org.metawidget.jsp.JspUtils Maven / Gradle / Ivy
// Metawidget
//
// This file is dual licensed under both the LGPL
// (http://www.gnu.org/licenses/lgpl-2.1.html) and the EPL
// (http://www.eclipse.org/org/documents/epl-v10.php). As a
// recipient of Metawidget, you may choose to receive it under either
// the LGPL or the EPL.
//
// Commercial licenses are also available. See http://metawidget.org
// for details.
package org.metawidget.jsp;
import java.io.IOException;
import java.io.PrintWriter;
import java.io.Reader;
import java.io.StringReader;
import java.io.StringWriter;
import java.io.Writer;
import java.util.Enumeration;
import java.util.List;
import java.util.regex.Pattern;
import javax.servlet.Servlet;
import javax.servlet.ServletConfig;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpSession;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspWriter;
import javax.servlet.jsp.PageContext;
import javax.servlet.jsp.el.ExpressionEvaluator;
import javax.servlet.jsp.el.VariableResolver;
import javax.servlet.jsp.tagext.BodyContent;
import javax.servlet.jsp.tagext.BodyTag;
import javax.servlet.jsp.tagext.IterationTag;
import javax.servlet.jsp.tagext.Tag;
import javax.servlet.jsp.tagext.TagSupport;
import org.metawidget.util.CollectionUtils;
/**
* Utilities for working with JSPs.
*
* @author Richard Kennard
*/
public final class JspUtils {
//
// Public statics
//
/**
* @return true if the given HTML consists of nothing but hidden fields
*/
public static boolean isJustHiddenFields( CharSequence html ) {
return PATTERN_HIDDEN_FIELDS.matcher( html ).matches();
}
/**
* Writes the given Tag to a String (not its usual pageContext.getOut).
*/
public static String writeTag( PageContext context, Tag tag, Tag parentTag )
throws JspException {
PageContextDelegate delegateContext = new PageContextDelegate( context );
writeTagInternal( delegateContext, tag, parentTag );
return delegateContext.getOut().toString();
}
/**
* Simulates adding the given child Tag to the given parent Tag.
*
* Whilst the JSP component model provides findAncestorWithClass to allow Tags to
* find their parent, there is no mechanism for programmatically adding children to a Tag. This
* is a problem for Metawidget, which needs to be able to build Tags, separately process them,
* and then render them.
*
* This method provides a way to defer the rendering of a child, to give us chance to process
* it.
*/
public static void addDeferredChild( TagSupport parentTag, Tag childTag ) {
@SuppressWarnings( "unchecked" )
List deferredChildren = (List) parentTag.getValue( DEFERRED_CHILD_KEY );
if ( deferredChildren == null ) {
deferredChildren = CollectionUtils.newArrayList();
parentTag.setValue( DEFERRED_CHILD_KEY, deferredChildren );
}
deferredChildren.add( childTag );
}
public static void setBodyContent( BodyTag tag, String content ) {
try {
BufferedContent bodyContent = new BufferedContent();
bodyContent.write( content );
tag.setBodyContent( bodyContent );
} catch( IOException e ) {
throw new RuntimeException( e );
}
}
//
// Private statics
//
private static final String DEFERRED_CHILD_KEY = JspUtils.class + ".DEFERRED_CHILD";
private static void writeTagInternal( PageContext context, Tag tag, Tag parentTag )
throws JspException {
tag.setPageContext( context );
tag.setParent( parentTag );
try {
int returnCode = tag.doStartTag();
if ( returnCode != Tag.SKIP_BODY ) {
// doInitBody
if ( tag instanceof BodyTag ) {
( (BodyTag) tag ).doInitBody();
}
// Support deferred children
if ( tag instanceof TagSupport ) {
@SuppressWarnings( "unchecked" )
List deferredChildren = (List) ( (TagSupport) tag ).getValue( DEFERRED_CHILD_KEY );
if ( deferredChildren != null ) {
for ( Tag childTag : deferredChildren ) {
writeTagInternal( context, childTag, tag );
}
}
}
// doAfterBody
if ( tag instanceof IterationTag ) {
returnCode = IterationTag.EVAL_BODY_AGAIN;
while ( returnCode == IterationTag.EVAL_BODY_AGAIN ) {
returnCode = ( (IterationTag) tag ).doAfterBody();
}
}
}
tag.doEndTag();
} finally {
tag.release();
}
}
//
// Inner class
//
/**
* Subverts the getOut method of a PageContext to use
* BufferedContent.
