Hello, world. My name is <classe de implementação do tag handler> and it's <data e horas>
<%@ taglib uri="/hello" prefix="examples" %>
<html>
<head>
<title>First custom tag</title>
</head>
<body>
Saida estatica.
<p/>
<i>
<examples:hello>
</examples:hello>
</i>
Mais saida estatica.
</body>
</html>
package tagext;
import java.io.IOException;
import java.util.Date;
import javax.servlet.jsp.*;
import javax.servlet.jsp.tagext.*;
/**
* Implementation of a tag to generate a single piece of HTML.
* @author Rod Johnson
*/
public class HelloTag extends TagSupport {
/**
* This method will be called when the JSP engine encounters the start
* of a tag implemented by this class
*/
public int doStartTag() throws JspTagException {
// This return value means that the JSP engine should evaluate
// the contents and any child tags of this tag
return EVAL_BODY_INCLUDE;
}
/**
* This method will be called when the JSP engine encounters the end
* of a tag implemented by this class
*/
public int doEndTag() throws JspTagException {
String dateString = new Date().toString();
try {
pageContext.getOut().write("Hello world.<br/>");
pageContext.getOut().write("My name is " + getClass().getName() +
" and it's " + dateString + "<p/>");
}
catch (IOException ex) {
throw new JspTagException("Fatal error: hello tag could not write to JSP out");
}
// This return value means that the JSP engine should continue to
// evaluate the rest of this page
return EVAL_PAGE;
}
} // class HelloTag
<?xml version="1.0" encoding="ISO-8859-1" ?>
<!DOCTYPE taglib
PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.1//EN"
"http://java.sun.com/j2ee/dtds/web-jsptaglibrary_1_1.dtd">
<taglib>
<tlibversion>1.0</tlibversion>
<jspversion>1.1</jspversion>
<shortname>examples</shortname>
<info>Simple example library.</info>
<tag>
<name>hello</name>
<tagclass>tagext.HelloTag</tagclass>
<bodycontent>JSP</bodycontent>
<info>Simple example</info>
</tag>
</taglib>
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE web-app PUBLIC '-//Sun Microsystems, Inc.//DTD Web Application 2.2//EN' 'http://java.sun.com/j2ee/dtds/web-app_2.2.dtd'>
<web-app>
<display-name>tagext</display-name>
<description>Tag extensions examples</description>
<session-config>
<session-timeout>0</session-timeout>
</session-config>
<taglib>
<taglib-uri>/hello</taglib-uri>
<taglib-location>/WEB-INF/tlds/hello.tld</taglib-location>
</taglib>
</web-app>
jar -cvf hello.war WEB-INF hello.jsp
O código do handler segue e é fácil de entender quando se sabe que:
package org.apache.struts.webapp.example;
import java.io.IOException;
import javax.servlet.http.HttpSession;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspWriter;
import javax.servlet.jsp.PageContext;
import javax.servlet.jsp.tagext.TagSupport;
import org.apache.struts.action.Action;
import org.apache.struts.util.BeanUtils;
import org.apache.struts.util.MessageResources;
/**
* Check for a valid User logged on in the current session. If there is no
* such user, forward control to the logon page.
*
* @author Craig R. McClanahan
* @author Marius Barduta
* @version $Revision: 1.2 $ $Date: 2001/04/14 12:53:07 $
*/
public final class CheckLogonTag extends TagSupport {
// --------------------------------------------------- Instance Variables
/**
* The key of the session-scope bean we look for.
*/
private String name = Constants.USER_KEY;
/**
* The page to which we should forward for the user to log on.
*/
private String page = "/logon.jsp";
// ----------------------------------------------------------- Properties
/**
* Return the bean name.
*/
public String getName() {
return (this.name);
}
/**
* Set the bean name.
*
* @param name The new bean name
*/
public void setName(String name) {
this.name = name;
}
/**
* Return the forward page.
*/
public String getPage() {
return (this.page);
}
/**
* Set the forward page.
*
* @param page The new forward page
*/
public void setPage(String page) {
this.page = page;
}
// ------------------------------------------------------- Public Methods
/**
* Defer our checking until the end of this tag is encountered.
*
* @exception JspException if a JSP exception has occurred
*/
public int doStartTag() throws JspException {
return (SKIP_BODY);
}
/**
* Perform our logged-in user check by looking for the existence of
* a session scope bean under the specified name. If this bean is not
* present, control is forwarded to the specified logon page.
*
* @exception JspException if a JSP exception has occurred
*/
public int doEndTag() throws JspException {
// Is there a valid user logged on?
boolean valid = false;
HttpSession session = pageContext.getSession();
if ((session != null) && (session.getAttribute(name) != null))
valid = true;
// Forward control based on the results
if (valid)
return (EVAL_PAGE);
else {
try {
pageContext.forward(page);
} catch (Exception e) {
throw new JspException(e.toString());
}
return (SKIP_PAGE);
}
}
/**
* Release any acquired resources.
