wsdd:

<copy file="generated/net/cephas/soap/deploy.wsdd"
  tofile="WEB-INF/server-config.wsdd" />

and the *SoapBindingSkeleton.java file to your source tree:

<copy todir="src/net/cephas/soap" includeEmptyDirs="no">
  <fileset dir="generated/net/cephas/soap">
    <include name="*SoapBindingSkeleton.java" />

Finally, compile your source and either jar it up to the WEB-INF/lib directory or deploy the compiled classes to the WEB-INF/classes directory.

step 3: configure web.xml with the appropriate servlet mappings. The last thing you need to do is to map a resource path in your application to Axis, you accomplish this by adding a servlet and servlet-mapping element to your web.xml:

  <display-name>Apache-Axis Servlet</display-name>

You can see that I’ve selected ‘/soap/’ as the resource path which in combination with the server-config.wsdd means that I’ll invoke the SOAP web service using a URL like this:


where embeddedaxis is the name I’ve the sample application. It will probably be different for your application.

Phew! That’s an awful lot of scripting and configuration to deploy hello world, but at least now you don’t have to rely on .jws files or deploying your application separately from the SOAP service. If you’re trying to do the same thing and something you read above doesn’t make sense, ping me.

Download embeddedaxis.zip.

Java, Collections and Multimap

I was in an interview recently and was asked a question which I thought the interviewer called an ‘atagram’, but I think it was actually an anagram. He asked how you could find the largest word in a dictionary where subtracting one letter results in another word (ie: ‘beat’ minus ‘e’ could be ‘tab’). I didn’t come up with an suitable answer during the interview, but during some unrelated reading this week I came across the question and the answer: multimap. Scroll down to the bottom of this page and start reading when you get to multimaps. The trick is that a multimap allows one key to map to multiple values and by alphabetizing each word in the dictionary and then placing the word in the map keyed by the alphabetized word, you can easily find all the available words which result from word minus letter.

Links: 8-15-2005

XML characters, smart quotes and Apache XML-RPC

I’ve been eating my own dogfood with the deliciousposter project (as you can see from my daily links). A couple days ago I posted a some links to del.icio.us and expected them to show up automatically the next day… except they didn’t. I traced it down to an errant smart quote that I copied from the Internet Alchemy Talis, Web 2.0 and All That post, which caused the Apache XML-RPC library to throw this error:

java.io.IOException: Invalid character data corresponding to XML entity ’

I worked under the assumption that the smart quote was an invalid XML character for quite awhile, but it looks like it actually is according to the XML 1.1 specification, the following characters are allowed in an XML document:

#x9 | #xA | #xD | [#x20-#xD7FF] | [#xE000-#xFFFD] | [#x10000-#x10FFFF]

I then checked the source code for the XmlWriter which has this method for writing character data:

if (c < 0x20 || c > 0xff) {
  // Though the XML-RPC spec allows any ASCII
  // characters except '<' and '&', the XML spec
  // does not allow this range of characters,
  // resulting in a parse error from most XML
  // parsers.
  throw new XmlRpcClientException("Invalid character data " +
  "corresponding to XML entity &#" +
  String.valueOf((int) c) + ';', null);
} else ..

which turns out to be a tad aggressive. It also turns out that the above code snippet and the version of the Apache XML-RPC library I was using are out of date. The chardata(String text) has been updated in the latest version of the Apache XMl-RPC library to include a new method called isValidXMLChar(char c) which is much more lenient:

if (c == '\n') return true;
if (c == '\r') return true;
if (c == '\t') return true;
if (c
and not coincidentally, is compliant with the specification.

I'll be updating deliciousposter to use the latest version of the Apache XML-RPC library soon. In the meantime, if you're using the Apache XML-RPC library, you should probably download the latest version to take advantage of the new XML character validation method.

Links: 8-9-2005