/*
* Copyright 2013 Red Hat, Inc. and/or its affiliates.
*
* 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 org.jbpm.process.core.transformation;
import java.io.IOException;
import java.io.InputStream;
import java.io.StringWriter;
import java.util.HashMap;
import java.util.Map;
import java.util.Properties;
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.SimpleScriptContext;
import org.kie.api.runtime.process.DataTransformer;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* Implementation of <code>DataTransformer</code> that is based on standard
* Java scripting capabilities (javax.script).
* By default it uses Rhino scripting engine for JavaScript evaluation. But supports
* all scripting engine that are compliant with JSR 223. It's just a matter of
* placing them on classpath so Java itself can discover it and then new instance
* of this class will be registered for that engine. <br/>
* Allows to pass custom properties to the engine via property file that should be
* placed on root of the classpath named 'FQCN of the script engine factory'.properties
* <br/>
* When reading the properties file transformer recognizes three types of data:
* <ul>
* <li>boolean - when value is either true or false string</li>
* <li>integer - when value is a number (matches \d+ regex)</li>
* <li>string - default type</li>
* </ul>
* return value of the expression is either:
* <ul>
* <li>value returned from scriptEngine.eval if not null</li>
* <li>result of the output produced by the script engine - will be used only when eval returns null</li>
* </ul>
*/
public class JavaScriptingDataTransformer implements DataTransformer {
private static final Logger logger = LoggerFactory.getLogger(JavaScriptingDataTransformer.class);
private ScriptEngineFactory factory;
private ScriptEngine scriptEngine;
private Map<String, Object> engineProperties = new HashMap<String, Object>();
public JavaScriptingDataTransformer(ScriptEngineFactory factory) {
this.factory = factory;
this.scriptEngine = this.factory.getScriptEngine();
registerAttributes();
}
@Override
public Object transform(Object expression, Map<String, Object> parameters) {
return evaluateExpression(expression, parameters);
}
@Override
public Object compile(String expression, Map<String, Object> parameters) {
if (scriptEngine instanceof Compilable) {
logger.debug("Compiling expression {} with engine {}", expression, scriptEngine);
try {
return ((Compilable) scriptEngine).compile(expression);
} catch (ScriptException e) {
throw new RuntimeException("Error when compiling script", e);
}
}
logger.debug("Compilation not supported on engine {}", scriptEngine);
return expression;
}
protected Object evaluateExpression(Object expression, Map<String, Object> parameters) {
try {
Object result = null;
StringWriter writer = new StringWriter();
ScriptContext context = new SimpleScriptContext();
for (Map.Entry<String, Object> property : engineProperties.entrySet()) {
context.setAttribute(property.getKey(), property.getValue(), ScriptContext.ENGINE_SCOPE);
}
Bindings bindings = context.getBindings(ScriptContext.ENGINE_SCOPE);
bindings.putAll(parameters);
context.setBindings(bindings, ScriptContext.ENGINE_SCOPE);
context.setWriter(writer);
if (expression instanceof CompiledScript) {
logger.debug("About to evaluate compiled expression {} with bindings {} on engine", expression, parameters, scriptEngine);
result = ((CompiledScript) expression).eval(context);
} else {
logger.debug("About to evaluate expression {} with bindings {} on engine", expression, parameters, scriptEngine);
result = scriptEngine.eval(expression.toString(), context);
}
if (result == null) {
result = writer.toString();
}
return result;
} catch (ScriptException e) {
throw new RuntimeException("Error when evaluating script", e);
}
}
protected void registerAttributes() {
try {
InputStream propsIn = this.getClass().getResourceAsStream("/"+this.factory.getClass().getName()+".properties");
if (propsIn != null) {
Properties props = new Properties();
props.load(propsIn);
for (String propertyName : props.stringPropertyNames()) {
Object objectValue = resolveValue(props.getProperty(propertyName));
if (objectValue != null) {
engineProperties.put(propertyName, objectValue);
}
}
}
} catch (IOException e) {
logger.error("Error while loading script engine properties", e);
}
}
private Object resolveValue(String value) {
if (value == null) {
return null;
}
if (value.toLowerCase().matches("true|false")) {
return Boolean.parseBoolean(value);
} else if (value.matches("\\d+")) {
return Integer.parseInt(value);
}
return value;
}
}