com.google.gwt.dom.builder.shared.ElementBuilderImpl Maven / Gradle / Ivy
/*
* Copyright 2011 Google Inc.
*
* Licensed 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 com.google.gwt.dom.builder.shared;
import com.google.gwt.core.shared.GWT;
import com.google.gwt.dom.client.Element;
import com.google.gwt.regexp.shared.RegExp;
import com.google.gwt.safehtml.shared.SafeHtml;
/**
* Base implementation of {@link ElementBuilderBase} that handles state, but
* nothing else.
*
*
* DO NOT USE THIS CLASS. This class is an implementation class and may change
* in the future.
*
*
* This class is used to ensure that the HTML and DOM implementations throw the
* same exceptions, even if something is valid in one and not the other. For
* example, the DOM implementation supports changing an attribute after setting
* inner HTML, but the HTML version does not, so they should both throw an
* error. Otherwise, they would not be swappable.
*/
public abstract class ElementBuilderImpl {
/**
* A node in the builder stack.
*/
private static class StackNode {
private final ElementBuilderBase builder;
private StackNode next;
private final String tagName;
public StackNode(String tagName, ElementBuilderBase builder) {
this.builder = builder;
this.tagName = tagName;
}
}
/**
* A stack that allows quick access to its top element.
*
*
* FastPeekStack is implemented using a simple linked list of nodes to avoid
* the dynamic casts associated with the emulated version of
* {@link java.util.ArrayList}. When constructing a large DOM structure, such
* as a table, the dynamic casts in ArrayList can significantly degrade
* performance.
*
*/
private class FastPeekStack {
private static final String EMPTY_STACK_MESSAGE = "There are no elements on the stack.";
/**
* The top item in the stack.
*/
private StackNode top;
private int size = 0;
public boolean isEmpty() {
return (top == null);
}
public StackNode peek() {
assertNotEmpty();
return top;
}
/**
* Pop the current {@link StackNode} and return it.
*
*
* The popped node will be recycled and should not be saved.
*
*
* @return the popped node
*/
public StackNode pop() {
assertNotEmpty();
StackNode toRet = top;
top = top.next;
size--;
return toRet;
}
public void push(ElementBuilderBase builder, String tagName) {
StackNode node = new StackNode(tagName, builder);
node.next = top;
top = node;
size++;
}
public int size() {
return size;
}
/**
* Assert that the stack is not empty.
*
* @throws IllegalStateException if empty
*/
private void assertNotEmpty() {
if (isEmpty()) {
throw new IllegalStateException(EMPTY_STACK_MESSAGE);
}
}
}
/**
* A regex for matching valid HTML tags.
*/
private static RegExp HTML_TAG_REGEX;
private boolean asElementCalled;
/**
* True if the top most element has not yet been added.
*/
private boolean isEmpty = true;
/**
* True if HTML of text has been added.
*/
private boolean isHtmlOrTextAdded;
/**
* True if the start tag is still open (open bracket '<' but no close
* bracket '>').
*/
private boolean isStartTagOpen;
/**
* True if the style attribute has been opened and closed.
*/
private boolean isStyleClosed;
/**
* True if the style attribute is open.
*/
private boolean isStyleOpen;
/**
* The stack of element builders.
*/
private final FastPeekStack stack = new FastPeekStack();
public ElementBuilderImpl() {
if (HTML_TAG_REGEX == null) {
// Starts with a-z, plus 0 or more alphanumeric values (case insensitive).
HTML_TAG_REGEX = RegExp.compile("^[a-z][a-z0-9]*$", "i");
}
}
public void end() {
endImpl(getCurrentTagName());
}
public void end(String tagName) {
// Verify the tag name matches the expected tag.
String topItem = getCurrentTagName();
if (!topItem.equalsIgnoreCase(tagName)) {
throw new IllegalStateException("Specified tag \"" + tagName
+ "\" does not match the current element \"" + topItem + "\"");
}
// End the element.
endImpl(topItem);
}
public void endStyle() {
if (!isStyleOpen) {
throw new IllegalStateException(
"Attempting to close a style attribute, but the style attribute isn't open");
}
maybeCloseStyleAttribute();
}
/**
* Return the built DOM as an {@link Element}.
*
* @return the {@link Element} that was built
*/
public Element finish() {
if (!GWT.isClient()) {
throw new RuntimeException("asElement() can only be called from GWT client code.");
}
if (asElementCalled) {
throw new IllegalStateException("asElement() can only be called once.");
}
asElementCalled = true;
// End all open tags.
endAllTags();
return doFinishImpl();
}
public int getDepth() {
return stack.size();
}
public void html(SafeHtml html) {
assertStartTagOpen("html cannot be set on an element that already "
+ "contains other content or elements.");
lockCurrentElement();
doHtmlImpl(html);
}
public void onStart(String tagName, ElementBuilderBase builder) {
if (isEmpty) {
isEmpty = false;
} else if (stack.isEmpty()) {
// Check that we aren't creating another top level element.
throw new IllegalStateException("You can only build one top level element.");
} else {
// Check that the element supports children.
assertEndTagNotForbidden("child elements");
if (!getCurrentBuilder().isChildElementSupported()) {
throw new UnsupportedOperationException(getCurrentTagName()
+ " does not support child elements.");
}
}
// Check that asElement hasn't already been called.
if (isHtmlOrTextAdded) {
throw new IllegalStateException("Cannot append an element after setting text of html.");
}
// Validate the tagName.
assertValidTagName(tagName);
maybeCloseStartTag();
stack.push(builder, tagName);
isStartTagOpen = true;
isStyleOpen = false;
isStyleClosed = false;
isHtmlOrTextAdded = false;
}
/**
* Get the {@link StylesBuilder} used to add style properties to the current
* element.
