1. Frequent 500 error
Caused by the java.long.NopointException.
The main reason is not login.jsp landing page, resulting in session and no content. Nature can not get to in the follow-up.
2.Failed to load resource: the server responded with a status of 404 (Not Found)
Error from servlet path.
At this time whether @WebServlet ( "/ xxxxServlet") form before Notes 1. Check servlet
2. Check the xml <servlet> and <servlet-mapping> tag path, whether the corresponding content.
3.javax.mail.MessagingException: Could not connect（xxxxxx）, port: 25
Display server refused access.
- to SMTP host: smtp.exmail.qq.com QQ server refused access, possibly because too many meaningless to send e-mail server is QQ pull the black.
- HMeailServer own domain name on the server itself is not open
4.java.io.FileNotFoundException: C: \ Program Files (x86) \ hMailServer \ Data \ record \ pp \ {xxxxxxxxxx} .emal (system can not find the path specified.)
5.Invalid Character
In the case of the code is correct, the biggest possibility is that because the code tail ";" there is a problem.
6.The type java.lang.String cannot be resolved. It is indirectly referenced from required .class files
The main reason is because multiple versions of jdk installed on your computer. The program jkd and inconsistent use of the installation caused.
Solution: project-> properties-> Java Bulid Path-> Libraries, select the original jdk, remove.
Libraries-> Add Libraries-> JRE System Library, choose your own installation of jdk-> apply and close
7.java.sql.SQLException: Field 'id' doesn't have a default value
Solution: The error of the ID field is set to auto-incremented.
