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Struts example source code file (PageDataImpl.java)

This example Struts source code file (PageDataImpl.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Struts tags/keywords

attributes, cdata, cdata, chararraywriter, compiler, firstpassvisitor, io, jasperexception, jasperexception, jsp, sax, servlet, string, string, stringbuffer, tagconstants, utf-8, utf-8, util

The Struts PageDataImpl.java source code

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.struts2.jasper.compiler;

import java.io.InputStream;
import java.io.ByteArrayInputStream;
import java.io.CharArrayWriter;
import java.io.UnsupportedEncodingException;
import java.util.ListIterator;
import javax.servlet.jsp.tagext.PageData;
import org.xml.sax.Attributes;
import org.xml.sax.helpers.AttributesImpl;
import org.apache.struts2.jasper.JasperException;

/**
 * An implementation of <tt>javax.servlet.jsp.tagext.PageData which
 * builds the XML view of a given page.
 *
 * The XML view is built in two passes:
 *
 * During the first pass, the FirstPassVisitor collects the attributes of the
 * top-level jsp:root and those of the jsp:root elements of any included
 * pages, and adds them to the jsp:root element of the XML view.
 * In addition, any taglib directives are converted into xmlns: attributes and
 * added to the jsp:root element of the XML view.
 * This pass ignores any nodes other than JspRoot and TaglibDirective.
 *
 * During the second pass, the SecondPassVisitor produces the XML view, using
 * the combined jsp:root attributes determined in the first pass and any
 * remaining pages nodes (this pass ignores any JspRoot and TaglibDirective
 * nodes).
 *
 * @author Jan Luehe
 */
class PageDataImpl extends PageData implements TagConstants {

    private static final String JSP_VERSION = "2.0";
    private static final String CDATA_START_SECTION = "<![CDATA[\n";
    private static final String CDATA_END_SECTION = "]]>\n";

    // string buffer used to build XML view
    private StringBuffer buf;

    /**
     * Constructor.
     *
     * @param page the page nodes from which to generate the XML view
     */
    public PageDataImpl(Node.Nodes page, Compiler compiler)
	        throws JasperException {

	// First pass
	FirstPassVisitor firstPass = new FirstPassVisitor(page.getRoot(),
							  compiler.getPageInfo());
	page.visit(firstPass);

	// Second pass
	buf = new StringBuffer();
	SecondPassVisitor secondPass
	    = new SecondPassVisitor(page.getRoot(), buf, compiler,
				    firstPass.getJspIdPrefix());
	page.visit(secondPass);
    }

    /**
     * Returns the input stream of the XML view.
     *
     * @return the input stream of the XML view
     */
    public InputStream getInputStream() {
	// Turn StringBuffer into InputStream
        try {
            return new ByteArrayInputStream(buf.toString().getBytes("UTF-8"));
        } catch (UnsupportedEncodingException uee) {
	    // should never happen
            throw new RuntimeException(uee.toString());
        }
    }

    /*
     * First-pass Visitor for JspRoot nodes (representing jsp:root elements)
     * and TablibDirective nodes, ignoring any other nodes.
     *
     * The purpose of this Visitor is to collect the attributes of the
     * top-level jsp:root and those of the jsp:root elements of any included
     * pages, and add them to the jsp:root element of the XML view.
     * In addition, this Visitor converts any taglib directives into xmlns:
     * attributes and adds them to the jsp:root element of the XML view.
     */
    static class FirstPassVisitor
	        extends Node.Visitor implements TagConstants {

	private Node.Root root;
	private AttributesImpl rootAttrs;
	private PageInfo pageInfo;

	// Prefix for the 'id' attribute
	private String jspIdPrefix;

	/*
	 * Constructor
	 */
	public FirstPassVisitor(Node.Root root, PageInfo pageInfo) {
	    this.root = root;
	    this.pageInfo = pageInfo;
	    this.rootAttrs = new AttributesImpl();
	    this.rootAttrs.addAttribute("", "", "version", "CDATA",
					JSP_VERSION);
	    this.jspIdPrefix = "jsp";
	}

	public void visit(Node.Root n) throws JasperException {
	    visitBody(n);
	    if (n == root) {
		/*
		 * Top-level page.
		 *
		 * Add
		 *   xmlns:jsp="http://java.sun.com/JSP/Page"
		 * attribute only if not already present.
		 */
		if (!JSP_URI.equals(rootAttrs.getValue("xmlns:jsp"))) {
		    rootAttrs.addAttribute("", "", "xmlns:jsp", "CDATA",
					   JSP_URI);
		}

