struts custom tag-白红宇

struts custom tag

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发布时间：2019-06-29

本文共 3185 字，大约阅读时间需要 10 分钟。

1、<%@ taglib uri="/struts-layout-tags" prefix="layout"%>中struts-layout-tags类


      
     
      yield
         
     
      com.fangdo.core.view.YieldTag
         
     
      JSP
         
     
         
           
      
       id
            
      
       false
            
      
       true
            
      
          
         
           
      
       value
            
      
       false
            
      
       true

2、yieldTag类

继承ComponentTagSupport类是为了获得JSP页面中用户自定义的标签中设置的属性值，并包装成Component对象。

Component:

继承Component类是为了从Struts2中的ValueStack中获得相对应的值。

public class YieldTag extends ComponentTagSupport {	protected String value;		public Component getBean(ValueStack stack, HttpServletRequest req, HttpServletResponse res) {		return new Yield(stack, req, res);	}//protected void populateParams()此方法是用来将JSP页面传来的属性值赋给基本类。这里是继承来的，所以首先调用super的相应方法。 	protected void populateParams() {		super.populateParams();		((Yield) component).setValue(value);	}	public void setValue(String value) {		this.value = value;	}}

3、Yield类

重写start，end等方法即可。

public class Yield extends Component {		private static boolean encodingDefined = true;	private static String encoding;        private static String defaultEncoding;    	private String value;	private HttpServletRequest req;	private HttpServletResponse res;		public Yield(ValueStack stack,HttpServletRequest req,HttpServletResponse res){		super(stack);		this.req = req;		this.res = res;	}    @Inject(StrutsConstants.STRUTS_I18N_ENCODING)    public static void setDefaultEncoding(String encoding) {        defaultEncoding = encoding;    }        private static String getEncoding() {        if (encodingDefined) {            try {                encoding = defaultEncoding;            } catch (IllegalArgumentException e) {                encoding = System.getProperty("file.encoding");                encodingDefined = false;            }        }        return encoding;    }    	@Override	public boolean end(Writer writer, String body) {				String name = StringUtils.isBlank(value) ? "content_for_layout" : "content_for_" + value;		FastByteArrayOutputStream content = (FastByteArrayOutputStream) req.getAttribute(name);		if(content !=null){			String encoding = getEncoding();			try{				if (encoding != null) {				content.writeTo(writer, encoding);	        } else {	        	content.writeTo(writer,null);	        }			} catch(IOException e) {				LogFactory.getLog(getClass()).warn("Exception thrown during ", e);			}		}		return super.end(writer, body);	}	public void setValue(String value) {		this.value = value;	}	}

4、jsp中

<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%><%@ taglib uri="/struts-layout-tags" prefix="layout"%><% String rootPath = request.getContextPath(); %>
    <layout:yield value="title"/>。。。
    
    	
    		
     	
    
	
    		
     	
    
		
    
     south region
    
	
    	
     		
      		
      			
       		
      
	
     
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