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Java web project get HTTP Status 500 – Internal Server Error and The import com.sun.java.swing.plaf.windows.resources cannot be resolved

I can not run my java web project. I got HTTP Status 500 – Internal Server Error from the web and The import com.sun.java.swing.plaf.windows.resources cannot be resolved from the eclipse
After I downloaded a web project from GitHub and made some configurations, the project can run successfully. But as soon as I try to connect the web to MySQL, that is the function of login. The web went wrong. And I got this
Type Exception Report
Description The server encountered an unexpected condition that prevented it from fulfilling the request.
Exception
java.lang.NullPointerException
com.ascent.dao.LoginDAO.login(LoginDAO.java:40)
com.ascent.servlet.LoginServlet.userLogin(LoginServlet.java:183)
com.ascent.servlet.LoginServlet.doGet(LoginServlet.java:39)
com.ascent.servlet.LoginServlet.doPost(LoginServlet.java:31)
javax.servlet.http.HttpServlet.service(HttpServlet.java:682)
javax.servlet.http.HttpServlet.service(HttpServlet.java:765)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
com.ascent.util.ChangeCharsetFilter.doFilter(ChangeCharsetFilter.java:22)
Note The full stack trace of the root cause is available in the server logs.
And the eclipse has an error`The import com.sun.java.swing.plaf.windows.resources cannot be resolved`and plenty of warnings such as 'pst' is not closed at this location LoginDAO.java`.
The code of the project seems correct because my friends can log in successfully.

'pst' is not closed at this location LoginDAO.java means that you have resources which is not closed, such as a database connection etc. You should close it after use, the code below:
Connection con = DriverManager.getConnection(url:"url", user:"root", password:"password");
con.close();
It is more common to maintain a connection pool of database, such as hikariCP
The import com.sun.java.swing.plaf.windows.resources cannot be resolved I think your code import duplicate package, you can check your code again. Hope the answer helps you!

GlassFish HTTP Status 500 - Internal Server Error(JSTL)

When I try to run my Web Application using JSP, the GlassFish server returns the follow message:
HTTP Status 500 - Internal Server Error
type Exception report
messageInternal Server Error
descriptionThe server encountered an internal error that prevented it from fulfilling this request.
exception
javax.servlet.ServletException: javax.servlet.jsp.JspException: Unable to get connection, DataSource invalid: "java.sql.SQLException: Error in allocating a connection. Cause: Class name is wrong or classpath is not set for : com.mysql.jdbc.jdbc2.optional.MysqlDataSource"
root cause
javax.servlet.jsp.JspException: Unable to get connection, DataSource invalid: "java.sql.SQLException: Error in allocating a connection. Cause: Class name is wrong or classpath is not set for : com.mysql.jdbc.jdbc2.optional.MysqlDataSource"
note The full stack traces of the exception and its root causes are available in the GlassFish Server Open Source Edition 5.1.0 logs.
GlassFish Server Open Source Edition 5.1.0
And I don't knhow what to do. I think the error is connected to Can't find javax.servlet.jsp.jstl.jar library in glassfish server

You will need to make the MySQL JDBC jar file available to Glassfish.
https://dev.mysql.com/doc/connector-j/5.1/en/connector-j-usagenotes-glassfish-config.html

So I have figured it out, all I had to do was to set the datasource class name to
com.mysql.cj.jdbc.MysqlDataSource
since I was using MySql connetor J version 8.
Initally I had set the datasource class name to
com.mysql.jdbc.jdbc2.optional.MySqlDataSource

spring-saml IDPSSODescriptor wasn't found after time

I have a system that works, but after certain period of time I have this kind of problem:
2017-08-31 15:31:00 ERROR UT005023: Exception handling request to /spring-security-saml2-sample/saml/login: javax.servlet.ServletException: org.opensaml.saml2.metadata.provider.MetadataProviderException: Metadata for entity ****** and role {urn:oasis:names:tc:SAML:2.0:metadata}IDPSSODescriptor wasn't found
2017-08-31 15:31:02,922 ERROR [io.undertow.request] (default task-29) UT005023: Exception handling request to /spring-security-saml2-sample/: org.apache.jasper.JasperException: java.lang.NullPointerException
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:473)
My "express" solution is to restart wildfly but I'd like to resolve it definitively. What can I do?

I recently ran into this same issue using CachingMetadataManager. In the docs, it says,
Cache is cleaned whenever some of the providers published an observed
message
My current guess is that the IDP either published a message and one of our severs didn't get it, or that the IDP made changes to the metadata without publishing a message. However, simply rebuilding the environment did fix the issue.

How to enable server stack-trace for Rest calls in IBM Mobile First 8

In MF8, when I try to hit Rest Service URLs I am unable to get the stack trace when server returns a 500 error. I get the below error in POSTMAN.
"Unexpected error in server, see logs"
How can I enable the server stack trace?

It's unclear if you're using the devkit or the Mobile Foundation service.
Assuming you're using the devkit, you can find the logs in the devkit-folder/mfp-server/usr/servers/mfp/logs folder... there you will see a messages.log file.

Apache Roller Weblogger Configuration for ORACLE

I am using Apache Roller 5.0.1 Weblogger, deploying in Tomcat6.0.29 with Oracle database with all the configration in roller-custom.properties.
I am able to login and create a blog. but after creating a blog if i try to access the created blog by the link **//localhost:8080/roller/blogname** in the browser but i am getting an Unexpected Exception:
Status Code: 500
Message
Type
Exception: Roller has encountered and logged an unexpected exception
Can anyone help?