		if (pageInfo.isJspPrefixHijacked()) {
		    /*
		     * 'jsp' prefix has been hijacked, that is, bound to a
		     * namespace other than the JSP namespace. This means that
		     * when adding an 'id' attribute to each element, we can't
		     * use the 'jsp' prefix. Therefore, create a new prefix 
		     * (one that is unique across the translation unit) for use
		     * by the 'id' attribute, and bind it to the JSP namespace
		     */
		    jspIdPrefix += "jsp";
		    while (pageInfo.containsPrefix(jspIdPrefix)) {
			jspIdPrefix += "jsp";
		    }
		    rootAttrs.addAttribute("", "", "xmlns:" + jspIdPrefix,
					   "CDATA", JSP_URI);
		}

		root.setAttributes(rootAttrs);
	    }
	}

	public void visit(Node.JspRoot n) throws JasperException {
	    addAttributes(n.getTaglibAttributes());
            addAttributes(n.getNonTaglibXmlnsAttributes());
	    addAttributes(n.getAttributes());

	    visitBody(n);
	}

	/*
	 * Converts taglib directive into "xmlns:..." attribute of jsp:root
	 * element.
	 */
	public void visit(Node.TaglibDirective n) throws JasperException {
	    Attributes attrs = n.getAttributes();
	    if (attrs != null) {
		String qName = "xmlns:" + attrs.getValue("prefix");
		/*
		 * According to javadocs of org.xml.sax.helpers.AttributesImpl,
		 * the addAttribute method does not check to see if the
		 * specified attribute is already contained in the list: This
		 * is the application's responsibility!
		 */
		if (rootAttrs.getIndex(qName) == -1) {
		    String location = attrs.getValue("uri");
		    if (location != null) {
                        if (location.startsWith("/")) {
                            location = URN_JSPTLD + location;
                        }
			rootAttrs.addAttribute("", "", qName, "CDATA",
					       location);
		    } else {
			location = attrs.getValue("tagdir");
			rootAttrs.addAttribute("", "", qName, "CDATA",
					       URN_JSPTAGDIR + location);
		    }
		}
	    }
	}

	public String getJspIdPrefix() {
	    return jspIdPrefix;
	}

	private void addAttributes(Attributes attrs) {
	    if (attrs != null) {
		int len = attrs.getLength();

		for (int i=0; i<len; i++) {
                    String qName = attrs.getQName(i);
		    if ("version".equals(qName)) {
			continue;
		    }

                    // Bugzilla 35252: http://issues.apache.org/bugzilla/show_bug.cgi?id=35252
                    if(rootAttrs.getIndex(qName) == -1) {
                        rootAttrs.addAttribute(attrs.getURI(i),
                                               attrs.getLocalName(i),
                                               qName,
                                               attrs.getType(i),
                                               attrs.getValue(i));
                    }
		}
	    }
	}
    }


    /*
     * Second-pass Visitor responsible for producing XML view and assigning
     * each element a unique jsp:id attribute.
     */
    static class SecondPassVisitor extends Node.Visitor
        	implements TagConstants {

	private Node.Root root;
	private StringBuffer buf;
	private Compiler compiler;
	private String jspIdPrefix;
	private boolean resetDefaultNS = false;

	// Current value of jsp:id attribute
	private int jspId;

	/*
	 * Constructor
	 */
	public SecondPassVisitor(Node.Root root, StringBuffer buf,
				 Compiler compiler, String jspIdPrefix) {
	    this.root = root;
	    this.buf = buf;
	    this.compiler = compiler;
	    this.jspIdPrefix = jspIdPrefix;
	}

	/*
	 * Visits root node.
	 */
	public void visit(Node.Root n) throws JasperException {
	    if (n == this.root) {
		// top-level page
		appendXmlProlog();
		appendTag(n);
	    } else {
		boolean resetDefaultNSSave = resetDefaultNS;
		if (n.isXmlSyntax()) {
		    resetDefaultNS = true;
		}
		visitBody(n);
		resetDefaultNS = resetDefaultNSSave;
	    }
	}

