"Web Development Learning Note" Struts-tags Learning Note 1-Universal label and Control label

General label and Control label the first part; code

Front 
Struct.xml<constant name= "Struts.ui.theme" value= "simple"/><package name= "tags" extends= "struts-default "><action name=" tags "class=" com.struts2.tags.TagsAction "><result>/tags.jsp</result></ Action></package>
//Class pack Package Com.struts2.tags;import Com.opensymphony.xwork2.actionsupport;public class Tagsaction extends ActionSupport {private String Password;private string Username;public tagsaction () {}public string execute () {This.addfielderror (" Fielderror.test "," wrong! "); return SUCCESS;} Public String GetPassword () {return password;} Public String GetUserName () {return username;} public void SetPassword (String password) {this.password = password;} public void Setusername (String username) {this.username = username;}} 
Show Part II: AnalysisFront End: <a href= "<%=contextpath%>/tags.action?username=u&password=p" >tags</a> after click  , passed on to
Tag.action two parameters of username and password.
 -Struct.xml configuration, invokes the Tagsaction.java class, initializes the object, and sets the initial value on the object. 
<package name= "tags" extends= "struts-default" ><action name= "tags" class= "com.struts2.tags.TagsAction" > <result>/tags.jsp</result></action></package>
based on the result information of the Struct.xml configuration, the results are passed to the tag.jsp shown in the description in the <result>/tags.jsp</result> 
Row value operation;
Part III: General label operations
Property Tags: <li>property: <s:property value= "username"/> </li><li>property value as a string: <s: Property value= "' username '"/> </li><li>property set Default value: <s:property value= "admin" default= "admin"/ > </li><li>property Set HTML: <s:property value= "' 
Analysis:
The property takes a value of string: <s:property value= "' username '"/> when the value in S:proerty in a label is double-quoted with a single quote, the table
The value inside the single quotation mark is treated as a string. 
set label:< Li>set Set AdminName value (default to request and Actioncontext): <s:set var= "AdminName" value= "username"/></li><li >set from Request: <s:property value= "#request. AdminName"/></li><li>set value from Actioncontext: <s: Property value= "#adminName"/></li><s:debug></s:debug><li>set set Var with a range of Actioncontext: <s:set var= "AdminPassword" value= "password" scope= "session"/></li><li>set use # Value: <s:property Value= "#adminPassword"/> </li><li>set value from the corresponding range: <s:property value= "#session. AdminPassword"/> </li> 
Analysis:
The scope value can be set inside the set: scope
Scope  defaults to action and can be achieved with five scopes: the scope in which to assign the variable. Can be application,
session, request, page, or action.
Bean tag: <li>bean defines the bean and uses Param to set the new property value: <s:bean name= "Com.struts2.tags.Dog" ><s:param name= "name" Value= "' pp '" ></s:param><s:property value= "name"/></s:bean></li><li>bean View Debug conditions: <s:bean name= "Com.struts2.tags.Dog" var= "Mydog" ><s:param name= "name" value= "' Oudy '" ></s: Param></s:bean> out value: <s:property value= "#myDog. Name"/></li>
Analysis:
Bean label
The type of the parameter name is string, and the function is the class name of the bean to be instantiated (must respect JavaBean
Specification), define a class that needs to be instantiated.
The method of the value: All start with #, which variable name is the guy
#adminPassword
#session. AdminPassword
#myDog. Name
Notice the two different ways:
<s:bean name= "Com.struts2.tags.Dog" > 
When the S:bean execution begins, an object is constructed to stack to the top of the stack and removed from the top of the stack after execution.
<s:bean name= "Com.struts2.tags.Dog" var= "Mydog" >
Put  in stack Context after execution
Include tag <s:set var= "Incpage" value= "%{'/_include1.html '}"/><s:include value= "%{#incPage}" ></s: Include>
%{} effect: Force it to OGNL expression;
Part IV: Control label operation
set a short name through set;
Part V: Traversing tags
<li> Traversal collection: <br/><s:iterator value= "{1, 2, 3}" ><s:property/> |</s:iterator></li> <li> Custom variables: <br/><s:iterator value= "{' AAA ', ' BBB ', ' CCC '}" var= "x" ><s:property value= "# X.touppercase () "/> |</s:iterator></li>
Analysis: String collection, var = "X" is equivalent to the temporary variable defined in the For loop, each value in the collection is taken out, and the value is placed in X once per loop. Use # to access it. 
<li> using status:<br/><s:iterator value= "{' AAA ', ' BBB ', ' CCC '} ' status= ' status ' ><s:property/> | Total number of traversed elements: <s:property value= "#status. Count"/> | traversed element index: <s:property value= "#status. Index"/> | is currently an even number? : <s:property value= "#status. even"/> | is currently an odd number? : <s:property value= "#status. Odd"/> | is the first element? : <s:property value= "#status. First"/> | Is this the last element? : <s:property value= "#status. Last"/><br/></s:iterator></li>
Analysis: Status action if specified, an instanceof Iteratorstatus'll be pushed to stack upon each iteration
S:property Remove the current value of the loop. To get the loop condition by taking the status value

<li><s:iterator value= "#{1: ' A ', 2: ' B ', 3: ' C '}" ><s:property value= "key"/> | <s:property value= "value"/> <br/></s:iterator></li><li><s:iterator value= "#{1: ' A ', 2: ' B ', 3: ' C '} "var=" x "><s:property value=" #x. Key "/> | <s:property value= "#x. Value"/> <br/></s:iterator></li>
Analysis: When you define a map, you need to precede it with #;