*/
public void release() {
super.release();
this.name = Constants.USER_KEY;
this.page = "/logon.jsp";
}
}
| present - Generate the nested body content of this tag if the specified value is present in this request. | ||||||||||||||||||
|
||||||||||||||||||
|
package org.apache.struts.taglib.logic;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.TagSupport;
import org.apache.struts.util.MessageResources;
/**
* Abstract base class for the various conditional evaluation tags.
*
* @author Craig R. McClanahan
* @version $Revision: 1.5 $ $Date: 2001/02/12 21:49:54 $
*/
public abstract class ConditionalTagBase extends TagSupport {
// ------------------------------------------------------------- Properties
/**
* The name of the cookie to be used as a variable.
*/
protected String cookie = null;
public String getCookie() {
return (this.cookie);
}
public void setCookie(String cookie) {
this.cookie = cookie;
}
/**
* The name of the HTTP request header to be used as a variable.
*/
protected String header = null;
public String getHeader() {
return (this.header);
}
public void setHeader(String header) {
this.header = header;
}
/**
* The message resources for this package.
*/
protected static MessageResources messages =
MessageResources.getMessageResources
("org.apache.struts.taglib.logic.LocalStrings");
/**
* The name of the JSP bean to be used as a variable (if
* <code>property</code> is not specified), or whose property is to be
* accessed (if <code>property</code> is specified).
*/
protected String name = null;
public String getName() {
return (this.name);
}
public void setName(String name) {
this.name = name;
}
/**
* The name of the HTTP request parameter to be used as a variable.
*/
protected String parameter = null;
public String getParameter() {
return (this.parameter);
}
public void setParameter(String parameter) {
this.parameter = parameter;
}
/**
* The name of the bean property to be used as a variable.
*/
protected String property = null;
public String getProperty() {
return (this.property);
}
public void setProperty(String property) {
this.property = property;
}
/**
* The name of the security role to be checked for.
*/
protected String role = null;
public String getRole() {
return (this.role);
}
public void setRole(String role) {
this.role = role;
}
/**
* The scope to search for the bean named by the name property, or
* "any scope" if null.
*/
protected String scope = null;
public String getScope() {
return (this.scope);
}
public void setScope(String scope) {
this.scope = scope;
}
/**
* The user principal name to be checked for.
*/
protected String user = null;
public String getUser() {
return (this.user);
}
public void setUser(String user) {
this.user = user;
}
// --------------------------------------------------------- Public Methods
/**
* Perform the test required for this particular tag, and either evaluate
* or skip the body of this tag.
*
* @exception JspException if a JSP exception occurs
*/
public int doStartTag() throws JspException {
if (condition())
return (EVAL_BODY_INCLUDE);
else
return (SKIP_BODY);
}
/**
* Evaluate the remainder of the current page normally.
*
* @exception JspException if a JSP exception occurs
*/
public int doEndTag() throws JspException {
return (EVAL_PAGE);
}
/**
* Release all allocated resources.
*/
public void release() {
super.release();
cookie = null;
header = null;
name = null;
parameter = null;
property = null;
role = null;
scope = null;
user = null;
}
// ------------------------------------------------------ Protected Methods
/**
* Evaluate the condition that is being tested by this particular tag,
* and return <code>true</code> if the nested body content of this tag
* should be evaluated, or <code>false</code> if it should be skipped.
* This method must be implemented by concrete subclasses.
*
* @exception JspException if a JSP exception occurs
*/
protected abstract boolean condition() throws JspException;
}
package org.apache.struts.taglib.logic;
import java.security.Principal;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.PageContext;
import org.apache.struts.util.PropertyUtils;
import org.apache.struts.util.RequestUtils;
/**
* Evalute the nested body content of this tag if the specified value
* is present for this request.
*
* @author Craig R. McClanahan
* @version $Revision: 1.7.2.1 $ $Date: 2001/06/11 17:34:40 $
*/
public class PresentTag extends ConditionalTagBase {
// ------------------------------------------------------ Protected Methods
/**
* Evaluate the condition that is being tested by this particular tag,
* and return <code>true</code> if the nested body content of this tag
* should be evaluated, or <code>false</code> if it should be skipped.
* This method must be implemented by concrete subclasses.
*
* @exception JspException if a JSP exception occurs
*/
protected boolean condition() throws JspException {
return (condition(true));
}
/**
* Evaluate the condition that is being tested by this particular tag,
* and return <code>true</code> if the nested body content of this tag
* should be evaluated, or <code>false</code> if it should be skipped.
