Java – WCF Serialization problems with WSDL file created by Java tools

interopjavaserializationwcfwsdl

My team is tasked with getting several in-house developed .NET client applications to connect to some new Java web services. The Java web service is a third party, vendor supplied WSDL file that our team has a limited ability to modify/control…meaning we probably have the power to request our vendor to make slight tweaks to the WSDL, but major changes would probably be either unfeasible or difficult to request.

That said, we are attempting to utilize WCF/.NET 4.0 to generate the .NET proxy class files we need on the client side. The proxy client class file generation process executes without issues.

The problem is when we attempt to use the proxy class file in a client app. I have verified through the web trace tool, Fiddler, that the raw SOAP message request fails to get sent across the wire to the server.

The specific .NET exception message I get when attempting to call the web service method in question, looks like this:

System.InvalidOperationException was unhandled
Message=XmlSerializer attribute System.Xml.Serialization.XmlAttributeAttribute is not valid in baseLanguage. Only XmlElement, XmlArray, XmlArrayItem, XmlAnyAttribute and XmlAnyElement attributes are supported when IsWrapped is true.
Source=System.ServiceModel

When I examine the .NET autogenerated proxy class file, Reference.cs, I noticed that the request and response messages for my web service method looks something like this:

[System.Diagnostics.DebuggerStepThroughAttribute()]
[System.CodeDom.Compiler.GeneratedCodeAttribute("System.ServiceModel", "4.0.0.0")]
[System.ServiceModel.MessageContractAttribute(WrapperName="QueryPBOT_MXWO_OS", WrapperNamespace="http://www.ibm.com/maximo", IsWrapped=true)]
public partial class QueryPBOT_MXWO_OSRequest {

    [System.ServiceModel.MessageBodyMemberAttribute(Namespace="http://www.ibm.com/maximo", Order=0)]
    public ConsoleApplication7.wsMaximo.PBOT_MXWO_OSQueryType PBOT_MXWO_OSQuery;

    [System.ServiceModel.MessageBodyMemberAttribute(Namespace="http://www.ibm.com/maximo", Order=1)]
    [System.Xml.Serialization.XmlAttributeAttribute()]
    public string baseLanguage;

    [System.ServiceModel.MessageBodyMemberAttribute(Namespace="http://www.ibm.com/maximo", Order=2)]
    [System.Xml.Serialization.XmlAttributeAttribute()]
    public string transLanguage;

    [System.ServiceModel.MessageBodyMemberAttribute(Namespace="http://www.ibm.com/maximo", Order=3)]
    [System.Xml.Serialization.XmlAttributeAttribute()]
    public string messageID;

    [System.ServiceModel.MessageBodyMemberAttribute(Namespace="http://www.ibm.com/maximo", Order=4)]
    [System.Xml.Serialization.XmlAttributeAttribute()]
    public string maximoVersion;

    [System.ServiceModel.MessageBodyMemberAttribute(Namespace="http://www.ibm.com/maximo", Order=5)]
    [System.Xml.Serialization.XmlAttributeAttribute()]
    [System.ComponentModel.DefaultValueAttribute(false)]
    public bool uniqueResult;

    [System.ServiceModel.MessageBodyMemberAttribute(Namespace="http://www.ibm.com/maximo", Order=6)]
    [System.Xml.Serialization.XmlAttributeAttribute(DataType="positiveInteger")]
    public string maxItems;

    [System.ServiceModel.MessageBodyMemberAttribute(Namespace="http://www.ibm.com/maximo", Order=7)]
    [System.Xml.Serialization.XmlAttributeAttribute(DataType="integer")]
    [System.ComponentModel.DefaultValueAttribute("0")]
    public string rsStart;

    public QueryPBOT_MXWO_OSRequest() {
    }

    public QueryPBOT_MXWO_OSRequest(ConsoleApplication7.wsMaximo.PBOT_MXWO_OSQueryType PBOT_MXWO_OSQuery, string baseLanguage, string transLanguage, string messageID, string maximoVersion, bool uniqueResult, string maxItems, string rsStart) {
        this.PBOT_MXWO_OSQuery = PBOT_MXWO_OSQuery;
        this.baseLanguage = baseLanguage;
        this.transLanguage = transLanguage;
        this.messageID = messageID;
        this.maximoVersion = maximoVersion;
        this.uniqueResult = uniqueResult;
        this.maxItems = maxItems;
        this.rsStart = rsStart;
    }
}

I know that people reading this post will want to see the actual WSDL file we're trying to consume, but it is quite large, and I'm concerned the sheer size of it would make pinpointing the error quite difficult.

I'm hoping that the autogenerated client proxy file and the .NET exception will help someone recognize this WCF Serialization issue.

