Javassist CannotCompileException when trying to add a line to create a Map

问题

um trying to instrument a method to do the following task. Task - Create a Map and insert values to the map Adding System.out.println lines wouldn't cause any exception. But when i add the line to create the Map, it throws a cannotCompileException due to a missing ;. When i print the final string it doesn't seem to miss any. What am i doing wrong here.

public void createInsertAt(CtMethod method, int lineNo, Map<String,String> parameterMap)
            throws CannotCompileException {
        StringBuilder atBuilder = new StringBuilder();
        atBuilder.append("System.out.println(\"" + method.getName() + " is running\");");
        atBuilder.append("java.util.Map<String,String> arbitraryMap = new java.util.HashMap<String,String>();");

        for (Map.Entry<String,String> entry : parameterMap.entrySet()) {
        }
        System.out.println(atBuilder.toString());
        method.insertAt(1, atBuilder.toString());
    }

String obtained by printing the output of string builder is,

System.out.println("prepareStatement is running");java.util.Map arbitraryMap = new java.util.HashMap();

Exception received is,

javassist.CannotCompileException: [source error] ; is missing
    at javassist.CtBehavior.insertAt(CtBehavior.java:1207)
    at javassist.CtBehavior.insertAt(CtBehavior.java:1134)
    at org.wso2.das.javaagent.instrumentation.InstrumentationClassTransformer.createInsertAt(InstrumentationClassTransformer.java:126)
    at org.wso2.das.javaagent.instrumentation.InstrumentationClassTransformer.instrumentMethod(InstrumentationClassTransformer.java:100)
    at org.wso2.das.javaagent.instrumentation.InstrumentationClassTransformer.transform(InstrumentationClassTransformer.java:37)
    at sun.instrument.TransformerManager.transform(TransformerManager.java:188)
    at sun.instrument.InstrumentationImpl.transform(InstrumentationImpl.java:424)
    at sun.instrument.InstrumentationImpl.retransformClasses0(Native Method)
    at sun.instrument.InstrumentationImpl.retransformClasses(InstrumentationImpl.java:144)
    at org.wso2.das.javaagent.instrumentation.Agent.premain(Agent.java:39)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:606)
    at sun.instrument.InstrumentationImpl.loadClassAndStartAgent(InstrumentationImpl.java:382)
    at sun.instrument.InstrumentationImpl.loadClassAndCallPremain(InstrumentationImpl.java:397)
Caused by: compile error: ; is missing
    at javassist.compiler.Parser.parseDeclarationOrExpression(Parser.java:594)
    at javassist.compiler.Parser.parseStatement(Parser.java:277)
    at javassist.compiler.Javac.compileStmnt(Javac.java:567)
    at javassist.CtBehavior.insertAt(CtBehavior.java:1186)
    ... 15 more

(Is there any way to debug these kind of issues.) Some help please.....

回答1:

Javassist's compiler doesn't support generics. Either remove or comment them out:

.append("java.util.Map arbitraryMap = new java.util.HashMap();")

.append("java.util.Map/*<String,String>*/ arbitraryMap = new java.util.HashMap/*<String,String>*/();")

The latter is useful as comment for yourself only, of course, it has no special meaning for Javassist.

来源：https://stackoverflow.com/questions/33279914/javassist-cannotcompileexception-when-trying-to-add-a-line-to-create-a-map

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