Common JSP + Servlet Errors for beginners, jspservlet for beginners

Common JSP + Servlet Errors for beginners, jspservlet for beginners

Common Errors in web programming:

I. 404 (the resource to be accessed is not found)

1. Whether the web program is deployed (add the project to tomcat)

2. Are there any url errors (including case sensitivity, including whether the project has been renamed)

3. Have you put jsp/html in the WEB-INF?

4. If you access servlet, check whether the configuration in url-pattern in web. xml is consistent with the name you wrote.

 

Ii. 500 (the program has an exception, that is, the Code has a problem)

1. ClassNotFoundException

Tip: oracle. jdbc. driver. OracleDriver

1. Check whether the jar package of oracle is in the project.
2. Check whether the driver class package name. class name has an error.

 

2. SQLException (..........)

JDBC operation, URL, username, and password Problems

 

 

3. java.net. BindException: Address already in use: JVM_Bind: 8080

Cause: port 8080 is already in use, that is, there are at least two servers in use.

1. In the task manager, check that there are two javaw.exe(atat5.exe). Disable the following one.

 

4. java. lang. NumberFormatException: null

An error occurred while formatting the number.

Cause: null

Receives a null value and forcibly converts the value to a number.

Solution: Pass the value at the request