* This method must be implemented by concrete subclasses.
*
* @param desired Desired outcome for a true result
*
* @exception JspException if a JSP exception occurs
*/
protected boolean condition(boolean desired) throws JspException {
// Evaluate the presence of the specified value
boolean present = false;
if (cookie != null) {
Cookie cookies[] =
((HttpServletRequest) pageContext.getRequest()).
getCookies();
if (cookies == null)
cookies = new Cookie[0];
for (int i = 0; i < cookies.length; i++) {
if (cookie.equals(cookies[i].getName())) {
present = true;
break;
}
}
} else if (header != null) {
String value =
((HttpServletRequest) pageContext.getRequest()).
getHeader(header);
present = (value != null);
} else if (name != null) {
Object value = null;
try {
value =
RequestUtils.lookup(pageContext, name, property, scope);
} catch (JspException e) {
value = null;
}
present = (value != null);
} else if (parameter != null) {
String value =
pageContext.getRequest().getParameter(parameter);
present = (value != null);
} else if (role != null) {
HttpServletRequest request =
(HttpServletRequest) pageContext.getRequest();
present = request.isUserInRole(role);
} else if (user != null) {
HttpServletRequest request =
(HttpServletRequest) pageContext.getRequest();
Principal principal = request.getUserPrincipal();
present = (principal != null) &&
user.equals(principal.getName());
} else {
JspException e = new JspException
(messages.getMessage("logic.selector"));
RequestUtils.saveException(pageContext, e);
throw e;
}
return (present == desired);
}
}
| iterate - Repeat the nested body content of this tag over a specified collection. | ||||||||||||||||||||
|
||||||||||||||||||||
|
package org.apache.struts.taglib.logic;
import java.util.Arrays;
import java.util.Collection;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.Map;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspWriter;
import javax.servlet.jsp.PageContext;
import javax.servlet.jsp.tagext.BodyTagSupport;
import org.apache.struts.util.IteratorAdapter;
import org.apache.struts.util.MessageResources;
import org.apache.struts.util.PropertyUtils;
import org.apache.struts.util.RequestUtils;
import org.apache.struts.util.ResponseUtils;
/**
* Custom tag that iterates the elements of a collection, which can be
* either an attribute or the property of an attribute. The collection
* can be any of the following: an array of objects, an Enumeration,
* an Iterator, a Collection (which includes Lists, Sets and Vectors),
* or a Map (which includes Hashtables) whose elements will be iterated over.
*
* @author Craig R. McClanahan
* @version $Revision: 1.11.2.1 $ $Date: 2001/06/14 04:24:27 $
*/
public class IterateTag extends BodyTagSupport {
// ----------------------------------------------------- Instance Variables
/**
* Iterator of the elements of this collection, while we are actually
* running.
*/
protected Iterator iterator = null;
/**
* The number of elements we have already rendered.
*/
protected int lengthCount = 0;
/**
* The actual length value (calculated in the start tag).
*/
protected int lengthValue = 0;
/**
* The message resources for this package.
*/
protected static MessageResources messages =
MessageResources.getMessageResources
("org.apache.struts.taglib.logic.LocalStrings");
/**
* The actual offset value (calculated in the start tag).
*/
protected int offsetValue = 0;
/**
* Has this tag instance been started?
*/
protected boolean started = false;
// ------------------------------------------------------------- Properties
/**
* The collection over which we will be iterating.
*/
protected Object collection = null;
public Object getCollection() {
return (this.collection);
}
public void setCollection(Object collection) {
this.collection = collection;
}
/**
* The name of the scripting variable to be exposed.
*/
protected String id = null;
public String getId() {
return (this.id);
}
public void setId(String id) {
this.id = id;
}
/**
* <p>Return the zero-relative index of the current iteration through the
* loop. If you specify an <code>offset</code>, the first iteration
* through the loop will have that value; otherwise, the first iteration
* will return zero.</p>
*
* <p>This property is read-only, and gives nested custom tags access to
* this information. Therefore, it is <strong>only</strong> valid in
* between calls to <code>doStartTag()</code> and <code>doEndTag()</code>.
* </p>
*/
public int getIndex() {
if (started)
return (offsetValue + lengthCount - 1);
else
return (0);
}
/**
* The name of the scripting variable to be exposed as the current index.
*/
protected String indexId = null;
public String getIndexId() {
return (this.indexId);
}
public void setIndexId(String indexId) {
this.indexId = indexId;
}
/**
* The length value or attribute name (<=0 means no limit).
*/
protected String length = null;
public String getLength() {
return (this.length);
}
public void setLength(String length) {
this.length = length;
}
/**
* The name of the collection or owning bean.
