io.github.microcks.util.el.TemplateEngine Maven / Gradle / Ivy
/*
* Licensed to Laurent Broudoux (the "Author") under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. Author 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 io.github.microcks.util.el;
/**
* An engine that can evaluate String templates holding some Expression Language {@code Expression}.
* Engine can be customized setting new expression delimiters (prefix and suffix). It embeds an
* {@code EvaluationContext} that can also be customized with variables and function registration before
* template evaluation using the {@code getValue()} method.
* @author laurent
*/
public class TemplateEngine {
public static final String DEFAULT_EXPRESSION_PREFIX = "{{";
public static final String DEFAULT_EXPRESSION_SUFFIX = "}}";
private String expressionPrefix = DEFAULT_EXPRESSION_PREFIX;
private String expressionSuffix = DEFAULT_EXPRESSION_SUFFIX;
private EvaluationContext context = new EvaluationContext();
protected TemplateEngine() {}
public String getExpressionPrefix() {
return expressionPrefix;
}
public void setExpressionPrefix(String expressionPrefix) {
this.expressionPrefix = expressionPrefix;
}
public String getExpressionSuffix() {
return expressionSuffix;
}
public void setExpressionSuffix(String expressionSuffix) {
this.expressionSuffix = expressionSuffix;
}
public EvaluationContext getContext() {
return context;
}
/**
* Evaluate the given string template, finding expressions within and evaluating them.
* @param template The string template to render.
* @return The rendered value of string template.
*/
public String getValue(String template) {
StringBuilder builder = new StringBuilder();
// Just delegate parsing stuffs to Expression parser to retrieve all the expressions ordered.
Expression[] expressions = ExpressionParser.parseExpressions(template, context, expressionPrefix, expressionSuffix);
// Now just go through expressions and evaluate them.
for (Expression expression : expressions) {
builder.append(expression.getValue(context));
}
return builder.toString();
}
}