	/*
	 * Visits jsp:root element of JSP page in XML syntax.
	 *
	 * Any nested jsp:root elements (from pages included via an
	 * include directive) are ignored.
	 */
	public void visit(Node.JspRoot n) throws JasperException {
	    visitBody(n);
	}

	public void visit(Node.PageDirective n) throws JasperException {
	    appendPageDirective(n);
	}

	public void visit(Node.IncludeDirective n) throws JasperException {
	    // expand in place
	    visitBody(n);
	}

	public void visit(Node.Comment n) throws JasperException {
	    // Comments are ignored in XML view
	}

	public void visit(Node.Declaration n) throws JasperException {
	    appendTag(n);
	}

	public void visit(Node.Expression n) throws JasperException {
	    appendTag(n);
	}

	public void visit(Node.Scriptlet n) throws JasperException {
	    appendTag(n);
	}

	public void visit(Node.JspElement n) throws JasperException {
	    appendTag(n);
	}

	public void visit(Node.ELExpression n) throws JasperException {
	    if (!n.getRoot().isXmlSyntax()) {
		buf.append("<").append(JSP_TEXT_ACTION);
		buf.append(" ");
	        buf.append(jspIdPrefix);
		buf.append(":id=\"");
		buf.append(jspId++).append("\">");
	    }
	    buf.append("${");
            buf.append(JspUtil.escapeXml(n.getText()));
	    buf.append("}");
	    if (!n.getRoot().isXmlSyntax()) {
		buf.append(JSP_TEXT_ACTION_END);
	    }
	    buf.append("\n");
	}

	public void visit(Node.IncludeAction n) throws JasperException {
	    appendTag(n);
	}
    
	public void visit(Node.ForwardAction n) throws JasperException {
	    appendTag(n);
	}

	public void visit(Node.GetProperty n) throws JasperException {
	    appendTag(n);
	}

	public void visit(Node.SetProperty n) throws JasperException {
	    appendTag(n);
	}

	public void visit(Node.ParamAction n) throws JasperException {
	    appendTag(n);
	}

	public void visit(Node.ParamsAction n) throws JasperException {
	    appendTag(n);
	}

	public void visit(Node.FallBackAction n) throws JasperException {
	    appendTag(n);
	}

	public void visit(Node.UseBean n) throws JasperException {
	    appendTag(n);
	}
	
	public void visit(Node.PlugIn n) throws JasperException {
	    appendTag(n);
	}

        public void visit(Node.NamedAttribute n) throws JasperException {
            appendTag(n);
        }
        
        public void visit(Node.JspBody n) throws JasperException {
            appendTag(n);
        }

	public void visit(Node.CustomTag n) throws JasperException {
	    boolean resetDefaultNSSave = resetDefaultNS;
	    appendTag(n, resetDefaultNS);
	    resetDefaultNS = resetDefaultNSSave;
	}

	public void visit(Node.UninterpretedTag n) throws JasperException {
	    boolean resetDefaultNSSave = resetDefaultNS;
	    appendTag(n, resetDefaultNS);
	    resetDefaultNS = resetDefaultNSSave;
	}

	public void visit(Node.JspText n) throws JasperException {
	    appendTag(n);
	}

	public void visit(Node.DoBodyAction n) throws JasperException {
	    appendTag(n);
	}

        public void visit(Node.InvokeAction n) throws JasperException {
	    appendTag(n);
	}

	public void visit(Node.TagDirective n) throws JasperException {
	    appendTagDirective(n);
	}

	public void visit(Node.AttributeDirective n) throws JasperException {
	    appendTag(n);
	}

	public void visit(Node.VariableDirective n) throws JasperException {
	    appendTag(n);
	}
        
	public void visit(Node.TemplateText n) throws JasperException {
	    /*
	     * If the template text came from a JSP page written in JSP syntax,
	     * create a jsp:text element for it (JSP 5.3.2).
	     */
	    appendText(n.getText(), !n.getRoot().isXmlSyntax());
	}

	/*
	 * Appends the given tag, including its body, to the XML view.
	 */
	private void appendTag(Node n) throws JasperException {
	    appendTag(n, false);
	}

	/*
	 * Appends the given tag, including its body, to the XML view,
	 * and optionally reset default namespace to "", if none specified.
	 */
	private void appendTag(Node n, boolean addDefaultNS)
		throws JasperException {

