75 lines
2.0 KiB
Java
75 lines
2.0 KiB
Java
/**
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* Copyright (c) 2011-2019, James Zhan 詹波 (jfinal@126.com).
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.jfinal.kit;
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import java.util.Map;
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import com.jfinal.template.Directive;
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import com.jfinal.template.Engine;
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import com.jfinal.template.Env;
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import com.jfinal.template.Template;
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import com.jfinal.template.io.Writer;
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import com.jfinal.template.stat.Scope;
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/**
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* EL 表达式语言求值工具类
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*
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* <pre>
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* 1：不带参示例
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* Integer value = ElKit.eval("1 + 2 * 3");
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*
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* 2：带参示例
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* Kv data = Kv.by("a", 2).set("b", 3);
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* Integer value = ElKit.eval("1 + a * b", data);
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* </pre>
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*/
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public class ElKit {
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private static Engine engine = new Engine();
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private static final String RETURN_VALUE_KEY = "_RETURN_VALUE_";
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static {
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engine.addDirective("eval", InnerEvalDirective.class);
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}
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public static Engine getEngine() {
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return engine;
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}
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public static <T> T eval(String expr) {
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return eval(expr, Kv.create());
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}
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@SuppressWarnings("unchecked")
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public static <T> T eval(String expr, Map<?, ?> data) {
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String stringTemplate = "#eval(" + expr + ")";
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Template template = engine.getTemplateByString(stringTemplate);
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template.render(data, (java.io.Writer)null);
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return (T)data.get(RETURN_VALUE_KEY);
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}
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public static class InnerEvalDirective extends Directive {
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public void exec(Env env, Scope scope, Writer writer) {
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Object value = exprList.eval(scope);
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scope.set(RETURN_VALUE_KEY, value);
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}
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}
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}
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