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This article mainly analyzes the relevant knowledge points of the common mistakes in Struts, the content is detailed and easy to understand, the operation details are reasonable, and has a certain reference value. If you are interested, you might as well follow the editor to have a look, and follow the editor to learn more about the common mistakes in Struts.

A comprehensive summary of common errors in Struts

1. "No bean found under attribute key XXX"

An ActionForm is defined in struts-config.xml, but the class specified by the type attribute does not exist, and the value of the type attribute should be the full name of the Form class. Or, in the definition of Action, the ActionForm specified by the name or attribute attribute does not exist.

2. "Cannot find bean XXX in any scope"

It is common to request.setAttribute () some objects in Action, and then get them in the transferred jsp file (using the tag or request.getAttribute () method) and display them. This exception means that jsp wants to get an object, but the previous Action does not set the object to request (which can also be session, servletContext).

Maybe the name is wrong, please check the general name property of tag in jsp, or the parameter value of the getAttribute () method, or if there is something wrong with the Action logic, you turn first without executing the setAttribute () method.

There is another possibility that it is purely a problem with the jsp file, such as specifying an id value and then using that value as the name value in the loop, and this exception will occur if the two values are different. (it's all the same. There is no corresponding object in request.)

3. "Missing message for key" XXX "

If you lack the required resources, check if there are any resources needed in the jsp file in the ApplicationResources.properties file, for example:

This line of code looks for the msg.name.prompt resource, and this exception will occur if it is not in the AppliationResources.properties. When using multiple modules, be careful to specify the name of the resource file to be used in the module's struts-config-xxx.xml, otherwise, of course, no resources can be found, which is also an easy mistake.

4. "No getter method for property XXX of bean teacher"

This exception message is a common error in Struts. A bean attribute should be taken from jsp, but this bean does not have this attribute. You should check the value of the property attribute of a tag in jsp. For example, the cade in the following code should be changed to code:

5. "Cannot find ActionMappings or ActionFormBeans collection"

To be solved.

6. "Cannot retrieve mapping for action XXX"

In the .jsp

Action='/XXX', is specified in the tag, but this Action is not set in struts-config.xml.

7. HTTP Status 404-/ xxx/xxx.jsp

The jsp page pointed to by the path attribute of Forward does not exist, please check the path and module, for Action redirection in the same module, the path should not contain the module name; redirect between modules, remember to use contextRelative= "true".

8. Without any abnormal information, a blank page is displayed.

It may be that the forward used in Action does not match the forward name defined in struts-config.xml.

9. "The element type" XXX "must be terminated by the matching end-tag" XXX. "

This is an error in the format of the struts-config.xml file. Check carefully whether it is a well-formed xml file. I will not repeat the format of the xml file here.

10. "Servlet.init () for servlet action threw exception"

Typically, this exception is followed by an exception stack message about ActionServlet, indicating exactly which line of code the exception occurs in. One of the tips I once encountered was as follows:

Java.lang.NullPointerException

At org.apache.struts.action.ActionServlet.parseModuleConfigFile (ActionServlet.java:1003)

At org.apache.struts.action.ActionServlet.initModuleConfig (ActionServlet.java:955)

To solve the problem, download the source package for struts, then insert a breakpoint on line 1003 of ActionServlet.java, and monitor the variables. It's a shame that I lost the struts-config.xml file, so the above exception occurred, which should have been accidentally deleted when synchronizing with CVS.

11. "Resources not defined for Validator"

This is the exception that may occur when using the Validator plug-in for verification. In the common errors in Struts, you should check the validation.xml file to see if the resources used in it are really defined, whether the name of form is correct, and so on.

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