javax.servlet.jsp.el.ImplicitObjectELResolver Maven / Gradle / Ivy
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package javax.servlet.jsp.el;
import java.beans.FeatureDescriptor;
import java.util.Iterator;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;
import javax.servlet.ServletContext;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.jsp.PageContext;
import javax.servlet.jsp.JspContext;
import javax.el.PropertyNotWritableException;
import javax.el.ELContext;
import javax.el.ELResolver;
/**
* Defines variable resolution behavior for the EL implicit objects
* defined in the JSP specification.
*
* The following variables are resolved by this ELResolver,
* as per the JSP specification:
*
* pageContext - the PageContext object.pageScope - a Map that maps page-scoped
* attribute names to their values.requestScope - a Map that maps
* request-scoped attribute names to their values.sessionScope - a Map that maps
* session-scoped attribute names to their values.applicationScope - a Map that maps
* application-scoped attribute names to their values.param - a Map that maps parameter
* names to a single String parameter value (obtained by calling
* ServletRequest.getParameter(String name)).paramValues - a Map that maps parameter
* names to a String[] of all values for that
* parameter (obtained by calling
* ServletRequest.getParameterValues(String name)).header - a Map that maps header names
* to a single String header value (obtained by calling
* HttpServletRequest.getHeader(String name)).headerValues - a Map that maps header
* names to a String[] of all values for that header
* (obtained by calling
* HttpServletRequest.getHeaders(String)).cookie - a Map that maps cookie names
* to a single Cookie object. Cookies are retrieved
* according to the semantics of
* HttpServletRequest.getCookies(). If the same name
* is shared by multiple cookies, an implementation must use the
* first one encountered in the array of Cookie objects
* returned by the getCookies() method. However, users
* of the cookie implicit object must be aware that the ordering
* of cookies is currently unspecified in the servlet
* specification.initParam - a Map that maps context
* initialization parameter names to their String parameter
* value (obtained by calling
* ServletContext.getInitParameter(String name)).
*
* @see javax.el.ELResolver
* @since JSP 2.1
*/
public class ImplicitObjectELResolver extends ELResolver {
/**
* If the base object is null, and the property matches
* the name of a JSP implicit object, returns the implicit object.
*
* The propertyResolved property of the
* ELContext object must be set to true by
* this resolver before returning if an implicit object is matched. If
* this property is not true after this method is called,
* the caller should ignore the return value.
*
* @param context The context of this evaluation.
* @param base Only null is handled by this resolver.
* Other values will result in an immediate return.
* @param property The name of the implicit object to resolve.
* @return If the propertyResolved property of
* ELContext was set to true, then
* the implicit object; otherwise undefined.
* @throws NullPointerException if context is null
* @throws ELException if an exception was thrown while performing
* the property or variable resolution. The thrown exception
* must be included as the cause property of this exception, if
* available.
*/
public Object getValue(ELContext context,
Object base,
Object property) {
if (context == null) {
throw new NullPointerException();
}
if (base != null) {
return null;
}
PageContext ctxt = (PageContext)context.getContext(JspContext.class);
if ("pageContext".equals(property)) {
context.setPropertyResolved(true);
return ctxt;
}
ImplicitObjects implicitObjects =
ImplicitObjects.getImplicitObjects(ctxt);
if ("pageScope".equals(property)) {
context.setPropertyResolved(true);
return implicitObjects.getPageScopeMap();
}
if ("requestScope".equals(property)) {
context.setPropertyResolved(true);
return implicitObjects.getRequestScopeMap();
}
if ("sessionScope".equals(property)) {
context.setPropertyResolved(true);
return implicitObjects.getSessionScopeMap();
}
if ("applicationScope".equals (property)) {
context.setPropertyResolved(true);
return implicitObjects.getApplicationScopeMap ();
}
if ("param".equals (property)) {
context.setPropertyResolved(true);
return implicitObjects.getParamMap();
}
if ("paramValues".equals (property)) {
context.setPropertyResolved(true);
return implicitObjects.getParamsMap();
}
if ("header".equals (property)) {
context.setPropertyResolved(true);
return implicitObjects.getHeaderMap();
}
if ("headerValues".equals (property)) {
context.setPropertyResolved(true);
return implicitObjects.getHeadersMap();
}
if ("initParam".equals (property)) {
context.setPropertyResolved(true);
return implicitObjects.getInitParamMap ();
}
if ("cookie".equals (property)) {
context.setPropertyResolved(true);
return implicitObjects.getCookieMap ();
}
return null;
}
/**
* If the base object is null, and the property matches
* the name of a JSP implicit object, returns null to
* indicate that no types are ever accepted to setValue().
