Reprint-STRUTS2 Interceptor Configuration

Source: http://blog.csdn.net/axin66ok/article/details/7321430

Directory (?) [-]

1. Understanding Interceptors
1. 1 What is an interceptor?
2. 2 How to implement the Interceptor
2. Interceptor Configuration
3. Using interceptors
4. Custom Interceptors
1. 1 Implementing the Interceptor class
2. 2 Using custom Interceptors
5. Custom Interceptor Sample
1. 1 Problem description
2. 2 Implementing the Rights control interceptor class
3. 3 Configuring the Rights control Interceptor
4. 4 Run debugging

1. Understanding Interceptor 1.1. What is an interceptor:

Interceptors, which are used in AOP (aspect-oriented programming) to intercept a method or field before it is accessed, and then add some action before or after it. Interception is an implementation strategy of AOP.

The Chinese document in WebWork is interpreted as--interceptors are objects that dynamically intercept action calls. It provides a mechanism to enable developers to define code that executes before and after an action executes, or to prevent it from executing before an action executes. It also provides a way to extract the reusable parts of an action.

When it comes to interceptors, there's one more word you should know-the interceptor chain (Interceptor Chain, called the Interceptor stack interceptor stack in struts 2). The Interceptor chain is a chain that binds the interceptor in a certain order. When accessing an intercepted method or field, interceptors in the interceptor chain are called in the order in which they were previously defined.

1.2. How to implement the Interceptor:

Most of the time, the Interceptor method is invoked in the form of proxies. The block implementation of Struts 2 is relatively straightforward. When the request arrives at the servletdispatcher of Struts 2, struts 2 looks for the configuration file, instantiates the relative interceptor object based on its configuration, and then strings it into a list, the last one to invoke the interceptor in the list. Such as:

2. Interceptor Configuration

Struts 2 has provided you with a wide range of fully functional interceptor implementations. You can view the configuration of the default interceptor and Interceptor chain in the struts-default.xml of the Struts2 jar package.

STRUTS2 (Xwork) provides an interceptor function description:

Interception device	Name	Description
Alias Interceptor	Alias	The request parameter is converted between different requests and the request content is unchanged.
Chaining Interceptor	Chain	The property of the previous action can be accessed by the latter action, and is now used in conjunction with the chain type of result (<result type= "Chain" >).
Checkbox Interceptor	CheckBox	Added a checkbox to automatically process the code, setting the contents of the unchecked checkbox to False, while HTML does not submit a checkbox that is not checked by default.
Cookies Interceptor	Cookies	Use the configured Name,value to refer to cookies
Conversion Error Interceptor	Conversionerror	Add the error from Actioncontext to the action's property field.
Create Session Interceptor	CreateSession	The httpsession is automatically created to serve interceptors that need to use the httpsession.
Debugging Interceptor	Debugging	Provide different debugging pages to show the internal data condition.
Execute and Wait Interceptor	Execandwait	Executes the action in the background and takes the user to an intermediate waiting page.
Exception Interceptor	exception	Position the exception to a screen
File Upload Interceptor	FileUpload	Provide file Upload function
I18N Interceptor	i18n	Record User-selected locale
Logger Interceptor	Logger	The name of the output action
Message Store Interceptor	Store	Stores or accesses the message, Error, field error, and so on of the action class that implements the Validationaware interface.
Model Driven Interceptor	Model-driven	If a class implements Modeldriven, the results of Getmodel are placed in the value stack.
Scoped Model Driven	Scoped-model-driven	If an action implements Scopedmodeldriven, the interceptor will remove the model from the corresponding scope by invoking the Setmodel method of the action to put it inside the action.
Parameters Interceptor	Params	Set the parameters in the request to the action.
Prepare Interceptor	Prepare	If Acton implements Preparable, the interceptor invokes the prepare method of the action class.
Scope Interceptor	Scope	A simple way to put the action state into session and application.
Servlet Config Interceptor	ServletConfig	Provides access to HttpServletRequest and HttpServletResponse methods, which are accessed in map mode.
Static Parameters Interceptor	Staticparams	From the Struts.xml file, set the contents of <param> in <action> to the corresponding action.
Roles Interceptor	Roles	Determines whether the user has a role specified by Jaas, otherwise it is not executed.
Timer Interceptor	Timer	Output the time the action was executed
Token Interceptor	Token	Use tokens to avoid double-clicking
Token Session Interceptor	Tokensession	Same as token interceptor, but when you double-click to store the requested data in session
Validation Interceptor	Validation	Verifies the submitted data using the content defined in the Action-validation.xml file.
Workflow Interceptor	Workflow	Call the action's Validate method, and once the error returns, relocate to the input screen
Parameter Filter Interceptor	N/A	Remove unnecessary parameters from the parameter list
Profiling Interceptor	Profiling	Activate profile by parameter

To define the interceptor in the Struts.xml file, the Interceptor stack:

<package name= "My" extends= "Struts-default" namespace= "/manage" > <interceptors> <!--defining Interceptors-- <interceptor name= "Interceptor name" class= "Interceptor implementation Class"/> <!--defining Interceptor stacks-- <interceptor-stack name= "Interceptor stack name" > <interceptor-ref name= "Interceptor One"/> <interceptor-ref name= "Interceptor Two"/> </interceptor-stack> </interceptors> ...... </package>

3. Using interceptors

Once you have defined the interceptor and interceptor stack, you can use this interceptor or interceptor stack to intercept the action. The Interceptor's interception behavior will be executed before the action's Exceute method executes.

