com.google.gwt.uibinder.attributeparsers.FieldReferenceConverter Maven / Gradle / Ivy
/*
* Copyright 2009 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.uibinder.attributeparsers;
import com.google.gwt.core.ext.typeinfo.JType;
import com.google.gwt.uibinder.rebind.FieldManager;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
/**
* Deals with field references, e.g. the bits in braces here: <div
* class="{style.enabled} fancy {style.impressive}" />, by converting
* them to java expressions (with the help of a
* {@link FieldReferenceConverter.Delegate}).
*
* A field reference is one or more segments separated by dots. The first
* segment is considered to be a reference to a ui field, and succeeding
* segments are method calls. So, "{able.baker.charlie}" becomes
* "able.baker().charlie()".
*
* A field reference starts with '{' and is followed immediately by a character
* that can legally start a java identifier—that is a letter, $, or
* underscore. Braces not followed by such a character are left in place.
*
* For convenience when dealing with generated CssResources, field segments with
* dashes are converted to camel case. That is, {able.baker-charlie} is the same
* as {able.bakerCharlie}
*
* Opening braces may be escape by doubling them. That is, "{{foo}" will
* converted to "{foo}", with no field reference detected.
*/
public class FieldReferenceConverter {
/**
* May be thrown by the {@link FieldReferenceConverter.Delegate} for badly
* formatted input.
*/
@SuppressWarnings("serial")
public static class IllegalFieldReferenceException extends RuntimeException {
}
/**
* Responsible for the bits around and between the field references. May throw
* IllegalFieldReferenceException as it sees fit.
*/
interface Delegate {
/**
* Returns the type any parsed field references are expected to return.
*/
JType getType();
/**
* Called for fragment around and between field references.
*
* Note that it will be called with empty strings if these surrounding bits
* are empty. E.g., "{style.enabled} fancy {style.impressive}" would call
* this method three times, with "", " fancy ", and "".
*
* A string with no field references is treated as a single fragment, and
* causes a single call to this method.
*/
String handleFragment(String fragment)
throws IllegalFieldReferenceException;
/**
* Called for each expanded field reference, to allow it to be stitched
* together with surrounding fragments.
*/
String handleReference(String reference)
throws IllegalFieldReferenceException;
}
/**
* Used by {@link #hasFieldReferences}. Passthrough implementation that notes
* when handleReference has been called.
*/
private static final class Telltale implements
FieldReferenceConverter.Delegate {
boolean hasComputed = false;
public JType getType() {
return null;
}
public String handleFragment(String fragment) {
return fragment;
}
public String handleReference(String reference) {
hasComputed = true;
return reference;
}
public boolean hasComputed() {
return hasComputed;
}
}
private static final Pattern BRACES = Pattern.compile("[{]([^}]*)[}]");
private static final Pattern LEGAL_FIRST_CHAR = Pattern.compile("^[$_a-zA-Z].*");
/**
* Returns true if the given string holds one or more field references.
*/
public static boolean hasFieldReferences(String string) {
Telltale telltale = new Telltale();
new FieldReferenceConverter(null).convert(string, telltale);
return telltale.hasComputed();
}
private final CssNameConverter cssConverter = new CssNameConverter();
private final FieldManager fieldManager;
/**
* @param fieldManager to register parsed references with. May be null
*/
FieldReferenceConverter(FieldManager fieldManager) {
this.fieldManager = fieldManager;
}
/**
* @throws IllegalFieldReferenceException if the delegate does
*/
public String convert(String in, Delegate delegate) {
StringBuilder b = new StringBuilder();
int nextFindStart = 0;
int lastMatchEnd = 0;
Matcher m = BRACES.matcher(in);
while (m.find(nextFindStart)) {
String fieldReference = m.group(1);
if (!legalFirstCharacter(fieldReference)) {
nextFindStart = m.start() + 2;
continue;
}
String precedingFragment = in.substring(lastMatchEnd, m.start());
precedingFragment = handleFragment(precedingFragment, delegate);
b.append(precedingFragment);
if (fieldManager != null) {
fieldManager.registerFieldReference(fieldReference, delegate.getType());
}
fieldReference = expandDots(fieldReference);
b.append(delegate.handleReference(fieldReference));
nextFindStart = lastMatchEnd = m.end();
}
b.append(handleFragment(in.substring(lastMatchEnd), delegate));
return b.toString();
}
private String expandDots(String value) {
StringBuilder b = new StringBuilder();
String[] segments = value.split("[.]");
for (String segment : segments) {
segment = cssConverter.convertName(segment);
if (b.length() == 0) {
b.append(segment); // field name
} else {
b.append(".").append(segment).append("()");
}
}
return b.toString();
}
private String handleFragment(String fragment, Delegate delegate) {
fragment = fragment.replace("{{", "{");
return delegate.handleFragment(fragment);
}
private boolean legalFirstCharacter(String fieldReference) {
return LEGAL_FIRST_CHAR.matcher(fieldReference).matches();
}
}