*
* The propertyResolved property of the
* ELContext object must be set to true by
* this resolver before returning if an implicit object is matched. If
* this property is not true after this method is called,
* the caller should ignore the return value.
*
* @param context The context of this evaluation.
* @param base Only null is handled by this resolver.
* Other values will result in an immediate return.
* @param property The name of the implicit object to resolve.
* @return If the propertyResolved property of
* ELContext was set to true, then
* null; otherwise undefined.
* @throws NullPointerException if context is null
* @throws ELException if an exception was thrown while performing
* the property or variable resolution. The thrown exception
* must be included as the cause property of this exception, if
* available.
*/
public Class getType(ELContext context,
Object base,
Object property) {
if (context == null) {
throw new NullPointerException();
}
if ((base == null) && ("pageContext".equals(property) ||
"pageScope".equals(property)) ||
"requestScope".equals(property) ||
"sessionScope".equals(property) ||
"applicationScope".equals (property) ||
"param".equals (property) ||
"paramValues".equals (property) ||
"header".equals (property) ||
"headerValues".equals (property) ||
"initParam".equals (property) ||
"cookie".equals (property)) {
context.setPropertyResolved(true);
}
return null;
}
/**
* If the base object is null, and the property matches
* the name of a JSP implicit object, throws
* PropertyNotWritableException to indicate that implicit
* objects cannot be overwritten.
*
* The propertyResolved property of the
* ELContext object must be set to true by
* this resolver before returning if an implicit object is matched. If
* this property is not true after this method is called,
* the caller should ignore the return value.
*
* @param context The context of this evaluation.
* @param base Only null is handled by this resolver.
* Other values will result in an immediate return.
* @param property The name of the implicit object.
* @param val The value to be associated with the implicit object.
* @throws NullPointerException if context is null.
* @throws PropertyNotWritableException always thrown, if the
* implicit object name is recognized by this resolver.
* @throws ELException if an exception was thrown while performing
* the property or variable resolution. The thrown exception
* must be included as the cause property of this exception, if
* available.
*/
public void setValue(ELContext context,
Object base,
Object property,
Object val) {
if (context == null) {
throw new NullPointerException();
}
if ((base == null) && ("pageContext".equals(property) ||
"pageScope".equals(property)) ||
"requestScope".equals(property) ||
"sessionScope".equals(property) ||
"applicationScope".equals (property) ||
"param".equals (property) ||
"paramValues".equals (property) ||
"header".equals (property) ||
"headerValues".equals (property) ||
"initParam".equals (property) ||
"cookie".equals (property)) {
throw new PropertyNotWritableException();
}
}
/**
* If the base object is null, and the property matches
* the name of a JSP implicit object, returns true
* to indicate that implicit objects cannot be overwritten.
*
* The propertyResolved property of the
* ELContext object must be set to true by
* this resolver before returning if an implicit object is matched. If
* this property is not true after this method is called,
* the caller should ignore the return value.
*
* @param context The context of this evaluation.
* @param base Only null is handled by this resolver.
* Other values will result in an immediate return.
* @param property The name of the implicit object.
* @return If the propertyResolved property of
* ELContext was set to true, then
* true; otherwise undefined.
* @throws NullPointerException if context is null.
* @throws ELException if an exception was thrown while performing
* the property or variable resolution. The thrown exception
* must be included as the cause property of this exception, if
* available.