*/
private static class PageContextDelegate
extends PageContext {
//
// Private members
//
private PageContext mContext;
private JspWriter mWriter;
//
// Constructor
//
public PageContextDelegate( PageContext context ) {
mContext = context;
mWriter = new BufferedContent();
}
//
// Public methods
//
@Override
public JspWriter getOut() {
return mWriter;
}
//
// Delegate methods
//
@Override
public Object findAttribute( String attribute ) {
return mContext.findAttribute( attribute );
}
@Override
public void forward( String relativeUrlPath )
throws ServletException, IOException {
mContext.forward( relativeUrlPath );
}
@Override
public Object getAttribute( String name, int scope ) {
return mContext.getAttribute( name, scope );
}
@Override
public Object getAttribute( String name ) {
return mContext.getAttribute( name );
}
@Override
public Enumeration getAttributeNamesInScope( int scope ) {
return mContext.getAttributeNamesInScope( scope );
}
@Override
public int getAttributesScope( String name ) {
return mContext.getAttributesScope( name );
}
@Override
public Exception getException() {
return mContext.getException();
}
@Override
public ExpressionEvaluator getExpressionEvaluator() {
return mContext.getExpressionEvaluator();
}
@Override
public Object getPage() {
return mContext.getPage();
}
@Override
public ServletRequest getRequest() {
return mContext.getRequest();
}
@Override
public ServletResponse getResponse() {
return mContext.getResponse();
}
@Override
public ServletConfig getServletConfig() {
return mContext.getServletConfig();
}
@Override
public ServletContext getServletContext() {
return mContext.getServletContext();
}
@Override
public HttpSession getSession() {
return mContext.getSession();
}
@Override
public VariableResolver getVariableResolver() {
return mContext.getVariableResolver();
}
@Override
public void handlePageException( Exception exception )
throws ServletException, IOException {
mContext.handlePageException( exception );
}
@Override
public void handlePageException( Throwable throwable )
throws ServletException, IOException {
mContext.handlePageException( throwable );
}
@Override
public void include( String relativeUrlPath, boolean flush )
throws ServletException, IOException {
mContext.include( relativeUrlPath, flush );
}
@Override
public void include( String relativeUrlPath )
throws ServletException, IOException {
mContext.include( relativeUrlPath );
}
@Override
public void initialize( Servlet servlet, ServletRequest request, ServletResponse response, String errorPageUrl, boolean needsSession, int bufferSize, boolean autoFlush )
throws IOException {
mContext.initialize( servlet, request, response, errorPageUrl, needsSession, bufferSize, autoFlush );
}
@Override
public void release() {
mContext.release();
}
@Override
public void removeAttribute( String name, int scope ) {
mContext.removeAttribute( name, scope );
}
@Override
public void removeAttribute( String name ) {
mContext.removeAttribute( name );
}
@Override
public void setAttribute( String name, Object value, int scope ) {
mContext.setAttribute( name, value, scope );
}
@Override
public void setAttribute( String name, Object value ) {
mContext.setAttribute( name, value );
}
}
/**
* Acts as a buffer for BodyContent. Allows Tag output to be buffered
* temporarily before deciding whether to use it or discard it.
*
* Since BodyContent extends JspWriter, acts as a buffer for
* JspWriter too.
*/
private static class BufferedContent
extends BodyContent {
//
// Private members
//
private StringWriter mStringWriter;
private PrintWriter mPrintWriter;
//
// Constructor
//
public BufferedContent() {
super( null );
clear();
}
//
// Public methods
//
@Override
public void clear() {
mStringWriter = new StringWriter();
mPrintWriter = new PrintWriter( mStringWriter );
}
@Override
public void clearBuffer() {
// Do nothing
}
@Override
public void close() {
mPrintWriter.close();
}
@Override
public void flush() {
mPrintWriter.flush();
}
@Override
public int getRemaining() {
return 0;
}
@Override
public void newLine() {
mPrintWriter.println();
}
@Override
public void print( boolean value ) {
mPrintWriter.print( value );
}
@Override
public void print( char value ) {
mPrintWriter.print( value );
}
@Override
public void print( int value ) {
mPrintWriter.print( value );
}
@Override
public void print( long value ) {
mPrintWriter.print( value );
}
@Override
public void print( float value ) {
mPrintWriter.print( value );
}
@Override
public void print( double value ) {
mPrintWriter.print( value );
}
@Override
public void print( char[] value ) {
mPrintWriter.print( value );
}
@Override
public void print( String value ) {
mPrintWriter.print( value );
}
@Override
public void print( Object value ) {
mPrintWriter.print( value );
}
@Override
public void println() {
mPrintWriter.println();
}
@Override
public void println( boolean value ) {
mPrintWriter.println( value );
}
@Override
public void println( char value ) {
mPrintWriter.println( value );
}
@Override
public void println( int value ) {
mPrintWriter.println( value );
}
@Override
public void println( long value ) {
mPrintWriter.println( value );
}
@Override
public void println( float value ) {
mPrintWriter.println( value );
}
@Override
public void println( double value ) {
mPrintWriter.println( value );
}
@Override
public void println( char[] value ) {
mPrintWriter.println( value );
}
@Override
public void println( String value ) {
mPrintWriter.println( value );
}
@Override
public void println( Object value ) {
mPrintWriter.println( value );
}
@Override
public void write( char[] cbuf, int off, int len ) {
mPrintWriter.write( cbuf, off, len );
}
@Override
public String toString() {
return getString();
}
@Override
public Reader getReader() {
return new StringReader( getString() );
}
@Override
public String getString() {
return mStringWriter.toString();
}
@Override
public void writeOut( Writer writer )
throws IOException {
writer.write( getString() );
}
}
//
// Private statics
//
private static final Pattern PATTERN_HIDDEN_FIELDS = Pattern.compile( "(\\s*<\\s*(input)\\s+[^>]*?(type)\\s*=\\s*\"\\s*hidden\\s*\"[^>]*?>\\s*)+?" );
//
// Private constructor
//
private JspUtils() {
// Can never be called
}
}