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package org.apache.taglibs.standard.tag.common.core;
import java.io.IOException;
import java.io.Reader;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspWriter;
import javax.servlet.jsp.PageContext;
import javax.servlet.jsp.tagext.BodyTagSupport;
/**
* <p>Support for handlers of the <out> tag, which simply evalutes and
* prints the result of the expression it's passed. If the result is
* null, we print the value of the 'default' attribute's expression or
* our body (which two are mutually exclusive, although this constraint
* is enforced outside this handler, in our TagLibraryValidator).</p>
*
* @author Shawn Bayern
*/
public class OutSupport extends BodyTagSupport {
/*
* (One almost wishes XML and JSP could support "anonymous tags,"
* given the amount of trouble we had naming this one!) :-) - sb
*/
//*********************************************************************
// Internal state
protected Object value; // tag attribute
protected String def; // tag attribute
protected boolean escapeXml; // tag attribute
private boolean needBody; // non-space body needed?
//*********************************************************************
// Construction and initialization
/**
* Constructs a new handler. As with TagSupport, subclasses should
* not provide other constructors and are expected to call the
* superclass constructor.
*/
public OutSupport() {
super();
init();
}
// resets local state
private void init() {
value = def = null;
escapeXml = true;
needBody = false;
}
// Releases any resources we may have (or inherit)
public void release() {
super.release();
init();
}
//*********************************************************************
// Tag logic
// evaluates 'value' and determines if the body should be evaluted
public int doStartTag() throws JspException {
needBody = false; // reset state related to 'default'
this.bodyContent = null; // clean-up body (just in case container is pooling tag handlers)
try {
// print value if available; otherwise, try 'default'
if (value != null) {
out(pageContext, escapeXml, value);
return SKIP_BODY;
} else {
// if we don't have a 'default' attribute, just go to the body
if (def == null) {
needBody = true;
return EVAL_BODY_BUFFERED;
}
// if we do have 'default', print it
if (def != null) {
// good 'default'
out(pageContext, escapeXml, def);
}
return SKIP_BODY;
}
} catch (IOException ex) {
throw new JspException(ex.toString(), ex);
}
}
// prints the body if necessary; reports errors
public int doEndTag() throws JspException {
try {
if (!needBody)
return EVAL_PAGE; // nothing more to do
// trim and print out the body
if (bodyContent != null && bodyContent.getString() != null)
out(pageContext, escapeXml, bodyContent.getString().trim());
return EVAL_PAGE;
} catch (IOException ex) {
throw new JspException(ex.toString(), ex);
}
}
//*********************************************************************
// Public utility methods
/**
* Outputs <tt>text</tt> to <tt>pageContext</tt>'s current JspWriter.
* If <tt>escapeXml</tt> is true, performs the following substring
* replacements (to facilitate output to XML/HTML pages):
*
* & -> &
* < -> <
* > -> >
* " -> "
* ' -> '
*
* See also Util.escapeXml().
*/
public static void out(PageContext pageContext,
boolean escapeXml,
Object obj) throws IOException {
JspWriter w = pageContext.getOut();
if (!escapeXml) {
// write chars as is
if (obj instanceof Reader) {
Reader reader = (Reader)obj;
char[] buf = new char[4096];
int count;
while ((count=reader.read(buf, 0, 4096)) != -1) {
w.write(buf, 0, count);
}
} else {
w.write(obj.toString());
}
} else {
// escape XML chars
if (obj instanceof Reader) {
Reader reader = (Reader)obj;
char[] buf = new char[4096];
int count;
while ((count = reader.read(buf, 0, 4096)) != -1) {
writeEscapedXml(buf, count, w);
}
} else {
String text = obj.toString();
writeEscapedXml(text.toCharArray(), text.length(), w);
}
}
}
/**
*
* Optimized to create no extra objects and write directly
* to the JspWriter using blocks of escaped and unescaped characters
*
*/
private static void writeEscapedXml(char[] buffer, int length, JspWriter w) throws IOException{
int start = 0;
for (int i = 0; i < length; i++) {
char c = buffer[i];
if (c <= Util.HIGHEST_SPECIAL) {
char[] escaped = Util.specialCharactersRepresentation[c];
if (escaped != null) {
// add unescaped portion
if (start < i) {
w.write(buffer,start,i-start);
}
// add escaped xml
w.write(escaped);
start = i + 1;
}
}
}
// add rest of unescaped portion
if (start < length) {
w.write(buffer,start,length-start);
}
}
}
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