*/
public boolean isReadOnly(ELContext context,
Object base,
Object property) {
if (context == null) {
throw new NullPointerException();
}
if ((base == null) && ("pageContext".equals(property) ||
"pageScope".equals(property)) ||
"requestScope".equals(property) ||
"sessionScope".equals(property) ||
"applicationScope".equals (property) ||
"param".equals (property) ||
"paramValues".equals (property) ||
"header".equals (property) ||
"headerValues".equals (property) ||
"initParam".equals (property) ||
"cookie".equals (property)) {
context.setPropertyResolved(true);
return true;
}
return false; // Doesn't matter
}
/**
* If the base object is null, and the property matches
* the name of a JSP implicit object, returns an Iterator
* containing FeatureDescriptor objects with information
* about each JSP implicit object resolved by this resolver. Otherwise,
* returns null.
*
* The Iterator returned must contain one instance of
* {@link java.beans.FeatureDescriptor} for each of the EL implicit objects
* defined by the JSP spec. Each info object contains information about
* a single implicit object, and is initialized as follows:
*
*
displayName - The name of the implicit object.
* name - Same as displayName property.
* shortDescription - A suitable description for the implicit
* object. Will vary by implementation.
* expert - false
* hidden - false
* preferred - true
*
* In addition, the following named attributes must be set in the
* returned FeatureDescriptors:
*
*
{@link ELResolver#TYPE} - The runtime type of the implicit object.
* {@link ELResolver#RESOLVABLE_AT_DESIGN_TIME} - true.
*
*
* @param context The context of this evaluation.
* @param base Only null is handled by this resolver.
* Other values will result in a null return value.
* @return An Iterator containing one
* FeatureDescriptor object for each implicit object, or
* null if base is not null.
*/
public Iterator getFeatureDescriptors(
ELContext context,
Object base) {
ArrayList list =
new ArrayList(11);
// pageContext
FeatureDescriptor descriptor = new FeatureDescriptor();
descriptor.setName("pageContext");
descriptor.setDisplayName("pageContext");
//descriptor.setShortDescription("");
descriptor.setExpert(false);
descriptor.setHidden(false);
descriptor.setPreferred(true);
descriptor.setValue("type", javax.servlet.jsp.PageContext.class);
descriptor.setValue("resolvableAtDesignTime", Boolean.TRUE);
list.add(descriptor);
// pageScope
descriptor = new FeatureDescriptor();
descriptor.setName("pageScope");
descriptor.setDisplayName("pageScope");
//descriptor.setShortDescription("");
descriptor.setExpert(false);
descriptor.setHidden(false);
descriptor.setPreferred(true);
descriptor.setValue("type", Map.class);
descriptor.setValue("resolvableAtDesignTime", Boolean.TRUE);
list.add(descriptor);
// requestScope
descriptor = new FeatureDescriptor();
descriptor.setName("requestScope");
descriptor.setDisplayName("requestScope");
//descriptor.setShortDescription("");
descriptor.setExpert(false);
descriptor.setHidden(false);
descriptor.setPreferred(true);
descriptor.setValue("type", Map.class);
descriptor.setValue("resolvableAtDesignTime", Boolean.TRUE);
list.add(descriptor);
// sessionScope
descriptor = new FeatureDescriptor();
descriptor.setName("sessionScope");
descriptor.setDisplayName("sessionScope");
//descriptor.setShortDescription("");
descriptor.setExpert(false);
descriptor.setHidden(false);
descriptor.setPreferred(true);
descriptor.setValue("type", Map.class);
descriptor.setValue("resolvableAtDesignTime", Boolean.TRUE);
list.add(descriptor);
// applicationScope
descriptor = new FeatureDescriptor();
descriptor.setName("applicationScope");
descriptor.setDisplayName("applicationScope");
//descriptor.setShortDescription("");
descriptor.setExpert(false);
descriptor.setHidden(false);
descriptor.setPreferred(true);
descriptor.setValue("type", Map.class);
descriptor.setValue("resolvableAtDesignTime", Boolean.TRUE);
list.add(descriptor);
