com.google.gwt.codegen.server.StringGenerator 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.codegen.server;
/**
* Helper class to produce string expressions consisting of literals and
* computed values.
*/
public abstract class StringGenerator {
/**
* Type of expression being processed.
*/
protected enum Type {
LITERAL,
PRIMITIVE,
SAFE,
OTHER,
}
/**
* Create a {@link StringGenerator} instance.
*
* @param buf
* @param returnsSafeHtml
* @return {@link StringGenerator} instance
*/
public static StringGenerator create(StringBuilder buf, boolean returnsSafeHtml) {
if (returnsSafeHtml) {
return new SafeHtmlStringGenerator(buf);
} else {
return new PlainStringGenerator(buf);
}
}
/**
* Output string buffer.
*/
protected final StringBuilder buf;
/**
* True if we are in the middle of a string literal.
*/
protected boolean inString;
/**
* Initialize the StringGenerator with an output buffer.
*
* @param buf output buffer
*/
protected StringGenerator(StringBuilder buf) {
this.buf = buf;
inString = false;
}
/**
* Append an expression to this string expression.
*
* @param expression to add
* @param isSafeHtmlTyped true if the expression is known to be of type
* {@link com.google.gwt.safehtml.shared.SafeHtml SafeHtml}; only relevant
* if this generator has been initialized to generate a
* {@link com.google.gwt.safehtml.shared.SafeHtml SafeHtml}-valued
* expression
* @param isPrimitiveTyped true if the expression is of a primitive type;
* only relevant if this generator has been initialized to generate a
* {@link com.google.gwt.safehtml.shared.SafeHtml SafeHtml}-valued
* expression
* @param needsConversionToString true if the expression is not known to be
* of type String and needs to be converted
*/
public void appendExpression(String expression, boolean isSafeHtmlTyped,
boolean isPrimitiveTyped, boolean needsConversionToString) {
if (inString) {
buf.append('"');
afterExpression(Type.LITERAL);
inString = false;
}
Type type;
if (isPrimitiveTyped) {
type = Type.PRIMITIVE;
} else if (isSafeHtmlTyped) {
type = Type.SAFE;
} else {
type = Type.OTHER;
}
beforeExpression(type);
if (type == Type.OTHER && needsConversionToString) {
forceStringPrefix();
}
buf.append(expression);
if (type == Type.OTHER && needsConversionToString) {
forceStringSuffix();
}
afterExpression(type);
}
/**
* Append part of a string literal.
*
* @param str part of string literal
*/
public void appendStringLiteral(String str) {
if (!inString) {
beforeExpression(Type.LITERAL);
buf.append('"');
inString = true;
}
buf.append(str);
}
/**
* Append an expression to this string expression.
*
* @param expression to add, which the caller asserts is String-valued
*/
public void appendStringValuedExpression(String expression) {
appendExpression(expression, false, false, false);
}
/**
* Complete the string, closing an open quote and handling empty strings.
*/
public void completeString() {
if (inString) {
buf.append('"');
afterExpression(Type.LITERAL);
}
finishOutput();
}
protected abstract void afterExpression(Type type);
protected abstract void beforeExpression(Type type);
protected abstract void finishOutput();
protected abstract void forceStringPrefix();
protected abstract void forceStringSuffix();
}