io.github.microcks.util.el.TemplateEngine Maven / Gradle / Ivy
/*
* Copyright The Microcks Authors.
*
* 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 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();
}
}