// param
descriptor = new FeatureDescriptor();
descriptor.setName("param");
descriptor.setDisplayName("param");
//descriptor.setShortDescription("");
descriptor.setExpert(false);
descriptor.setHidden(false);
descriptor.setPreferred(true);
descriptor.setValue("type", Map.class);
descriptor.setValue("resolvableAtDesignTime", Boolean.TRUE);
list.add(descriptor);
// paramValues
descriptor = new FeatureDescriptor();
descriptor.setName("paramValues");
descriptor.setDisplayName("paramValues");
//descriptor.setShortDescription("");
descriptor.setExpert(false);
descriptor.setHidden(false);
descriptor.setPreferred(true);
descriptor.setValue("type", Map.class);
descriptor.setValue("resolvableAtDesignTime", Boolean.TRUE);
list.add(descriptor);
// header
descriptor = new FeatureDescriptor();
descriptor.setName("header");
descriptor.setDisplayName("header");
//descriptor.setShortDescription("");
descriptor.setExpert(false);
descriptor.setHidden(false);
descriptor.setPreferred(true);
descriptor.setValue("type", Map.class);
descriptor.setValue("resolvableAtDesignTime", Boolean.TRUE);
list.add(descriptor);
// headerValues
descriptor = new FeatureDescriptor();
descriptor.setName("headerValues");
descriptor.setDisplayName("headerValues");
//descriptor.setShortDescription("");
descriptor.setExpert(false);
descriptor.setHidden(false);
descriptor.setPreferred(true);
descriptor.setValue("type", Map.class);
descriptor.setValue("resolvableAtDesignTime", Boolean.TRUE);
list.add(descriptor);
// cookie
descriptor = new FeatureDescriptor();
descriptor.setName("cookie");
descriptor.setDisplayName("cookie");
//descriptor.setShortDescription("");
descriptor.setExpert(false);
descriptor.setHidden(false);
descriptor.setPreferred(true);
descriptor.setValue("type", Map.class);
descriptor.setValue("resolvableAtDesignTime", Boolean.TRUE);
list.add(descriptor);
// initParam
descriptor = new FeatureDescriptor();
descriptor.setName("initParam");
descriptor.setDisplayName("initParam");
//descriptor.setShortDescription("");
descriptor.setExpert(false);
descriptor.setHidden(false);
descriptor.setPreferred(true);
descriptor.setValue("type", Map.class);
descriptor.setValue("resolvableAtDesignTime", Boolean.TRUE);
list.add(descriptor);
return list.iterator();
}
/**
* If the base object is null, returns
* String.class. Otherwise, returns null.
*
* @param context The context of this evaluation.
* @param base Only null is handled by this resolver.
* Other values will result in a null return value.
* @return null if base is not null; otherwise
* String.class.
*/
public Class getCommonPropertyType(ELContext context,
Object base) {
if (base == null) {
return String.class;
}
return null;
}
// XXX - I moved this class from commons-el to an inner class here
// so that we do not have a dependency from the JSP APIs into commons-el.
// There might be a better way to do this.
/**
* This class is used to generate the implicit Map and List objects
* that wrap various elements of the PageContext. It also returns the
* correct implicit object for a given implicit object name.
*
* @author Nathan Abramson - Art Technology Group
**/
private static class ImplicitObjects
{
//-------------------------------------
// Constants
//-------------------------------------
// XXX - This probably needs to change, now that this is in a
// standard pkg.
static final String sAttributeName =
"org.apache.taglibs.standard.ImplicitObjects";
//-------------------------------------
// Member variables
//-------------------------------------
PageContext mContext;
Map mPage;
Map mRequest;
Map mSession;
Map mApplication;
Map mParam;
Map mParams;
Map mHeader;
Map mHeaders;
Map mInitParam;
Map mCookie;
//-------------------------------------
/**
*
* Constructor
**/
public ImplicitObjects (PageContext pContext)
{
mContext = pContext;
}
//-------------------------------------
/**
*
* Finds the ImplicitObjects associated with the PageContext,
* creating it if it doesn't yet exist.
