/* 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.camunda.bpm.engine.impl.scripting.engine;
import java.io.IOException;
import java.io.Reader;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import javax.script.AbstractScriptEngine;
import javax.script.Bindings;
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.camunda.bpm.engine.ProcessEngineException;
import org.camunda.bpm.engine.impl.el.ExpressionFactoryResolver;
import org.camunda.bpm.engine.impl.javax.el.ArrayELResolver;
import org.camunda.bpm.engine.impl.javax.el.BeanELResolver;
import org.camunda.bpm.engine.impl.javax.el.CompositeELResolver;
import org.camunda.bpm.engine.impl.javax.el.ELContext;
import org.camunda.bpm.engine.impl.javax.el.ELException;
import org.camunda.bpm.engine.impl.javax.el.ELResolver;
import org.camunda.bpm.engine.impl.javax.el.ExpressionFactory;
import org.camunda.bpm.engine.impl.javax.el.FunctionMapper;
import org.camunda.bpm.engine.impl.javax.el.ListELResolver;
import org.camunda.bpm.engine.impl.javax.el.MapELResolver;
import org.camunda.bpm.engine.impl.javax.el.ResourceBundleELResolver;
import org.camunda.bpm.engine.impl.javax.el.ValueExpression;
import org.camunda.bpm.engine.impl.javax.el.VariableMapper;
import org.camunda.bpm.engine.impl.juel.SimpleResolver;
import org.camunda.bpm.engine.impl.util.ReflectUtil;
/**
* ScriptEngine that used JUEL for script evaluation and compilation (JSR-223).
*
* Uses EL 1.1 if available, to resolve expressions. Otherwise it reverts to EL
* 1.0, using {@link ExpressionFactoryResolver}.
*
* @author Frederik Heremans
*/
public class JuelScriptEngine extends AbstractScriptEngine {
private ScriptEngineFactory scriptEngineFactory;
private ExpressionFactory expressionFactory;
public JuelScriptEngine(ScriptEngineFactory scriptEngineFactory) {
this.scriptEngineFactory = scriptEngineFactory;
// Resolve the ExpressionFactory
expressionFactory = ExpressionFactoryResolver.resolveExpressionFactory();
}
public JuelScriptEngine() {
this(null);
}
public Object eval(String script, ScriptContext scriptContext) throws ScriptException {
ValueExpression expr = parse(script, scriptContext);
return evaluateExpression(expr, scriptContext);
}
public Object eval(Reader reader, ScriptContext scriptContext) throws ScriptException {
return eval(readFully(reader), scriptContext);
}
public ScriptEngineFactory getFactory() {
synchronized (this) {
if (scriptEngineFactory == null) {
scriptEngineFactory = new JuelScriptEngineFactory();
}
}
return scriptEngineFactory;
}
public Bindings createBindings() {
return new SimpleBindings();
}
private Object evaluateExpression(ValueExpression expr, ScriptContext ctx) throws ScriptException {
try {
return expr.getValue(createElContext(ctx));
} catch (ELException elexp) {
throw new ScriptException(elexp);
}
}
private ELResolver createElResolver() {
CompositeELResolver compositeResolver = new CompositeELResolver();
compositeResolver.add(new ArrayELResolver());
compositeResolver.add(new ListELResolver());
compositeResolver.add(new MapELResolver());
compositeResolver.add(new ResourceBundleELResolver());
compositeResolver.add(new BeanELResolver());
return new SimpleResolver(compositeResolver);
}
private String readFully(Reader reader) throws ScriptException {
char[] array = new char[8192];
StringBuilder strBuffer = new StringBuilder();
int count;
try {
while ((count = reader.read(array, 0, array.length)) > 0) {
strBuffer.append(array, 0, count);
}
} catch (IOException exp) {
throw new ScriptException(exp);
}
return strBuffer.toString();
}
private ValueExpression parse(String script, ScriptContext scriptContext) throws ScriptException {
try {
return expressionFactory.createValueExpression(createElContext(scriptContext), script, Object.class);
} catch (ELException ele) {
throw new ScriptException(ele);
}
}
private ELContext createElContext(final ScriptContext scriptCtx) {
// Check if the ELContext is already stored on the ScriptContext
Object existingELCtx = scriptCtx.getAttribute("elcontext");
if (existingELCtx instanceof ELContext) {
return (ELContext) existingELCtx;
}
scriptCtx.setAttribute("context", scriptCtx, ScriptContext.ENGINE_SCOPE);
// Built-in function are added to ScriptCtx
scriptCtx.setAttribute("out:print", getPrintMethod(), ScriptContext.ENGINE_SCOPE);