	    Node.Nodes body = n.getBody();
	    String text = n.getText();

	    buf.append("<").append(n.getQName());
	    buf.append("\n");

	    printAttributes(n, addDefaultNS);
	    buf.append("  ").append(jspIdPrefix).append(":id").append("=\"");
	    buf.append(jspId++).append("\"\n");

	    if (ROOT_ACTION.equals(n.getLocalName()) || body != null
		        || text != null) {
		buf.append(">\n");
		if (ROOT_ACTION.equals(n.getLocalName())) {
		    if (compiler.getCompilationContext().isTagFile()) {
			appendTagDirective();
		    } else {
			appendPageDirective();
		    }
		}
		if (body != null) {
		    body.visit(this);
		} else {
		    appendText(text, false);
		}
		buf.append("</" + n.getQName() + ">\n");
	    } else {
		buf.append("/>\n");
	    }
	}

	/*
	 * Appends the page directive with the given attributes to the XML
	 * view.
	 *
	 * Since the import attribute of the page directive is the only page
	 * attribute that is allowed to appear multiple times within the same
	 * document, and since XML allows only single-value attributes,
	 * the values of multiple import attributes must be combined into one,
	 * separated by comma.
	 *
	 * If the given page directive contains just 'contentType' and/or
	 * 'pageEncoding' attributes, we ignore it, as we've already appended
	 * a page directive containing just these two attributes.
	 */
	private void appendPageDirective(Node.PageDirective n) {
	    boolean append = false;
	    Attributes attrs = n.getAttributes();
	    int len = (attrs == null) ? 0 : attrs.getLength();
	    for (int i=0; i<len; i++) {
		String attrName = attrs.getQName(i);
		if (!"pageEncoding".equals(attrName)
		        && !"contentType".equals(attrName)) {
		    append = true;
		    break;
		}
	    }
	    if (!append) {
		return;
	    }

	    buf.append("<").append(n.getQName());
	    buf.append("\n");

	    // append jsp:id
	    buf.append("  ").append(jspIdPrefix).append(":id").append("=\"");
	    buf.append(jspId++).append("\"\n");

	    // append remaining attributes
	    for (int i=0; i<len; i++) {
		String attrName = attrs.getQName(i);
		if ("import".equals(attrName) || "contentType".equals(attrName)
		        || "pageEncoding".equals(attrName)) {
		    /*
		     * Page directive's 'import' attribute is considered
		     * further down, and its 'pageEncoding' and 'contentType'
		     * attributes are ignored, since we've already appended
		     * a new page directive containing just these two
		     * attributes
		     */
		    continue;
		}
		String value = attrs.getValue(i);
		buf.append("  ").append(attrName).append("=\"");
		buf.append(JspUtil.getExprInXml(value)).append("\"\n");
	    }
	    if (n.getImports().size() > 0) {
		// Concatenate names of imported classes/packages
		boolean first = true;
		ListIterator iter = n.getImports().listIterator();
		while (iter.hasNext()) {
		    if (first) {
			first = false;
			buf.append("  import=\"");
		    } else {
			buf.append(",");
		    }
		    buf.append(JspUtil.getExprInXml((String) iter.next()));
		}
		buf.append("\"\n");
	    }
	    buf.append("/>\n");
	}

	/*
	 * Appends a page directive with 'pageEncoding' and 'contentType'
	 * attributes.
	 *
	 * The value of the 'pageEncoding' attribute is hard-coded
	 * to UTF-8, whereas the value of the 'contentType' attribute, which
	 * is identical to what the container will pass to
	 * ServletResponse.setContentType(), is derived from the pageInfo.
	 */
	private void appendPageDirective() {
	    buf.append("<").append(JSP_PAGE_DIRECTIVE_ACTION);
	    buf.append("\n");

	    // append jsp:id
	    buf.append("  ").append(jspIdPrefix).append(":id").append("=\"");
	    buf.append(jspId++).append("\"\n");
	    buf.append("  ").append("pageEncoding").append("=\"UTF-8\"\n");
	    buf.append("  ").append("contentType").append("=\"");
	    buf.append(compiler.getPageInfo().getContentType()).append("\"\n");
	    buf.append("/>\n");	    
	}