**/
public static ImplicitObjects getImplicitObjects (PageContext pContext)
{
ImplicitObjects objs =
(ImplicitObjects)
pContext.getAttribute (sAttributeName,
PageContext.PAGE_SCOPE);
if (objs == null) {
objs = new ImplicitObjects (pContext);
pContext.setAttribute (sAttributeName,
objs,
PageContext.PAGE_SCOPE);
}
return objs;
}
//-------------------------------------
/**
*
* Returns the Map that "wraps" page-scoped attributes
**/
public Map getPageScopeMap ()
{
if (mPage == null) {
mPage = createPageScopeMap (mContext);
}
return mPage;
}
//-------------------------------------
/**
*
* Returns the Map that "wraps" request-scoped attributes
**/
public Map getRequestScopeMap ()
{
if (mRequest == null) {
mRequest = createRequestScopeMap (mContext);
}
return mRequest;
}
//-------------------------------------
/**
*
* Returns the Map that "wraps" session-scoped attributes
**/
public Map getSessionScopeMap ()
{
if (mSession == null) {
mSession = createSessionScopeMap (mContext);
}
return mSession;
}
//-------------------------------------
/**
*
* Returns the Map that "wraps" application-scoped attributes
**/
public Map getApplicationScopeMap ()
{
if (mApplication == null) {
mApplication = createApplicationScopeMap (mContext);
}
return mApplication;
}
//-------------------------------------
/**
*
* Returns the Map that maps parameter name to a single parameter
* values.
**/
public Map getParamMap ()
{
if (mParam == null) {
mParam = createParamMap (mContext);
}
return mParam;
}
//-------------------------------------
/**
*
* Returns the Map that maps parameter name to an array of parameter
* values.
**/
public Map getParamsMap ()
{
if (mParams == null) {
mParams = createParamsMap (mContext);
}
return mParams;
}
//-------------------------------------
/**
*
* Returns the Map that maps header name to a single header
* values.
**/
public Map getHeaderMap ()
{
if (mHeader == null) {
mHeader = createHeaderMap (mContext);
}
return mHeader;
}
//-------------------------------------
/**
*
* Returns the Map that maps header name to an array of header
* values.
**/
public Map getHeadersMap ()
{
if (mHeaders == null) {
mHeaders = createHeadersMap (mContext);
}
return mHeaders;
}
//-------------------------------------
/**
*
* Returns the Map that maps init parameter name to a single init
* parameter values.
**/
public Map getInitParamMap ()
{
if (mInitParam == null) {
mInitParam = createInitParamMap (mContext);
}
return mInitParam;
}
//-------------------------------------
/**
*
* Returns the Map that maps cookie name to the first matching
* Cookie in request.getCookies().
**/
public Map getCookieMap ()
{
if (mCookie == null) {
mCookie = createCookieMap (mContext);
}
return mCookie;
}
//-------------------------------------
// Methods for generating wrapper maps
//-------------------------------------
/**
*
* Creates the Map that "wraps" page-scoped attributes
**/
public static Map createPageScopeMap(PageContext pContext)
{
final PageContext context = pContext;
return new EnumeratedMap ()
{
public Enumeration enumerateKeys ()
{
return context.getAttributeNamesInScope
(PageContext.PAGE_SCOPE);
}
public Object getValue (Object pKey)
{
if (pKey instanceof String) {
return context.getAttribute
((String) pKey,
PageContext.PAGE_SCOPE);
}
else {
return null;
}
}
public boolean isMutable ()
{
return true;
}
};
}
//-------------------------------------
/**
*
* Creates the Map that "wraps" request-scoped attributes
**/
public static Map createRequestScopeMap (PageContext pContext)
{
final PageContext context = pContext;
return new EnumeratedMap ()
{
public Enumeration enumerateKeys ()
{
return context.getAttributeNamesInScope
(PageContext.REQUEST_SCOPE);
}
public Object getValue (Object pKey)
{
if (pKey instanceof String) {
return context.getAttribute
((String) pKey,
