1. Set the js file editor code
2. Set the project deployment location, whether it is the Tomcat installation directory or the workspace location
3. Set the output location of the class file after the Java source file is compiled
4. The Java class files are not recompiled after modification.
If it still does not work, delete the JRE library from the build library and add it again.
http://www.jb51.net/article/76306.htm