*/
protected String name = null;
public String getName() {
return (this.name);
}
public void setName(String name) {
this.name = name;
}
/**
* The starting offset (zero relative).
*/
protected String offset = null;
public String getOffset() {
return (this.offset);
}
public void setOffset(String offset) {
this.offset = offset;
}
/**
* The property name containing the collection.
*/
protected String property = null;
public String getProperty() {
return (this.property);
}
public void setProperty(String property) {
this.property = property;
}
/**
* The scope of the bean specified by the name property, if any.
*/
protected String scope = null;
public String getScope() {
return (this.scope);
}
public void setScope(String scope) {
this.scope = scope;
}
/**
* The Java class of each exposed element of the collection.
*/
protected String type = null;
public String getType() {
return (this.type);
}
public void setType(String type) {
this.type = type;
}
// --------------------------------------------------------- Public Methods
/**
* Construct an iterator for the specified collection, and begin
* looping through the body once per element.
*
* @exception JspException if a JSP exception has occurred
*/
public int doStartTag() throws JspException {
// Acquire the collection we are going to iterate over
Object collection = this.collection;
if (collection == null)
collection =
RequestUtils.lookup(pageContext, name, property, scope);
if (collection == null) {
JspException e = new JspException
(messages.getMessage("iterate.collection"));
RequestUtils.saveException(pageContext, e);
throw e;
}
// Construct an iterator for this collection
if (collection.getClass().isArray())
collection = Arrays.asList((Object[]) collection);
if (collection instanceof Collection)
iterator = ((Collection) collection).iterator();
else if (collection instanceof Iterator)
iterator = (Iterator) collection;
else if (collection instanceof Map)
iterator = ((Map) collection).entrySet().iterator();
else if (collection instanceof Enumeration)
iterator = new IteratorAdapter((Enumeration)collection);
else {
JspException e = new JspException
(messages.getMessage("iterate.iterator"));
RequestUtils.saveException(pageContext, e);
throw e;
}
// Calculate the starting offset
if (offset == null)
offsetValue = 0;
else {
try {
offsetValue = Integer.parseInt(offset);
} catch (NumberFormatException e) {
Integer offsetObject =
(Integer) pageContext.findAttribute(offset);
if (offsetObject == null)
offsetValue = 0;
else
offsetValue = offsetObject.intValue();
}
}
if (offsetValue < 0)
offsetValue = 0;
// Calculate the rendering length
if (length == null)
lengthValue = 0;
else {
try {
lengthValue = Integer.parseInt(length);
} catch (NumberFormatException e) {
Integer lengthObject =
(Integer) pageContext.findAttribute(length);
if (lengthObject == null)
lengthValue = 0;
else
lengthValue = lengthObject.intValue();
}
}
if (lengthValue < 0)
lengthValue = 0;
lengthCount = 0;
// Skip the leading elements up to the starting offset
for (int i = 0; i < offsetValue; i++) {
if (iterator.hasNext()) {
Object element = iterator.next();
}
}
// Store the first value and evaluate, or skip the body if none
if (iterator.hasNext()) {
Object element = iterator.next();
if (element == null)
pageContext.removeAttribute(id);
else
pageContext.setAttribute(id, element);
lengthCount++;
started = true;
if (indexId != null)
pageContext.setAttribute(indexId, new Integer(getIndex()));
return (EVAL_BODY_TAG);
} else
return (SKIP_BODY);
}
/**
* Make the next collection element available and loop, or
* finish the iterations if there are no more elements.
*
* @exception JspException if a JSP exception has occurred
*/
public int doAfterBody() throws JspException {
// Render the output from this iteration to the output stream
if (bodyContent != null) {
ResponseUtils.writePrevious(pageContext, bodyContent.getString());
bodyContent.clearBody();
}
// Decide whether to iterate or quit
if ((lengthValue > 0) && (lengthCount >= lengthValue))
return (SKIP_BODY);
if (iterator.hasNext()) {
Object element = iterator.next();
if (element == null)
pageContext.removeAttribute(id);
else
pageContext.setAttribute(id, element);
lengthCount++;
if (indexId != null)
pageContext.setAttribute(indexId, new Integer(getIndex()));
return (EVAL_BODY_TAG);
} else
return (SKIP_BODY);
}
/**
* Clean up after processing this enumeration.
*
* @exception JspException if a JSP exception has occurred
*/
public int doEndTag() throws JspException {
// Clean up our started state
started = false;
// Continue processing this page
return (EVAL_PAGE);
}
/**
* Release all allocated resources.
*/
public void release() {
super.release();
iterator = null;
lengthCount = 0;
lengthValue = 0;
offsetValue = 0;
id = null;
collection = null;
length = null;
name = null;
offset = null;
property = null;
scope = null;
started = false;
}
}
tags programa