listtag.java

来自「weblogic应用全实例」· Java 代码 · 共 64 行

//定义本类所在的包
package examples.jsp.tagext.session;
//定义本类引入的类
import java.io.*;
import java.util.*;
import javax.servlet.http.*;
import javax.servlet.jsp.*;
import javax.servlet.jsp.tagext.*;

/**
 * 这个类定义定制的JSP标签，枚举当前的会话
 */

public class ListTag extends BodyTagSupport {
  static final boolean debug = true;
  Enumeration names;
  HttpSession session;
  
  public int doStartTag() throws javax.servlet.jsp.JspException {
    // 获取JSP页会话
    session = pageContext.getSession();
    
    names = session.getAttributeNames();
    if (names.hasMoreElements())
    {
      // 提取第一个name/value对
      String name = (String)names.nextElement();
      String value = (String)session.getAttribute(name);
      // 设置name和value
      pageContext.setAttribute("name", name);
      pageContext.setAttribute("value", value);
      return BodyTag.EVAL_BODY_TAG;
    } 
    else 
    {
      // 没有名称/值对
      return BodyTag.SKIP_BODY;
    }
  }
  
  public int doAfterBody() throws javax.servlet.jsp.JspException {
    // 获取标签的内容
    if (names.hasMoreElements()) {

      String name = (String)names.nextElement();
      String value = (String)session.getAttribute(name);
      // 
      pageContext.setAttribute("name", name);
      pageContext.setAttribute("value", value);
      
      return EVAL_BODY_TAG;
    }
    else {
      try {
        getBodyContent().writeOut(getPreviousOut());
      } catch (IOException ioe) {
        throw new JspTagException(ioe.toString());
      }
      return SKIP_BODY;
    }
  }
}