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| |
| <document> |
| |
| <properties> |
| <title>BCEL FAQ</title> |
| </properties> |
| |
| <body> |
| |
| <section name="FAQ"> |
| <p> |
| <b>Q: </b>How can I ... with BCEL? |
| <br/> |
| <b>A: </b>Take a look at |
| <tt>org.apache.bcel.util.BCELifier</tt>, it takes a given class |
| and converts it to a BCEL program (in Java, of course). It will |
| show you how certain code is generated using BCEL. |
| </p> |
| |
| <p> |
| <b>Q: </b> Is the BCEL thread-safe? |
| <br/> |
| <b>A: </b>BCEL was (deliberately) not designed for thread |
| safety. See <a href="http://java.sun.com/docs/books/cp/"> |
| "Concurrent Programming in Java"</a>, by Doug Lea, |
| for an excellent reference on how to build thread-safe wrappers. |
| </p> |
| |
| <p> |
| <b>Q: </b> Can I use BCEL in a commercial product? |
| <br/> |
| <b>A: </b> Yes, this is covered by the <a |
| href="http://www.apache.org/licenses/">Apache License</a>, if you add a note about the original |
| author and where to find the sources, i.e., |
| <a href="http://commons.apache.org/bcel/">http://commons.apache.org/bcel/</a> |
| </p> |
| |
| <p> |
| <b>Q: </b> (Typically for users of Xalan (XSLTC)) I'm getting |
| <pre> |
| ClassGenException: Branch target offset too large for short |
| </pre> |
| when compiling large files. |
| <br/> |
| |
| <b>A: </b> The answer lies in internal limitations of the JVM, |
| branch instruction like goto can not address offsets larger than |
| a short integer, i.e. offsets >= 32767.<br/> |
| The solution is to split the branch into in intermediate hops, |
| which the XSLTC obviously doesn't take care off. |
| (In fact you could replace gotos with the goto_w instruction, |
| but this wouldn't help in the other cases). |
| </p> |
| |
| <p> |
| <b>Q:</b> Can I create or modify classes dynamically with BCEL? |
| <br/> |
| <b>A:</b> BCEL contains useful classes in the |
| <tt>util</tt> package, namely <tt>ClassLoader</tt> and |
| <tt>JavaWrapper</tt>. Take a look at the <tt> ProxyCreator</tt> example. |
| </p> |
| |
| <p> |
| <b>Q:</b> I get a verification error, what can I do? |
| <br/> |
| <b>A:</b> Use the JustIce verifier that comes together with BCEL |
| to get more detailed information: |
| <pre> |
| java org.apache.bcel.verifier.Verifier <your class></pre> |
| </p> |
| |
| </section> |
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| </document> |
