Causes of getting a java.lang.VerifyError

I'm investigating the following java.lang.VerifyError

java.lang.VerifyError: (class: be/post/ehr/wfm/application/serviceorganization/report/DisplayReportServlet, method: getMonthData signature: (IILjava/util/Collection;Ljava/util/Collection;Ljava/util/HashMap;Ljava/util/Collection;Ljava/util/Locale;Lorg/apache/struts/util/MessageRe˜̴Mt̴MÚw€mçw€mp:”MŒŒ
                at java.lang.Class.getDeclaredConstructors0(Native Method)
                at java.lang.Class.privateGetDeclaredConstructors(Class.java:2357)
                at java.lang.Class.getConstructor0(Class.java:2671)

It occurs when the jboss server in which the servlet is deployed is started. It is compiled with jdk-1.5.0_11 and I tried to recompile it with jdk-1.5.0_15 without succes. That is the compilation runs fine but when deployed, the java.lang.VerifyError occurs.

When I changed the method name and got the following error:

java.lang.VerifyError: (class: be/post/ehr/wfm/application/serviceorganization/report/DisplayReportServlet, method: getMD signature: (IILjava/util/Collection;Lj    ava/util/Collection;Ljava/util/HashMap;Ljava/util/Collection;Ljava/util/Locale;Lorg/apache/struts/util/MessageResources ØÅN|ØÅNÚw€mçw€mX#ÖM|XÔM
            at java.lang.Class.getDeclaredConstructors0(Native Method)
            at java.lang.Class.privateGetDeclaredConstructors(Class.java:2357
            at java.lang.Class.getConstructor0(Class.java:2671)
            at java.lang.Class.newInstance0(Class.java:321)
            at java.lang.Class.newInstance(Class.java:303)

You can see that more of the method signature is shown.

The actual method signature is

  private PgasePdfTable getMonthData(int month, int year, Collection dayTypes,
                          Collection calendarDays,
                          HashMap bcSpecialDays,
                          Collection activityPeriods,
                          Locale locale, MessageResources resources) throws   Exception {

I already tried looking at it with javap and that gives the method signature as it should be.

When my other colleagues check out the code, compile it and deploy it, they have the same problem. When the build server picks up the code and deploys it on development or testing environments (HPUX), the same error occurs. Also an automated testing machine running Ubuntu shows the same error during server startup.

The rest of the application runs okay, only that one servlet is out of order. Any ideas where to look would be helpful.

java.lang.VerifyError can be the result when you have compiled against a different library than you are using at runtime.

For example, this happened to me when trying to run a program that was compiled against Xerces 1, but Xerces 2 was found on the classpath. The required classes (in org.apache.* namespace) were found at runtime, so ClassNotFoundException was not the result. There had been changes to the classes and methods, so that the method signatures found at runtime did not match what was there at compile-time.

Normally, the compiler will flag problems where method signatures do not match. The JVM will verify the bytecode again when the class is loaded, and throws VerifyError when the bytecode is trying to do something that should not be allowed -- e.g. calling a method that returns String and then stores that return value in a field that holds a List.

java.lang.VerifyError are the worst.

You would get this error if the bytecode size of your method exceeds the 64kb limit; but you would probably have noticed that.

Are you 100% sure this class isn't present in the classpath elsewhere in your application, maybe in another jar?

Also, from your stacktrace, is the character encoding of the source file (utf-8?) Is that correct?

As Kevin Panko said, it's mostly because of library change. So in some cases a "clean" of the project (directory) followed by a build does the trick.