Java some common error exception handling methods summary _java

Some common mistakes and solutions, I am a novice, each encountered errors are recorded.

1.404 Error

Description The requested resource (/struts2_0100_introduction/hello.action) is not available.

Check First . Manager deployments to enable it to open (appear NullPointerException can not be opened, mainly the server before each allow backup, and then modify the error can not be corrected in time. (If the Backup is checked , change to delete)

2. Error Configuring application Listener of Class Org.springframework.web.context.ContextLoaderListener

java.lang.ClassNotFoundException : Org.springframework.web.context.ContextLoaderListener

Port is wrong, port is 3306, I write

For 8080

problem description	problem case	Problem resolution
grave : standardserver.await:create[8005]: [] Java.net.BindException:Address already in Use:jvm_bind	Run independently tomcat.exe not closed installation of other software takes up 8080 Port	close Tomcat icon and end off Tomcat process Tomcat Install the default port is 8080 , scenario One: Change Tomcat Port conf/service.xml , Scenario two: Open cmd command prompt, enter Netstat-ano Find 8080 Port-occupied PID number, and then turn it off in the Task manager details PID The number process.
Error Configuring application Listener of Class Org.springframework.web.context.ContextLoaderListener Java.lang.ClassNotFoundException : Org.springframework.web.context.ContextLoaderListener	Spring3.0 Web librariess package not introduced	rebuild project, add sping Package introduce Spring 3.0 Web Libraries Package
Java.lang.ClassCastException:java.lang.Integer cannot be cast to Java.util.List	Object O=session.getattribute (a); List L = (list) o; cannot be Object object is converted into List	Can't solve, looked for a lot, all said can transform, but I use not. I'm going to put Object object is converted into a String object, and then put it in the List String S=session.geta ... (a). ToString (); List<string> l=new ArrayList (); L.add (s);
Errors occurred during the build. Errors running builder ' Deploymentbuilder ' on Project ' Project Name '. Java.lang.NullPointerException	This problem typically occurs in MyEclipse Save the file and deploy it automatically. Write the project time, not wait for deployment, closed myeclipse, the result of this situation. One reason for this error is that the project is not created by MyEclipse and needs to check the . Project file and add Com.genuitec.eclipse.j2eedt.core.webnature.	1 , first off MyEclipse work space. 2 , and then delete the work space under the /.metadata/.plugins/org.eclipse.core.runtime/.settings/com.genuitec.eclipse.ast.deploy.core.prefs " Cancel MyEclipse the automatic deployment : Right-click item ->properties-> Builders, will be Deploymentbuilder Tick Removal .
Js File Error		Select JS Right Key ->myeclipse->exclude from Validation Tick
Eclipse inside the java EE items are placed in MyEclipse inside running, servlet File Error		Select a servlet where the error is, add a Javaee.jar Wrap it in .
You have a error in your SQL syntax; Check the manual that corresponds to your MySQL server version for the right syntax to use near ' by publishdate Desc 0,8 ' at line 1	There is a problem with the injected database statement	pay particular attention to the " +x+ "The question of whitespace on both sides of the statement
	Clicking the Deploy button is invalid	Find MyEclipse work path to this directory. " \.metadata\.plugins\org.eclipse.core.runtime\.settings "Find a containing Deploy of the . Prefs file deletion can (com.genuitec.eclipse.ast.deploy.core.prefs) . Reboot the myeclipse, and it's OK again .
Type Action Question!list cannot is found in the namespace/		window-->preference-->myeclipse-->validation--> removed struts2 Validator after the Build Column Tick Confirmation ( if not, you can remove all the build columns, no use )

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