/
SpelScriptEngine.java
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/
SpelScriptEngine.java
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/*
* Copyright 2010-2011 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
*
* 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.googlecode.starflow.core.script.spel;
import java.io.IOException;
import java.io.Reader;
import java.util.HashMap;
import java.util.Map;
import javax.script.AbstractScriptEngine;
import javax.script.Bindings;
import javax.script.Compilable;
import javax.script.CompiledScript;
import javax.script.ScriptContext;
import javax.script.ScriptEngine;
import javax.script.ScriptEngineFactory;
import javax.script.ScriptException;
import javax.script.SimpleBindings;
import org.springframework.expression.Expression;
import org.springframework.expression.ExpressionParser;
import org.springframework.expression.spel.standard.SpelExpressionParser;
import org.springframework.expression.spel.support.StandardEvaluationContext;
/**
*
* @author libinsong1204@gmail.com
* @date 2011-1-18 上午11:03:34
* @version
*/
public class SpelScriptEngine extends AbstractScriptEngine implements
Compilable {
public static final String ROOT_OBJECT = "root";
private volatile SpelScriptEngineFactory factory;
@Override
public Object eval(String script, ScriptContext context)
throws ScriptException {
Expression expression = parse(script);
return evalExpression(expression, context);
}
private Expression parse(String script) {
ExpressionParser expressionParser = getExpressionParser();
return expressionParser.parseExpression(script);
}
private Object evalExpression(Expression expression,
ScriptContext scriptContext) {
StandardEvaluationContext standardEvaluationContext = getStandardEvaluationContext(scriptContext);
return expression.getValue(standardEvaluationContext);
}
private StandardEvaluationContext getStandardEvaluationContext(
ScriptContext scriptContext) {
StandardEvaluationContext standardEvaluationContext = new StandardEvaluationContext(
scriptContext.getAttribute(ROOT_OBJECT));
standardEvaluationContext.setVariables(getVariables(scriptContext));
return standardEvaluationContext;
}
private Map<String, Object> getVariables(ScriptContext scriptContext) {
Map<String, Object> variables = new HashMap<String, Object>();
if (scriptContext.getBindings(ScriptContext.GLOBAL_SCOPE) != null) {
variables.putAll(scriptContext
.getBindings(ScriptContext.GLOBAL_SCOPE));
}
if (scriptContext.getBindings(ScriptContext.ENGINE_SCOPE) != null) {
variables.putAll(scriptContext
.getBindings(ScriptContext.ENGINE_SCOPE));
}
return variables;
}
private ExpressionParser getExpressionParser() {
return new SpelExpressionParser();
}
@Override
public Object eval(Reader reader, ScriptContext context)
throws ScriptException {
return eval(readFully(reader), context);
}
@Override
public Bindings createBindings() {
return new SimpleBindings();
}
@Override
public ScriptEngineFactory getFactory() {
if (factory == null) {
synchronized (this) {
if (factory == null) {
factory = new SpelScriptEngineFactory();
}
}
}
return factory;
}
private class SpelCompiledScript extends CompiledScript {
private final Expression expression;
public SpelCompiledScript(Expression expression) {
this.expression = expression;
}
@Override
public Object eval(ScriptContext context) throws ScriptException {
return evalExpression(expression, context);
}
@Override
public ScriptEngine getEngine() {
return SpelScriptEngine.this;
}
}
@Override
public CompiledScript compile(String script) throws ScriptException {
return new SpelCompiledScript(parse(script));
}
@Override
public CompiledScript compile(Reader script) throws ScriptException {
return compile(readFully(script));
}
private static final String readFully(Reader reader) throws ScriptException {
char[] arr = new char[8 * 1024];
StringBuilder buf = new StringBuilder();
int numChars;
try {
while ((numChars = reader.read(arr, 0, arr.length)) > 0) {
buf.append(arr, 0, numChars);
}
} catch (IOException exp) {
throw new ScriptException(exp);
}
return buf.toString();
}
}