import java.util.Collection;
import java.util.Iterator;

import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.BodyContent;
import javax.servlet.jsp.tagext.BodyTagSupport;

public class ForEach  extends BodyTagSupport
{
  private String id;
  private String collection;
  private Iterator iter;
  
  public void setCollection(String collection)
  {
    this.collection = collection;
  }
  public void setId(String id)
  {
    this.id = id;
  }
  
  //遇到开始标签执行
  public int doStartTag() throws JspException
  {
    Collection coll = (Collection) pageContext.findAttribute(collection);
    // 表示如果未找到指定集合，则不用处理标签体，直接调用doEndTag()方法。
    if(coll==null||coll.isEmpty()) return SKIP_BODY;
    
    iter = coll.iterator();
    pageContext.setAttribute(id, iter.next());
    // 表示在现有的输出流对象中处理标签体，但绕过setBodyContent()和doInitBody()方法
    // 这里一定要返回EVAL_BODY_INCLUDE，否则标签体的内容不会在网页上输出显示
    return EVAL_BODY_INCLUDE;
  }
  
  //在doInitBody方法之前执行，在这里被绕过不执行
  @Override
  public void setBodyContent(BodyContent arg0)
  {
    System.out.println("setBodyContent...");
    super.setBodyContent(arg0);
  }
  //此方法被绕过不会被执行
  @Override
  public void doInitBody() throws JspException
  {
    System.out.println("doInitBody...");
    super.doInitBody();
  }
  
  //遇到标签体执行
  public int doAfterBody() throws JspException
  {
    if(iter.hasNext()) 
    {
      pageContext.setAttribute(id, iter.next());
      return EVAL_BODY_AGAIN;// 如果集合中还有对像，则循环执行标签体
    }
    return SKIP_BODY;//迭代完集合后，跳过标签体，调用doEndTag()方法。
  }
  
  //遇到结束标签执行
  public int doEndTag() throws JspException
  {
    System.out.println("doEndTag...");
    return EVAL_PAGE;
  }

}

import java.lang.reflect.Method;

import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.BodyTagSupport;

public class GetProperty extends BodyTagSupport
{

  private String name;
  private String property;

  public void setName(String name)
  {
    this.name = name;
  }

  public void setProperty(String property)
  {
    this.property = property;
  }

  @SuppressWarnings("unchecked")
  public int doStartTag() throws JspException
  {
    try
    {
      Object obj = pageContext.findAttribute(name);
      
      if (obj == null) return SKIP_BODY;
      
      Class c = obj.getClass();
      //构造GET方法名字 get+属性名(属性名第一个字母大写)
      String getMethodName = "get" + property.substring(0, 1).toUpperCase() 
                              + property.substring(1, property.length());
      Method getMethod = c.getMethod(getMethodName, new Class[]{});
      
      pageContext.getOut().print(getMethod.invoke(obj));
      System.out.print(property + ":" + getMethod.invoke(obj) + "\t");
    } catch (Exception e)
    {
      e.printStackTrace();
    }
    return SKIP_BODY;
  }

  public int doEndTag() throws JspException
  {
    return EVAL_PAGE;
  }
}