Shulou(Shulou.com)06/03 Report--

Title: in-depth understanding of the operating mechanism of struts

Date: 2016-10-26 20:02

Tags: java

Categories: programming

Permalink: zxh

Personal analysis, do not spray if you like it.

Scan the code to follow the official account and update the work irregularly.

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I would like to declare that this blog post is not original, the original article: http://blog.csdn.net/lenotang/article/details/3336623, this article is optimized on the basis of this article. It's not optimization, it's just a little bit of my own idea.

Jar package preparation

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Why do I use these two jar packages, because I need this jar to parse the xml configuration file.

New project

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Process carding

Struts profile

/ index.jsp

/ WEB-INF/login.jsp

Friends who are familiar with struts are aware of the importance of the struts.xml configuration file. The name of this configuration file can be changed. Here we briefly explain the function of this configuration file. First of all, we find that the name of the action node, this action, is login. That is to say, after the foreground requests the login to parse the configuration file, it will give the request to the class attribute in the action, that is, the above.

Org.zxh.action.LoginAction

Specifically, it is passed to the login (method) method of this class. This method methods a string of type string, and redirects the page to index.jsp if success is returned. If it is login, redirect to login.jsp. That's what this configuration file does. Because I wrote it myself, I don't encapsulate a lot of things like the struts framework, but just to give readers a deeper understanding of how struts works.

How to start the struts.xml file we wrote in the program?

Beginner comrades may wonder, write a configuration file can deal with the front and background interaction? The answer is, of course, no. Here to popularize the web basic contact with filter, each interaction requires filter (jsp is a special servlet), so if we want to achieve interaction, we have to create a new servlet, in which we read the struts.xml file we wrote, and determine the next step through the information we read. So how do you start a filter? Needless to say, configuring the interceptor directly in the web.xml in the web project will execute filter.

Create a new filter (FilterDispatcher)

This servlet is the core filter of struts, which needs to be inherited first.

`

Public class FilterDispatcher implements Filter {

@ Override

Public void destroy () {

/ / TODO Auto-generated method stub

}

@ Override

Public void doFilter (ServletRequest arg0, ServletResponse arg1

FilterChain arg2) throws IOException, ServletException {

/ / TODO Auto-generated method stub

}

@ Override

Public void init (FilterConfig arg0) throws ServletException {

/ / TODO Auto-generated method stub

}

}

`

In Filter, we need to initialize some parameters in the initialization function (init). Initialize those data. Yes! Take the configuration file information, of course. The configuration file is .xml. Here I use dom4j to read the .xml configuration file. Put the struts.xml configuration file under src (you can put it somewhere else, just fill in the corresponding address here)

/ / obtain the xml configuration file

String webRootPath = getClass () .getClassLoader ()

.getResource ("struts.xml") .getPath ()

After getting the configuration file path, we start to read. Here, the data I read is encapsulated in a map. Let's take a closer look at the configuration file after encapsulating it in Map

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In fact, we put the values of these four attributes in Map, with these four values, we can complete a mapping of the front and background interaction. So in order to facilitate the packaging here into javabean.

Package org.zxh.util

Import java.util.HashMap

Import java.util.Map

/ * *

* encapsulate the action attribute into a class

* @ author 87077

*

, /

Public class ActionConfig {

/ / the name that action calls to others

Private String name

/ / action class in action corresponding program

Private String clazzName

/ / methods in action

Private String method

/ / the returned result is unknown, so use Map

Private Map resultMap = new HashMap ()

Public ActionConfig () {

}

Public ActionConfig (String name, String clazzName, String method, Map resultMap) {

This.name=name

This.clazzName=clazzName

This.method=method

This.resultMap=resultMap

}

Public String getName () {

Return name

}

Public String getClazzName () {

Return clazzName

}

Public String getMethod () {

Return method

}

Public Map getResultMap () {

Return resultMap

}

Public void setName (String name) {

This.name = name

}

Public void setClazzName (String clazzName) {

This.clazzName = clazzName

}

Public void setMethod (String method) {

This.method = method

}

Public void setResultMap (Map resultMap) {

This.resultMap = resultMap

}

}

With javabean, we start parsing the xml file.