SecurityManager securityManager = System.getSecurityManager();
if (securityManager == null) {
scriptCtx.setAttribute("lang:import", getImportMethod(), ScriptContext.ENGINE_SCOPE);
}
ELContext elContext = new ELContext() {
ELResolver resolver = createElResolver();
VariableMapper varMapper = new ScriptContextVariableMapper(scriptCtx);
FunctionMapper funcMapper = new ScriptContextFunctionMapper(scriptCtx);
@Override
public ELResolver getELResolver() {
return resolver;
}
@Override
public VariableMapper getVariableMapper() {
return varMapper;
}
@Override
public FunctionMapper getFunctionMapper() {
return funcMapper;
}
};
// Store the elcontext in the scriptContext to be able to reuse
scriptCtx.setAttribute("elcontext", elContext, ScriptContext.ENGINE_SCOPE);
return elContext;
}
private static Method getPrintMethod() {
try {
return JuelScriptEngine.class.getMethod("print", new Class[] { Object.class });
} catch (Exception exp) {
// Will never occur
return null;
}
}
public static void print(Object object) {
System.out.print(object);
}
private static Method getImportMethod() {
try {
return JuelScriptEngine.class.getMethod("importFunctions", new Class[] { ScriptContext.class, String.class, Object.class });
} catch (Exception exp) {
// Will never occur
return null;
}
}
public static void importFunctions(ScriptContext ctx, String namespace, Object obj) {
Class< ? > clazz = null;
if (obj instanceof Class) {
clazz = (Class< ? >) obj;
} else if (obj instanceof String) {
try {
clazz = ReflectUtil.loadClass((String) obj);
} catch (ProcessEngineException ae) {
throw new ELException(ae);
}
} else {
throw new ELException("Class or class name is missing");
}
Method[] methods = clazz.getMethods();
for (Method m : methods) {
int mod = m.getModifiers();
if (Modifier.isStatic(mod) && Modifier.isPublic(mod)) {
String name = namespace + ":" + m.getName();
ctx.setAttribute(name, m, ScriptContext.ENGINE_SCOPE);
}
}
}
/**
* Class representing a compiled script using JUEL.
*
* @author Frederik Heremans
*/
private class JuelCompiledScript extends CompiledScript {
private ValueExpression valueExpression;
JuelCompiledScript(ValueExpression valueExpression) {
this.valueExpression = valueExpression;
}
public ScriptEngine getEngine() {
// Return outer class instance
return JuelScriptEngine.this;
}
public Object eval(ScriptContext ctx) throws ScriptException {
return evaluateExpression(valueExpression, ctx);
}
}
/**
* ValueMapper that uses the ScriptContext to get variable values or value
* expressions.
*
* @author Frederik Heremans
*/
private class ScriptContextVariableMapper extends VariableMapper {
private ScriptContext scriptContext;
ScriptContextVariableMapper(ScriptContext scriptCtx) {
this.scriptContext = scriptCtx;
}
@Override
public ValueExpression resolveVariable(String variableName) {
int scope = scriptContext.getAttributesScope(variableName);
if (scope != -1) {
Object value = scriptContext.getAttribute(variableName, scope);
if (value instanceof ValueExpression) {
// Just return the existing ValueExpression
return (ValueExpression) value;
} else {
// Create a new ValueExpression based on the variable value
return expressionFactory.createValueExpression(value, Object.class);
}
}
return null;
}
@Override
public ValueExpression setVariable(String name, ValueExpression value) {
ValueExpression previousValue = resolveVariable(name);
scriptContext.setAttribute(name, value, ScriptContext.ENGINE_SCOPE);
return previousValue;
}
}
/**
* FunctionMapper that uses the ScriptContext to resolve functions in EL.
*
* @author Frederik Heremans
*/
private class ScriptContextFunctionMapper extends FunctionMapper {
private ScriptContext scriptContext;
ScriptContextFunctionMapper(ScriptContext ctx) {
this.scriptContext = ctx;
}
private String getFullFunctionName(String prefix, String localName) {
return prefix + ":" + localName;
}
@Override
public Method resolveFunction(String prefix, String localName) {
String functionName = getFullFunctionName(prefix, localName);
int scope = scriptContext.getAttributesScope(functionName);
if (scope != -1) {
// Methods are added as variables in the ScriptScope
Object attributeValue = scriptContext.getAttribute(functionName);
return (attributeValue instanceof Method) ? (Method) attributeValue : null;
} else {
return null;
}
}
}
}