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How to override a class file from a library JAR in a Java web app

 

The answer depends upon your container, it is container dependent. In general, /WEB-INF/classes is preferred to classes in a jar file in WEB-INF/lib.

For Tomcat, the order is the following:

Therefore, from the perspective of a web application, class or resource loading looks in the following repositories, in this order:

1. Bootstrap classes of your JVM
2. System class loader classes
3. /WEB-INF/classes of your web application
4. /WEB-INF/lib/*.jar of your web application
5. Common class loader classes

But if you're using a different container, you need to consult the documentation for that server.

结论是： /WEB-INF/classes比/WEB-INF/lib/*.jar有更高的优先级，系统会优先寻找classes folder内的文件，然后再寻找jar，因此在web application创建一个同名文件，编译后将被优先读取。。。

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