Package org.zxh.util

Import java.io.File

Import java.util.List

Import java.util.Map

Import org.dom4j.Document

Import org.dom4j.DocumentException

Import org.dom4j.Element

Import org.dom4j.io.SAXReader

/ * *

* parsing xml configuration files using dom4j

*

* @ author 87077

*

, /

Public class ConfigUtil {

/ * *

* @ param fileName

* Files to be parsed

* @ param map

* storing parsed data

, /

Public static void parseConfigFile (String fileName

Map map) {

SAXReader reader = new SAXReader ()

Try {

Document doc = reader.read (new File ("D:\\ zxh\\ soft\\ apache-tomcat-7.0.70\\ apache-tomcat-7.0.70\\ webapps\\ MyStruts\\ WEB-INF\\ classes\\ struts.xml"))

Element root = doc.getRootElement ()

List list = root.selectNodes ("package/action")

For (Element element: list) {

/ / encapsulated into an ActionConfig object and saved in map

ActionConfig config = new ActionConfig ()

/ / get the value in action

String name = element.attributeValue ("name")

String clazzName = element.attributeValue ("class")

String method = element.attributeValue ("method")

/ / pass the value into javabean

Config.setName (name)

Config.setClazzName (clazzName)

/ / if the execution method is not set to execute the default

If (method = = null | | ".equals (method)) {

Method = "execute"

}

Config.setMethod (method)

/ / continue to get the return method in action.

List resultList = element.selectNodes ("result")

For (Element resultElement: resultList) {

String resultName = resultElement.attributeValue ("name")

String urlPath = resultElement.getTextTrim ()

If (resultName = = null | | ".equals (resultName)) {

ResultName = "success"

}

Config.getResultMap () .put (resultName urlPath)

}

Map.put (name, config)

}

} catch (DocumentException e) {

/ / TODO Auto-generated catch block

E.printStackTrace ()

}

}

}

Now let's go back to the filter, and the above two classes are used to parse xml. So in the init method in Filter, we can put the parsed data into our global Map.

@ Override

Public void init (FilterConfig arg0) throws ServletException {

/ / initialization process of TODO Auto-generated method stub filter

/ / obtain the xml configuration file

String webRootPath = getClass () .getClassLoader ()

.getResource ("struts.xml") .getPath ()

/ / parsing the xml configuration file into map

ConfigUtil.parseConfigFile (webRootPath, map)

}

Implementation of filter

The filter is actually executed at the beginning of the doFilter method.

Public void doFilter (ServletRequest arg0, ServletResponse arg1

FilterChain arg2)

The doFilter () method is similar to the service () method of the Servlet interface. When the client requests the target resource, the container invokes the doFilter () method of the filter associated with the target resource. Parameters request and response are the requests and corresponding objects passed by the last Filter of the web container or Filter chain The parameter chain represents the object of the current Filter chain. After a specific operation is completed, you can call the chain.doFilter (request,response) method of the FilterChain object to deliver the request to the next Filter or target Servlet program in the Filter chain for processing, or you can return the response information directly to the client, or use the forward () and include () methods of RequestDispatcher, and the sendRedirect () method of HttpServletResponse to direct the request to other resources. The request and response parameters of this method are of the types ServletRequest and ServletResponse, that is, the use of the filter does not depend on the specific protocol.

Get the request domain and response domain as well as the Filter chain, and set the code to prevent garbled

/ / for http requests, restore the request and response types to HTTP types

HttpServletRequest request = (HttpServletRequest) arg0

HttpServletResponse response = (HttpServletResponse) arg1

/ / set the coding problem of request and response

Request.setCharacterEncoding ("UTF-8")

Response.setCharacterEncoding ("UTF-8")

Get the request address

/ / get the request path

String url = request.getServletPath ()

By request to determine whether to intercept and filter requests for this address, this article filters all requests ending in .action by default.

/ / request address filtering, if it does not end in .action

If (! url.endsWith (".action")) {

/ / not the release of .action

Arg2.doFilter (request, response)

Return

}

Looking at the format in which I put the data in the xml file into Map, you can see that I am talking about putting the whole javabean into the name named action in Map. So next I'm going to that name (that is, the login in the request)

/ / resolve the request path

Int start = url.indexOf ("/")

Int end = url.lastIndexOf (. ")

String path=url.substring (start+1,end)

/ / match to the corresponding ActionConfig class through path. All the action information has been parsed here.

ActionConfig config = map.get (path)

/ / if the match is not successful, the error message of the page cannot be found

If (config==null) {

Response.setStatus (response.SC_NOT_FOUND)

Return

}

Now that you have the ActionConfig class, and all the information about action is stored in this javabean class, the following things are easy to do. The following is just the knowledge that will be used in reflection. After we get the name of the real action class, we need to get the entity class of the action by name.

/ / obtain the completed class name through ActionConfig

String clazzName=config.getClazzName ()

/ / instantiate the Action object and prompt an error message if it does not exist

Object action = getAction (clazzName)

If (action==null) {

/ / indicates that the action is incorrect and does not occupy the corresponding action class in the configuration file.

Response.setStatus (response.SC_NOT_FOUND)

Return

}

The request parameter is obtained and assigned to action

Before executing the method of action, it is necessary to get the parameters in request and assign them. This is the real interaction.

Public static void requestToAction (HttpServletRequest request, Object action)

Class the incoming action object and get the attributes under the action entity

Class

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