PageContext.REQUEST_SCOPE);
}
else {
return null;
}
}
public boolean isMutable ()
{
return true;
}
};
}
//-------------------------------------
/**
*
* Creates the Map that "wraps" session-scoped attributes
**/
public static Map createSessionScopeMap (PageContext pContext)
{
final PageContext context = pContext;
return new EnumeratedMap ()
{
public Enumeration enumerateKeys ()
{
return context.getAttributeNamesInScope
(PageContext.SESSION_SCOPE);
}
public Object getValue (Object pKey)
{
if (pKey instanceof String) {
return context.getAttribute
((String) pKey,
PageContext.SESSION_SCOPE);
}
else {
return null;
}
}
public boolean isMutable ()
{
return true;
}
};
}
//-------------------------------------
/**
*
* Creates the Map that "wraps" application-scoped attributes
**/
public static Map createApplicationScopeMap (PageContext pContext)
{
final PageContext context = pContext;
return new EnumeratedMap ()
{
public Enumeration enumerateKeys ()
{
return context.getAttributeNamesInScope
(PageContext.APPLICATION_SCOPE);
}
public Object getValue (Object pKey)
{
if (pKey instanceof String) {
return context.getAttribute
((String) pKey,
PageContext.APPLICATION_SCOPE);
}
else {
return null;
}
}
public boolean isMutable ()
{
return true;
}
};
}
//-------------------------------------
/**
*
* Creates the Map that maps parameter name to single parameter
* value.
**/
public static Map createParamMap (PageContext pContext)
{
final HttpServletRequest request =
(HttpServletRequest) pContext.getRequest ();
return new EnumeratedMap ()
{
public Enumeration enumerateKeys ()
{
return request.getParameterNames ();
}
public String getValue (Object pKey)
{
if (pKey instanceof String) {
return request.getParameter ((String) pKey);
}
else {
return null;
}
}
public boolean isMutable ()
{
return false;
}
};
}
//-------------------------------------
/**
*
* Creates the Map that maps parameter name to an array of parameter
* values.
**/
public static Map createParamsMap (PageContext pContext)
{
final HttpServletRequest request =
(HttpServletRequest) pContext.getRequest ();
return new EnumeratedMap ()
{
public Enumeration enumerateKeys ()
{
return request.getParameterNames ();
}
public String[] getValue (Object pKey)
{
if (pKey instanceof String) {
return request.getParameterValues ((String) pKey);
}
else {
return null;
}
}
public boolean isMutable ()
{
return false;
}
};
}
//-------------------------------------
/**
*
* Creates the Map that maps header name to single header
* value.
**/
public static Map createHeaderMap (PageContext pContext)
{
final HttpServletRequest request =
(HttpServletRequest) pContext.getRequest ();
return new EnumeratedMap ()
{
public Enumeration enumerateKeys ()
{
return request.getHeaderNames ();
}
public String getValue (Object pKey)
{
if (pKey instanceof String) {
return request.getHeader ((String) pKey);
}
else {
return null;
}
}
public boolean isMutable ()
{
return false;
}
};
}
//-------------------------------------
/**
*
* Creates the Map that maps header name to an array of header
* values.
**/
public static Map createHeadersMap (PageContext pContext)
{
final HttpServletRequest request =
(HttpServletRequest) pContext.getRequest ();
return new EnumeratedMap ()
{
public Enumeration enumerateKeys ()
{
return request.getHeaderNames ();
}
public String[] getValue (Object pKey)
{
if (pKey instanceof String) {
// Drain the header enumeration
List l = new ArrayList ();
Enumeration e = request.getHeaders ((String) pKey);
if (e != null) {
while (e.hasMoreElements ()) {
l.add (e.nextElement ());
}
}
return l.toArray (new String [l.size ()]);
}
else {
return null;
}
}
public boolean isMutable ()
{
return false;
}
};
}
//-------------------------------------
/**
*
* Creates the Map that maps init parameter name to single init
* parameter value.
