Jsp custom tag

Jsp custom tag

Recently, the project was changed to jsp for all the original static pages. The manager asked me to write a custom jsp tag to handle permission issues, after writing it out, I found that using custom tags to control permissions is much more convenient than the tedious judgment in js on static pages. So I recorded it for later use, the specific method was found in a blog of an unknown friend. Because I searched a lot and was busy with projects and didn't reserve the address, I won't leave the portal here.

First, you need to write a tld file, placed under the WEB-INF, to define the label name, attributes, and background processing class.

 

 
 
  
  
   
A tag library exercising SimpleTag handlers.
  
  
   
1.0
  
  
   
  
   
Crb
  
  
   
/IsHasPermission
  
  
   
JSP Self-define Tag Library.
  
  
   
    
This is an authority tag
   
   
    
   
    
HasPermission
   
   
   
    
Com. zzvc. crb. tag. HasPermission
   
   
   
    
JSP
   
   
   
    
Name
   
   
    
False
   
   
    
True
   
  
 

 

 

 

Where The label attribute is variable. Here, bodycontent has three optional values.
1. jsp: the TAG body is composed of other jsp elements. If there is a jsp element, the tag will be explained first, and the actual value of the element will be passed in. For example, if the TAG body contains jsp elements such as <% = attributeName %>, the tag will be passed in according to the actual value of attributeName. This is the most common one.
2. empty: the Tag body must be empty. When referencing this Tag, you can Instead of having
3. tagdependent: interpreted by tags without jsp Conversion

2. You need to configure the tag in web. xml,

   
    
     
      /crb
     
     
      /WEB-INF/roletag.tld
     
    
   

Iii. Tag Processing

 

 

Public class HasPermission extends TagSupport {private String name; public int doStartTag () throws JspException {HttpSession session = pageContext. getSession (); Person person = (Person) session. getAttribute ("person"); if (person. getAuthorities (). contains (name) {return EVAL_BODY_INCLUDE; // normal execution} else {return SKIP_BODY; // The content is ignored} public int doEndTag () throws JspException {return EVAL_PAGE ;} public String getName () {return name;} public void setName (String name) {this. name = name ;}}

Note:

 

1. This class inherits TagSupport;

2. the attribute of a tag must be written as a member variable and the set and get methods must be claimed.

 

So far, this simple custom tag has been written and can be referenced in jsp:

 

<%@ taglib prefix="crb" uri="/isHasPermission" %>

You can write jsp code in the middle of the tag. If the current user has the permission for the corresponding name value, the jsp code is executed normally. Otherwise, the jsp code is hidden and not visible to the user.

 

This is just a simple custom tag. to implement more complex functions, you only need to enrich the logic processing of the processing class, which is indeed very convenient.