Common Servlet Debugging methods

In "Servlet and JSP core programming" see this paragraph, feel very useful, excerpt down, for later use

(1) Use of print statements, such as frequent occurrence of nullpointerexception

(2) Dubug function of integrated development environment

(3) using log files

(4) Use Apache log4j

(5) writing a separate class; putting frequently used code into a separate class or method

(6) Prepare for missing or abnormal data in advance

(7) Check HTML source code

(8) Separate check request data

(9) Separate check response data

(10) Stop and restart the server