**/
public static Map createInitParamMap(PageContext pContext)
{
final ServletContext context = pContext.getServletContext ();
return new EnumeratedMap ()
{
public Enumeration enumerateKeys ()
{
return context.getInitParameterNames ();
}
public String getValue (Object pKey)
{
if (pKey instanceof String) {
return context.getInitParameter ((String) pKey);
}
else {
return null;
}
}
public boolean isMutable ()
{
return false;
}
};
}
//-------------------------------------
/**
*
* Creates the Map that maps cookie name to the first matching
* Cookie in request.getCookies().
**/
public static Map createCookieMap (PageContext pContext)
{
// Read all the cookies and construct the entire map
HttpServletRequest request = (HttpServletRequest) pContext.getRequest ();
Cookie [] cookies = request.getCookies ();
Map ret = new HashMap ();
for (int i = 0; cookies != null && i < cookies.length; i++) {
Cookie cookie = cookies [i];
if (cookie != null) {
String name = cookie.getName ();
if (!ret.containsKey (name)) {
ret.put (name, cookie);
}
}
}
return ret;
}
//-------------------------------------
}
// XXX - I moved this class from commons-el to an inner class here
// so that we do not have a dependency from the JSP APIs into commons-el.
// There might be a better way to do this.
/**
* This is a Map implementation driven by a data source that only
* provides an enumeration of keys and a getValue(key) method. This
* class must be subclassed to implement those methods.
*
*
Some of the methods may incur a performance penalty that
* involves enumerating the entire data source. In these cases, the
* Map will try to save the results of that enumeration, but only if
* the underlying data source is immutable.
*
* @author Nathan Abramson - Art Technology Group
**/
private static abstract class EnumeratedMap
implements Map
{
//-------------------------------------
// Member variables
//-------------------------------------
Map mMap;
//-------------------------------------
public void clear ()
{
throw new UnsupportedOperationException ();
}
//-------------------------------------
public boolean containsKey (Object pKey)
{
return getValue (pKey) != null;
}
//-------------------------------------
public boolean containsValue (Object pValue)
{
return getAsMap ().containsValue (pValue);
}
//-------------------------------------
public Set> entrySet ()
{
return getAsMap ().entrySet ();
}
//-------------------------------------
public V get (Object pKey)
{
return getValue (pKey);
}
//-------------------------------------
public boolean isEmpty ()
{
return !enumerateKeys ().hasMoreElements ();
}
//-------------------------------------
public Set keySet ()
{
return getAsMap ().keySet ();
}
//-------------------------------------
public V put (K pKey, V pValue)
{
throw new UnsupportedOperationException ();
}
//-------------------------------------
public void putAll (Map pMap)
{
throw new UnsupportedOperationException ();
}
//-------------------------------------
public V remove (Object pKey)
{
throw new UnsupportedOperationException ();
}
//-------------------------------------
public int size ()
{
return getAsMap ().size ();
}
//-------------------------------------
public Collection values ()
{
return getAsMap ().values ();
}
//-------------------------------------
// Abstract methods
//-------------------------------------
/**
*
* Returns an enumeration of the keys
**/
public abstract Enumeration enumerateKeys ();
//-------------------------------------
/**
*
* Returns true if it is possible for this data source to change
**/
public abstract boolean isMutable ();
//-------------------------------------
/**
*
* Returns the value associated with the given key, or null if not
* found.
**/
public abstract V getValue (Object pKey);
//-------------------------------------
/**
*
* Converts the MapSource to a Map. If the map is not mutable, this
* is cached
**/
public Map getAsMap ()
{
if (mMap != null) {
return mMap;
}
else {
Map m = convertToMap ();
if (!isMutable ()) {
mMap = m;
}
return m;
}
}
//-------------------------------------
/**
*
* Converts to a Map
**/
Map convertToMap ()
{
Map ret = new HashMap ();
for (Enumeration e = enumerateKeys (); e.hasMoreElements (); ) {
K key = e.nextElement ();
V value = getValue (key);
ret.put (key, value);
}
return ret;
}
//-------------------------------------
}
}