We've confirmed from our Java vendor that the style of WSDL they generate is doc-literal. After doing some research on the internet, it appears that WCF, by default. translates WSDL files with doc-literal wrapped, and that this may explain, at least in part, why we're seeing this WCF serialization issue with the WSDL file.

I've discovered, through trial and error, that the following attribute decorator in the proxy class file is the culprit behind the serialization issue:

[System.Xml.Serialization.XmlAttributeAttribute()]

If I comment out all instances of this attribute in the proxy class file and rerun my client app, the SOAP message successfully gets sent across the wire and I get a valid web service response come back from the server.

This fix is better than nothing, but I would very much prefer a solution that doesn't require myself or anyone on my team to constantly tweak these .NET autogenerated proxy class files.

I would like to know if there is something I can do, either through the various WCF tools or by modifying the WSDL file, that prevents that [System.Xml.Serialization.XmlAttributeAttribute()] from being applied to my request and response object properties?

Or at least a high level description of WHY we are seeing this serialization behavior in .NET with the Java WSDL file?

thanks in advance,
John

Best Answer

Use svcutil.exe utility with the /wrapped option on to generate proxy classes.

This will create slightly different classes then those created though Visual Studio in a way described by Ladislav Mrnka here. Resulting proxies should be free from the XmlAttribute issue when using on the client side.

Example:

svcutil /t:code wsdl.xml /out:wsdl.cs /serializer:XmlSerializer /wrapped

Read all text from a file

Java 11 added the readString() method to read small files as a String, preserving line terminators:

String content = Files.readString(path, StandardCharsets.US_ASCII);

For versions between Java 7 and 11, here's a compact, robust idiom, wrapped up in a utility method:

static String readFile(String path, Charset encoding)
  throws IOException
{
  byte[] encoded = Files.readAllBytes(Paths.get(path));
  return new String(encoded, encoding);
}

Read lines of text from a file

Java 7 added a convenience method to read a file as lines of text, represented as a List<String>. This approach is "lossy" because the line separators are stripped from the end of each line.

List<String> lines = Files.readAllLines(Paths.get(path), encoding);

Java 8 added the Files.lines() method to produce a Stream<String>. Again, this method is lossy because line separators are stripped. If an IOException is encountered while reading the file, it is wrapped in an UncheckedIOException, since Stream doesn't accept lambdas that throw checked exceptions.

try (Stream<String> lines = Files.lines(path, encoding)) {
  lines.forEach(System.out::println);
}

This Stream does need a close() call; this is poorly documented on the API, and I suspect many people don't even notice Stream has a close() method. Be sure to use an ARM-block as shown.

If you are working with a source other than a file, you can use the lines() method in BufferedReader instead.

Memory utilization

The first method, that preserves line breaks, can temporarily require memory several times the size of the file, because for a short time the raw file contents (a byte array), and the decoded characters (each of which is 16 bits even if encoded as 8 bits in the file) reside in memory at once. It is safest to apply to files that you know to be small relative to the available memory.

The second method, reading lines, is usually more memory efficient, because the input byte buffer for decoding doesn't need to contain the entire file. However, it's still not suitable for files that are very large relative to available memory.

For reading large files, you need a different design for your program, one that reads a chunk of text from a stream, processes it, and then moves on to the next, reusing the same fixed-sized memory block. Here, "large" depends on the computer specs. Nowadays, this threshold might be many gigabytes of RAM. The third method, using a Stream<String> is one way to do this, if your input "records" happen to be individual lines. (Using the readLine() method of BufferedReader is the procedural equivalent to this approach.)

Character encoding

One thing that is missing from the sample in the original post is the character encoding. There are some special cases where the platform default is what you want, but they are rare, and you should be able justify your choice.

The StandardCharsets class defines some constants for the encodings required of all Java runtimes:

String content = readFile("test.txt", StandardCharsets.UTF_8);

The platform default is available from the Charset class itself:

String content = readFile("test.txt", Charset.defaultCharset());

Note: This answer largely replaces my Java 6 version. The utility of Java 7 safely simplifies the code, and the old answer, which used a mapped byte buffer, prevented the file that was read from being deleted until the mapped buffer was garbage collected. You can view the old version via the "edited" link on this answer.

Wcf – Could not find default endpoint element

"This error can arise if you are calling the service in a class library and calling the class library from another project."

In this case you will need to include the WS configuration settings into the main projects app.config if its a winapp or web.config if its a web app. This is the way to go even with PRISM and WPF/Silverlight.

Best Answer

Related Solutions

Java – How to create a Java string from the contents of a file

Read all text from a file

Read lines of text from a file

Memory utilization

Character encoding

Wcf – Could not find default endpoint element

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