J2EE

J2EE - case study (by pew)

---------------------JavaBeans---------------------------
#ProcessListItems.java(servlet)
	ArrayList loanList = (ArrayList) patron.retrieveLoanedCopies();
	if (loanList.size() > 0) {
		LoanedCopyListBean listBean = new LoanedCopyListBean();
		listBean.setLoanedCopyList(loanList);
		session.setAttribute("listitems", listBean);
		context.getRequestDispatcher("/WEB-INF/jsp/ListItems.jsp").forward(req, resp);
	}

#ListItems.jsp
	<jsp:useBean id="listitems" type="com.ibm.library.servlets.LoanedCopyListBean" scope="session"></jsp:useBean>
	<%for (int i = 0; i < listitems.getLoanedCopyList().size(); i++) {
		pageContext.setAttribute("item", listitems.getLoanedCopyList(i));%>
		<jsp:useBean id="item" class="com.ibm.library.model.LoanedCopy"	scope="page"></jsp:useBean>
		<TD align="center"><jsp:getProperty name="item" property="author" /></TD>
		<TD align="center"><jsp:getProperty name="item" property="title" /></TD>
	<%}%>

---------------------Using JSP Expressioon Language (EL)-----------
#ListItems.jsp
	<jsp:useBean id="listitems"
	type="com.ibm.library.servlets.LoanedCopyListBean" scope="session"></jsp:useBean>
		<%for (int i = 0; i < listitems.getLoanedCopyList().size(); i++) {
			pageContext.setAttribute("item", listitems.getLoanedCopyList(i));%>
			<TD align="center">${item.author}</TD>
			<TD align="center">${item.title}</TD>
		<%}%>

--------------------------JSP Custom Taggs--------------------------
#ListItems.jsp
<%@taglib uri="/WEB-INF/tld/taglib.tld" prefix="ilib"%>
		<c:forEach items="${listitems.loanedCopyList}" var="item">
				<TD><INPUT type="checkbox" name="RENEW_ITEM" value="${item.itemId}"></TD>
				<TD align="center"><ilib:hilite name="item" color="red">${item.author}</ilib:hilite></TD>
				<TD align="center"><ilib:hilite name="item" color="red">${item.title}</ilib:hilite></TD>
		</c:forEach>
#/WEB-INF/tld/taglib.tld
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE taglib PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.2//EN" "web-jsptaglibrary_1_2.dtd" >
<taglib>
  <tlib-version>1.2</tlib-version>
  <jsp-version>2.0</jsp-version>
  <short-name>ilib</short-name>
  <tag>
    <name>hilite</name>
    <tag-class>com.ibm.library.tags.MarkRenewedTag</tag-class>
    <attribute>
    	<name>name</name>
    	<required>true</required>
    </attribute>
    <attribute>
    	<name>color</name>
    	<required>false</required>
    </attribute>
  </tag>
</taglib>
#com.ibm.library.tags.MarkRenewedTag

package com.ibm.library.tags;

import ...;

public class MarkRenewedTag extends SimpleTagSupport {
	private String color = "green";
	private String name;
	public MarkRenewedTag() {	super();}
	public void setColor(String color) {this.color = color;}
	public void setName(String name) {	this.name = name;}
	public void doTag() throws JspException, IOException {
		Object obj = getJspContext().findAttribute(name);
		if (obj == null) {
			throw new JspException("Hilite tag: Name " + name + " not found");
		}
		// Is this an object of type com.ibm.library.LoanedCopy?
		if (!obj.getClass().equals(com.ibm.library.model.LoanedCopy.class)) {
			throw new JspException("Hilite tag: Name is not of type "
					+ "com.ibm.library.model.LoanedCopy");
		}
		// Set flag if the item was in fact renewed
		boolean renewed = ((LoanedCopy) obj).isRenewAccomplished();

// Process tag body	
		StringWriter bodyText = new StringWriter();
		JspFragment body = getJspBody();
		if (body != null) {
			body.invoke(bodyText);
			StringBuffer buffer = new StringBuffer();
			// Place font and bold tags at start of body 
			// if renewed flag set
			if (renewed) {
				buffer.append("<b><font color=\"");
				buffer.append(color);
				buffer.append("\">");
			}
			// Copy in the body for either case
			buffer.append(bodyText.toString());	
			// Place font end tag at end of body if renewed
			if (renewed) {
				buffer.append("</font></b>");
			}
			try {
				JspWriter out = getJspContext().getOut();
				out.write(buffer.toString());
			} catch (IOException e) {
				throw new JspException("Hilite tag: " + e.getMessage());
			}
		}
	}
}
(JavaServer Pages Standard Tag Library(JSTL):<forEach>)