org.rhq.enterprise.gui.legacy.taglib
Class ConstantsTag

java.lang.Object
  javax.servlet.jsp.tagext.TagSupport
      org.rhq.enterprise.gui.legacy.taglib.ConstantsTag

All Implemented Interfaces:

Serializable, javax.servlet.jsp.tagext.IterationTag, javax.servlet.jsp.tagext.JspTag, javax.servlet.jsp.tagext.Tag

Direct Known Subclasses:

ConstantsDiagTag

public class ConstantsTag
extends javax.servlet.jsp.tagext.TagSupport

A sensible way to handle constants in a webapp is to define a bean that holds all of the constants as attributes. However, Java programmers have a propensity for creating constants as classes that have the values defined static final members. This tag exposes these attribute handles to save the developer from having to read the constants class source code to determine the returned values. This way the JSP source and the backend bean (and/or bean handlers) have a consistent interface to the constants class.

Under the hood, the tag uses reflection to build a map of names and values. The map is cached to save the expense of repeated runtime reflection.

Usage: Suppose you have a class com.example.Constants:

public class Constants { public static final int WARMRESTART = 0; public static final int COLDRESTART = 1; public static final int HARDRESTART = 2; public static final String RO = "rock"; public static final String SHAM = "paper"; public static final String BO = "scissors"; }

and you want to uniformly access the symbold names in the jsp as you would in your Java classes. Use this tag.

<%@ taglib uri="/WEB-INF/constants.tld" prefix="constants" %> ... someplace where a constant needs to be accessed: Important: This usage assumes the class to access is specified in a web-xml/context-param

The alternate form can be used to accomadate having multiple constants classes.

Another usage is set attributes, within an optionally specified scope or just to put it in the page scope. Either way, at sometime later, you can do this

Author:

Hyperic, Ian Springer (added support for Enums)

See Also:

Serialized Form

Field Summary

protected static Map	constants
static String	constantsClassNameParam

Fields inherited from class javax.servlet.jsp.tagext.TagSupport

id, pageContext

Fields inherited from interface javax.servlet.jsp.tagext.IterationTag

EVAL_BODY_AGAIN

Fields inherited from interface javax.servlet.jsp.tagext.Tag

EVAL_BODY_INCLUDE, EVAL_PAGE, SKIP_BODY, SKIP_PAGE

Constructor Summary

ConstantsTag()

Method Summary

protected void	die(javax.servlet.jsp.JspWriter out)
protected void	die(javax.servlet.jsp.JspWriter out, String err)
int	doEndTag()
protected void	doOutput(Map fieldMap, javax.servlet.jsp.JspWriter out)
protected void	doSet(Map fieldMap)
String	getClassname()
boolean	getFailmode()
String	getScope()
String	getSymbol()
String	getVar()
void	release()
void	setClassname(String aClass)
void	setFailmode(boolean theFailmode)
void	setScope(String aScopeName)
void	setSymbol(String aSymbol)
void	setVar(String aVar)
protected boolean	validate(javax.servlet.jsp.JspWriter out) Checks for broken configuration/attribute combinations.

Methods inherited from class javax.servlet.jsp.tagext.TagSupport

doAfterBody, doStartTag, findAncestorWithClass, getId, getParent, getValue, getValues, removeValue, setId, setPageContext, setParent, setValue

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

constants

protected static Map constants

constantsClassNameParam

public static final String constantsClassNameParam

See Also:

Constant Field Values

Constructor Detail

ConstantsTag

public ConstantsTag()

Method Detail

setClassname

public void setClassname(String aClass)

getClassname

public String getClassname()

setVar

public void setVar(String aVar)

getVar

public String getVar()

setFailmode

public void setFailmode(boolean theFailmode)

getFailmode

public boolean getFailmode()

setSymbol

public void setSymbol(String aSymbol)

getSymbol

public String getSymbol()

setScope

public void setScope(String aScopeName)

getScope

public String getScope()

release

public void release()

Specified by:

release in interface javax.servlet.jsp.tagext.Tag

Overrides:

release in class javax.servlet.jsp.tagext.TagSupport

doEndTag

public int doEndTag()
             throws javax.servlet.jsp.JspException

Specified by:

doEndTag in interface javax.servlet.jsp.tagext.Tag

Overrides:

doEndTag in class javax.servlet.jsp.tagext.TagSupport

Throws:

javax.servlet.jsp.JspException

doOutput

protected void doOutput(Map fieldMap,
                        javax.servlet.jsp.JspWriter out)
                 throws IOException

Throws:

IOException

doSet

protected void doSet(Map fieldMap)

validate

protected boolean validate(javax.servlet.jsp.JspWriter out)
                    throws javax.servlet.jsp.JspException

Checks for broken configuration/attribute combinations.

Returns:

true is validation fails

Throws:

javax.servlet.jsp.JspException

die

protected void die(javax.servlet.jsp.JspWriter out)
            throws javax.servlet.jsp.JspException

Throws:

javax.servlet.jsp.JspException

die

protected void die(javax.servlet.jsp.JspWriter out,
                   String err)
            throws javax.servlet.jsp.JspException

Throws:

javax.servlet.jsp.JspException