	/*
	 * Appends the tag directive with the given attributes to the XML
	 * view.
	 *
	 * If the given tag directive contains just a 'pageEncoding'
	 * attributes, we ignore it, as we've already appended
	 * a tag directive containing just this attributes.
	 */
	private void appendTagDirective(Node.TagDirective n)
	        throws JasperException {

	    boolean append = false;
	    Attributes attrs = n.getAttributes();
	    int len = (attrs == null) ? 0 : attrs.getLength();
	    for (int i=0; i<len; i++) {
		String attrName = attrs.getQName(i);
		if (!"pageEncoding".equals(attrName)) {
		    append = true;
		    break;
		}
	    }
	    if (!append) {
		return;
	    }

	    appendTag(n);
	}

	/*
	 * Appends a tag directive containing a single 'pageEncoding'
	 * attribute whose value is hard-coded to UTF-8.
	 */
	private void appendTagDirective() {
	    buf.append("<").append(JSP_TAG_DIRECTIVE_ACTION);
	    buf.append("\n");

	    // append jsp:id
	    buf.append("  ").append(jspIdPrefix).append(":id").append("=\"");
	    buf.append(jspId++).append("\"\n");
	    buf.append("  ").append("pageEncoding").append("=\"UTF-8\"\n");
	    buf.append("/>\n");	    
	}

	private void appendText(String text, boolean createJspTextElement) {
	    if (createJspTextElement) {
		buf.append("<").append(JSP_TEXT_ACTION);
		buf.append("\n");

		// append jsp:id
		buf.append("  ").append(jspIdPrefix).append(":id").append("=\"");
		buf.append(jspId++).append("\"\n");
		buf.append(">\n");

		appendCDATA(text);
		buf.append(JSP_TEXT_ACTION_END);
		buf.append("\n");
	    } else {
		appendCDATA(text);
	    }
	}
	
	/*
	 * Appends the given text as a CDATA section to the XML view, unless
	 * the text has already been marked as CDATA.
	 */
	private void appendCDATA(String text) {
	    buf.append(CDATA_START_SECTION);
	    buf.append(escapeCDATA(text));
	    buf.append(CDATA_END_SECTION);
	}

	/*
	 * Escapes any occurrences of "]]>" (by replacing them with "]]>")
	 * within the given text, so it can be included in a CDATA section.
	 */
	private String escapeCDATA(String text) {
            if( text==null ) return "";
	    int len = text.length();
	    CharArrayWriter result = new CharArrayWriter(len);
	    for (int i=0; i<len; i++) {
		if (((i+2) < len)
		        && (text.charAt(i) == ']')
		        && (text.charAt(i+1) == ']')
		        && (text.charAt(i+2) == '>')) {
		    // match found
		    result.write(']');
		    result.write(']');
		    result.write('&');
		    result.write('g');
		    result.write('t');
		    result.write(';');
		    i += 2;
		} else {
		    result.write(text.charAt(i));
		}
	    }
	    return result.toString();
	}

	/*
	 * Appends the attributes of the given Node to the XML view.
	 */
	private void printAttributes(Node n, boolean addDefaultNS) {

	    /*
	     * Append "xmlns" attributes that represent tag libraries
	     */
	    Attributes attrs = n.getTaglibAttributes();
	    int len = (attrs == null) ? 0 : attrs.getLength();
	    for (int i=0; i<len; i++) {
		String name = attrs.getQName(i);
		String value = attrs.getValue(i);
		buf.append("  ").append(name).append("=\"").append(value).append("\"\n");
	    }

	    /*
	     * Append "xmlns" attributes that do not represent tag libraries
	     */
	    attrs = n.getNonTaglibXmlnsAttributes();
	    len = (attrs == null) ? 0 : attrs.getLength();
	    boolean defaultNSSeen = false;
	    for (int i=0; i<len; i++) {
		String name = attrs.getQName(i);
		String value = attrs.getValue(i);
		buf.append("  ").append(name).append("=\"").append(value).append("\"\n");
		defaultNSSeen |= "xmlns".equals(name);
	    }
	    if (addDefaultNS && !defaultNSSeen) {
		buf.append("  xmlns=\"\"\n");
	    }
	    resetDefaultNS = false;

	    /*
	     * Append all other attributes
	     */
	    attrs = n.getAttributes();
	    len = (attrs == null) ? 0 : attrs.getLength();
	    for (int i=0; i<len; i++) {
		String name = attrs.getQName(i);
		String value = attrs.getValue(i);
		buf.append("  ").append(name).append("=\"");
		buf.append(JspUtil.getExprInXml(value)).append("\"\n");
	    }
	}

	/*
	 * Appends XML prolog with encoding declaration.
	 */
	private void appendXmlProlog() {
	    buf.append("<?xml version=\"1.0\" encoding=\"UTF-8\" ?>\n");
	}
    }
}

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