<action name= "useropt" class= "Org.qiujy.web.struts2.action.UserAction" > <result name= "Success" >/success.jsp</result> <result name= "Error" >/error.jsp</result> <!--use interceptors, typically configured after result-- <!--referencing the system's default interceptor-- <interceptor-ref name= "Defaultstack"/> <interceptor-ref name= "Interceptor name or Interceptor stack name"/> </action>

It is important to note that if an interceptor is specified for the action, the default interceptor stack of the system will be out of effect. To continue using the default interceptor, the default interceptor is manually introduced in the configuration file above.

4. Custom Interceptors

As a framework, extensibility is essential. While Struts 2 provides us with such a rich interceptor implementation, this does not mean that we lose the ability to create custom interceptors, and on the contrary, it is quite easy to customize interceptors in Struts 2.

4.1. Implement the Interceptor class:

All Struts 2 interceptors implement interface Com.opensymphony.xwork2.interceptor.Interceptor directly or indirectly. The interface provides three methods:

1) void Init (); After the interceptor is initialized, the system backs up the method before the interceptor performs interception. For each interceptor, this method executes only once.

2) void Destroy (); The method corresponds to the init () method. The system will callback this method until the interceptor instance is destroyed.

3) String intercept (actioninvocation invocation) throws Exception; This method is the interception action that the user needs to implement. The method returns a string as a logical view.

In addition, inheriting class com.opensymphony.xwork2.interceptor.AbstractInterceptor is a simpler way to implement an interceptor class, because this class provides an empty implementation of the Init () and Destroy () methods. This way we only need to implement the Intercept method.

4.2. Use a custom interceptor:

Two steps:

L define interceptors by <interceptor ...> elements.

L use interceptors by <interceptor-ref ...> elements.

5. Custom Interceptor Example 5.1. Problem Description:

Use a custom interceptor to complete control of user permissions: When a viewer needs to request an action, the app needs to check if the browser is logged in and has sufficient permissions to perform the operation.

5.2. Implement the Rights control interceptor class:

Authorizationinterceptor.java

Package Org.qiujy.common; import Java.util.Map; import com.opensymphony.xwork2.Action; import com.opensymphony.xwork2.ActionInvocation; import com.opensymphony.xwork2.interceptor.AbstractInterceptor; /** * Permission Check Blocker * * @author qiujy * @version 1.0 */ Public class Authorizationinterceptor extends abstractinterceptor { /* * Interception method to intercept action handling * */ Public String Intercept (actioninvocation invocation) throws Exception { Map session = Invocation.getinvocationcontext (). GetSession (); String userName = (string) session.get ("UserName"); if (null ! = userName && username.equals ("test")) { System. out. println ("Interceptor: Legitimate User Login---"); return Invocation.invoke (); } Else { System. out. println ("Interceptor: User not logged in---"); return Action. LOGIN; } } }

5.3. Configure the rights control interceptor:

Struts.xml:

<! DOCTYPE Struts Public "-//apache software foundation//dtd Struts Configuration 2.0//en" "Http://struts.apache.org/dtds/struts-2.0.dtd" > <struts> <package name= "My" extends= "Struts-default" > <interceptors> <!--define rights control interceptors-- <interceptor name= "authority" class= "Org.qiujy.common.AuthorizationInterceptor"/> </interceptors> <!--define global processing results- <global-results> <!--The result of logic named login, mapped to/login.jsp page-- <result name= "Login" >/login.jsp</result> </global-results> <action name= "Listall" class= "org.qiujy.web.struts2.action.UserAction" method= "Listalluser" > <result name= "Success" >/listall.jsp</result> <!--using Interceptors-- <interceptor-ref name= "Defaultstack"/> <interceptor-ref name= "authority"/> </action> <action name= "useropt" class= "Org.qiujy.web.struts2.action.UserAction" > <result name= "Success" >/success.jsp</result> </action> </package> </struts>

See the source code for other pages.

5.4. Run the debug:

In the browser address bar directly enter Http://localhost:8080/AuthorityInterceptorDemo/listall.action to access, this action is configured with a rights blocker, all are transferred to the login page.

After logging in:

Re-visit http://localhost:8080/AuthorityInterceptorDemo/listall.action this link:

If you want to simplify the configuration of the Struts.xml file and avoid repeatedly configuring the interceptor on each action, you can configure the interceptor as a default interceptor stack. As follows:

<! DOCTYPE Struts Public "-//apache software foundation//dtd Struts Configuration 2.0//en" "Http://struts.apache.org/dtds/struts-2.0.dtd" > <struts> <package name= "My" extends= "Struts-default" > <interceptors> <!--define rights control interceptors-- <interceptor name= "authority" class= "Org.qiujy.common.AuthorizationInterceptor"/> <!--define an interceptor stack with permission controls-- <interceptor-stack name= "Mydefault" > <interceptor-ref name= "Defaultstack"/> <interceptor-ref name= "authority"/> </interceptor-stack> </interceptors> <!--define the default interceptor-- <default-interceptor-ref name= "Mydefault"/> <!--define global processing results- <global-results> <!--The result of logic named login, mapped to/login.jsp page-- <result name= "Login" >/login.jsp</result> </global-results> <action name= "Listall" Class= "Org.qiujy.web.struts2.action.UserAction" method= "Listalluser" > <result name= "Success" >/listall.jsp</result> </action> </package> <package name= "Font" extends= "Struts-default" > <action name= "useropt" class= "Org.qiujy.web.struts2.action.UserAction" > <result name= "Success" >/success.jsp</result> </action> </package> </struts>

Once the default interceptor stack is defined under a package, all actions under that package will use this interceptor stack. For those that do not want to use the interceptor stack, you should place it under a different package.

Reprint-STRUTS2 Interceptor Configuration