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feilong is a suite of core and expanded libraries that include utility classes, http, excel,cvs, io classes, and much much more.
/*
* Copyright (C) 2008 feilong
*
* 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.feilong.spring.expression;
import static com.feilong.core.util.MapUtil.newConcurrentHashMap;
import java.util.Map;
import org.springframework.expression.EvaluationContext;
import org.springframework.expression.Expression;
import org.springframework.expression.ExpressionParser;
import org.springframework.expression.ParserContext;
import org.springframework.expression.spel.standard.SpelExpressionParser;
import org.springframework.expression.spel.support.StandardEvaluationContext;
import com.feilong.core.Validate;
/**
* Spring Expression Language 工具类.
*
*
* 同很多可用的Java 表达式语言相比，例如{@link OGNL}，{@link MVEL}和JBoss EL，SpEL的诞生是为了给Spring社区提供一个可以给Spring目录中所有产品提供单一良好支持的表达式语言。
*
*
* @author feilong
* @see Spring Expression
* Language (SpEL)
* @see commons-ognl
* @see mvel
* @since 3.0.2 move from feilong-spring project
*/
@SuppressWarnings("squid:S1192") //String literals should not be duplicated
public final class SpelUtil{
/** The expression parser. */
private static ExpressionParser expressionParser = new SpelExpressionParser();
/**
* expressionString和 {@link Expression} 简单的 cache.
*
* @since 4.0.6
*/
private static final Map EXPRESSION_STRING_AND_EXPRESSION_MAP = newConcurrentHashMap();
//---------------------------------------------------------------
/** Don't let anyone instantiate this class. */
private SpelUtil(){
//AssertionError不是必须的. 但它可以避免不小心在类的内部调用构造器. 保证该类在任何情况下都不会被实例化.
//see 《Effective Java》 2nd
throw new AssertionError("No " + getClass().getName() + " instances for you!");
}
//---------------------------------------------------------------
/**
* Gets the template value.
*
* @param
* the generic type
* @param expressionString
* the expression string
* @return the template value
* @see org.springframework.expression.ParserContext#TEMPLATE_EXPRESSION
* @see org.springframework.expression.common.TemplateParserContext
*/
@SuppressWarnings("unchecked")
public static T getTemplateValue(String expressionString){
Validate.notBlank(expressionString, "expressionString can't be blank!");
//---------------------------------------------------------------
Expression expression = load(expressionString, ParserContext.TEMPLATE_EXPRESSION);
return (T) expression.getValue();
}
/**
* Gets the value.
*
* 示例1:
*
*
*
*
*
* String ex = "'Hello,World'";
*
* assertEquals("Hello,World", SpelUtil.getValue(ex));
* assertEquals(11, SpelUtil.getValue(ex + ".length()"));
* assertEquals("Hello,World!", SpelUtil.getValue(ex + ".concat('!')"));
* assertEquals(String.class, SpelUtil.getValue(ex + ".class"));
* assertEquals(11, SpelUtil.getValue(ex + ".bytes.length"));
* assertEquals("HELLO,WORLD", SpelUtil.getValue("new String(" + ex + ").toUpperCase()"));
*
*
*
*
*
* 示例2:
*
*
*
*
*
* String expressionString = "T(com.feilong.core.lang.StringUtil).tokenizeToStringArray('xin,jin',',')";
*
* String[] values = SpelUtil.getValue(expressionString);
* assertThat(toList(values), allOf(hasItem("xin"), hasItem("jin")));
*
*
*
*
*
* @param
* the generic type
* @param expressionString
* the expression string
* @return 如果 expressionString 是null,抛出 {@link NullPointerException}
* 如果 expressionString 是blank,抛出 {@link IllegalArgumentException}
*
* @see org.springframework.expression.Expression#getValue()
*/
@SuppressWarnings("unchecked")
public static T getValue(String expressionString){
Validate.notBlank(expressionString, "expressionString can't be blank!");
//---------------------------------------------------------------
Expression expression = load(expressionString, null);
return (T) expression.getValue();
}
//---------------------------------------------------------------
/**
* Gets the value.
*
* @param
* the value type
* @param
* the generic type
* @param expressionString
* the expression string
* @param rootObject
* the root object to use, see
* {@link org.springframework.expression.spel.support.StandardEvaluationContext#StandardEvaluationContext(Object)
* StandardEvaluationContext}
* @return 如果 expressionString 是null,抛出 {@link NullPointerException}
* 如果 expressionString 是blank,抛出 {@link IllegalArgumentException}
* 如果 rootObject 是null或者empty,返回 {@link #getValue(String)}
* @see org.springframework.expression.Expression#getValue(EvaluationContext)
* @see StandardEvaluationContext
* @see org.springframework.expression.spel.support.SimpleEvaluationContext
* @since 4.0.6
*/
@SuppressWarnings("unchecked")
public static V getValue(String expressionString,T rootObject){
Validate.notBlank(expressionString, "expressionString can't be blank!");
//---------------------------------------------------------------
if (null == rootObject){
return getValue(expressionString);
}
//---------------------------------------------------------------
EvaluationContext evaluationContext = new StandardEvaluationContext(rootObject);
Expression expression = load(expressionString, null);
return (V) expression.getValue(evaluationContext);
}
//---------------------------------------------------------------
/**
* Load.
*
* @param expressionString
* the expression string
* @param context
* the context
* @return the expression
* @since 4.1.2
*/
private static Expression load(String expressionString,ParserContext context){
Expression expression = EXPRESSION_STRING_AND_EXPRESSION_MAP.get(expressionString);
if (null != expression){
return expression;
}
//---------------------------------------------------------------
expression = expressionParser.parseExpression(expressionString, context);
EXPRESSION_STRING_AND_EXPRESSION_MAP.put(expressionString, expression);
return expression;
}
}