*
* @return a {@link StylesBuilder}
*/
public abstract StylesBuilder style();
public void text(String text) {
assertStartTagOpen("text cannot be set on an element that already "
+ "contains other content or elements.");
lockCurrentElement();
doTextImpl(text);
}
/**
* Assert that the builder is in a state where an attribute can be added.
*
* @throw {@link IllegalStateException} if the start tag is closed
*/
protected void assertCanAddAttributeImpl() {
assertStartTagOpen("Attributes cannot be added after appending HTML or adding a child "
+ "element.");
maybeCloseStyleAttribute();
}
/**
* Assert that a style property can be added, and setup the state as if one is
* about to be added.
*/
protected void assertCanAddStylePropertyImpl() {
assertStartTagOpen("Style properties cannot be added after appending HTML or adding a child "
+ "element.");
// Check if a style attribute already exists.
if (isStyleClosed) {
throw new IllegalStateException(
"Style properties must be added at the same time. If you already added style properties,"
+ " you cannot add more after adding non-style attributes.");
}
// Open the style attribute.
if (!isStyleOpen) {
isStyleOpen = true;
doOpenStyleImpl();
}
}
/**
* Assert that the specified tag name is valid.
*
* @throws IllegalArgumentException if not valid
*/
protected void assertValidTagName(String tagName) {
if (!HTML_TAG_REGEX.test(tagName)) {
throw new IllegalArgumentException("The specified tag name is invalid: " + tagName);
}
}
/**
* Close the start tag.
*/
protected abstract void doCloseStartTagImpl();
/**
* Close the style attribute.
*/
protected abstract void doCloseStyleAttributeImpl();
/**
* Self-close the start tag. This method is called for elements that forbid
* the end tag.
*/
protected abstract void doEndStartTagImpl();
/**
* End the specified tag.
*
* @param tagName the name of the tag to end
*/
protected abstract void doEndTagImpl(String tagName);
/**
* Return the build element.
*
* @return the element
*/
protected abstract Element doFinishImpl();
/**
* Set the specified html as the inner HTML of the current element.
*
* @param html the HTML to set
*/
protected abstract void doHtmlImpl(SafeHtml html);
/**
* Open the style attribute.
*/
protected abstract void doOpenStyleImpl();
/**
* Set the specified text as the inner text of the current element.
*
* @param text the text to set
*/
protected abstract void doTextImpl(String text);
/**
* End all open tags, including the root element.
*
*
* Doing so also ensures that all builder methods will throw an exception
* because the stack is empty, and a new element cannot be started.
*
*/
protected void endAllTags() {
while (!stack.isEmpty()) {
end();
}
}
/**
* Lock the current element, preventing any additional changes to it. The only
* valid option is to call {@link #end()}.
*/
protected void lockCurrentElement() {
maybeCloseStartTag();
assertEndTagNotForbidden("html");
isHtmlOrTextAdded = true;
}
/**
* Assert that the current builder does not forbid end tags.
*
* @param operation the operation that the user is attempting
* @throw {@link UnsupportedOperationException} if not supported
*/
private void assertEndTagNotForbidden(String operation) {
if (getCurrentBuilder().isEndTagForbidden()) {
throw new UnsupportedOperationException(getCurrentTagName() + " does not support "
+ operation);
}
}
/**
* Assert that the start tag is still open.
*
* @param message the error message if the start tag is not open
* @throw {@link IllegalStateException} if the start tag is closed
*/
private void assertStartTagOpen(String message) {
if (!isStartTagOpen) {
throw new IllegalStateException(message);
}
}
/**
* End the current element without checking the tag name.
*
* @param tagName the tag name to end
*/
private void endImpl(String tagName) {
// Close the start tag.
maybeCloseStartTag();
/*
* End the tag. The tag name is safe because it comes from the stack, and
* tag names are checked before they are added to the stack.
*/
if (getCurrentBuilder().isEndTagForbidden()) {
doEndStartTagImpl();
} else {
doEndTagImpl(tagName);
}
// Popup the item off the top of the stack.
isStartTagOpen = false; // Closed because this element was added.
isStyleClosed = true; // Too late to add styles.
stack.pop();
/*
* If this element was added, then we did not add html or text to the
* parent.
*/
isHtmlOrTextAdded = false;
}
/**
* Get the builder at the top of the stack.
*
* @return an {@link ElementBuilderBase}
* @throws IllegalStateException if there are no elements on the stack
*/
private ElementBuilderBase getCurrentBuilder() {
return stack.peek().builder;
}
/**
* Get the tag name of the element at the top of the stack.
*
* @return a tag name
* @throws IllegalStateException if there are no elements on the stack
*/
private String getCurrentTagName() {
return stack.peek().tagName;
}
/**
* Close the start tag if it is still open.
*/
private void maybeCloseStartTag() {
maybeCloseStyleAttribute();
if (isStartTagOpen) {
isStartTagOpen = false;
/*
* Close the start tag, unless the end tag is forbidden. If the end tag is
* forbidden, the only valid call is to #end(), which will self end the
* start tag.
*/
if (!getCurrentBuilder().isEndTagForbidden()) {
doCloseStartTagImpl();
}
}
}
/**
* Close the style attribute if it is still open.
*/
private void maybeCloseStyleAttribute() {
if (isStyleOpen) {
isStyleOpen = false;
isStyleClosed = true;
doCloseStyleAttributeImpl();
}
}
}