com.livk.commons.expression.freemarker.FreeMarkerExpressionResolver Maven / Gradle / Ivy
/*
* Copyright 2021-2024 spring-boot-extension the original author or 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
*
* https://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.livk.commons.expression.freemarker;
import com.livk.commons.expression.CacheExpressionResolver;
import com.livk.commons.expression.Context;
import freemarker.template.Configuration;
import freemarker.template.Template;
import freemarker.template.TemplateException;
import lombok.RequiredArgsConstructor;
import java.io.IOException;
import java.io.StringWriter;
/**
* 使用FreeMarker实现的表达式解析器
*
* @author livk
*/
@RequiredArgsConstructor
public class FreeMarkerExpressionResolver extends CacheExpressionResolver {
private static final Configuration DEFAULT_CONFIG = new Configuration(
Configuration.DEFAULT_INCOMPATIBLE_IMPROVEMENTS);
private static final String TEMPLATE_NAME = "template";
private final Configuration configuration;
/**
* Instantiates a new Free marker expression resolver.
*/
public FreeMarkerExpressionResolver() {
this(DEFAULT_CONFIG);
}
@Override
protected Template compile(String value) throws IOException {
return new Template(TEMPLATE_NAME, value, configuration);
}
@Override
protected T calculate(Template template, Context context, Class returnType)
throws TemplateException, IOException {
if (returnType.isAssignableFrom(String.class)) {
StringWriter result = new StringWriter(1024);
template.process(context, result);
return returnType.cast(result.toString());
}
throw new UnsupportedOperationException("Classes other than String and its parent class are not supported");
}
}