org.springframework.scripting.bsh.BshScriptUtils Maven / Gradle / Ivy
/*
* Copyright 2002-2023 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
*
* https://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.springframework.scripting.bsh;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import bsh.EvalError;
import bsh.Interpreter;
import bsh.Primitive;
import bsh.XThis;
import org.springframework.core.NestedRuntimeException;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.util.ClassUtils;
import org.springframework.util.ObjectUtils;
import org.springframework.util.ReflectionUtils;
/**
* Utility methods for handling BeanShell-scripted objects.
*
* @author Rob Harrop
* @author Juergen Hoeller
* @since 2.0
*/
public abstract class BshScriptUtils {
/**
* Create a new BeanShell-scripted object from the given script source.
* With this {@code createBshObject} variant, the script needs to
* declare a full class or return an actual instance of the scripted object.
* @param scriptSource the script source text
* @return the scripted Java object
* @throws EvalError in case of BeanShell parsing failure
*/
public static Object createBshObject(String scriptSource) throws EvalError {
return createBshObject(scriptSource, null, null);
}
/**
* Create a new BeanShell-scripted object from the given script source,
* using the default ClassLoader.
*
The script may either be a simple script that needs a corresponding proxy
* generated (implementing the specified interfaces), or declare a full class
* or return an actual instance of the scripted object (in which case the
* specified interfaces, if any, need to be implemented by that class/instance).
* @param scriptSource the script source text
* @param scriptInterfaces the interfaces that the scripted Java object is
* supposed to implement (may be {@code null} or empty if the script itself
* declares a full class or returns an actual instance of the scripted object)
* @return the scripted Java object
* @throws EvalError in case of BeanShell parsing failure
* @see #createBshObject(String, Class[], ClassLoader)
*/
public static Object createBshObject(String scriptSource, @Nullable Class... scriptInterfaces) throws EvalError {
return createBshObject(scriptSource, scriptInterfaces, ClassUtils.getDefaultClassLoader());
}
/**
* Create a new BeanShell-scripted object from the given script source.
*
The script may either be a simple script that needs a corresponding proxy
* generated (implementing the specified interfaces), or declare a full class
* or return an actual instance of the scripted object (in which case the
* specified interfaces, if any, need to be implemented by that class/instance).
* @param scriptSource the script source text
* @param scriptInterfaces the interfaces that the scripted Java object is
* supposed to implement (may be {@code null} or empty if the script itself
* declares a full class or returns an actual instance of the scripted object)
* @param classLoader the ClassLoader to use for evaluating the script
* @return the scripted Java object
* @throws EvalError in case of BeanShell parsing failure
*/
public static Object createBshObject(String scriptSource, @Nullable Class[] scriptInterfaces, @Nullable ClassLoader classLoader)
throws EvalError {
Object result = evaluateBshScript(scriptSource, scriptInterfaces, classLoader);
if (result instanceof Class clazz) {
try {
return ReflectionUtils.accessibleConstructor(clazz).newInstance();
}
catch (Throwable ex) {
throw new IllegalStateException("Could not instantiate script class: " + clazz.getName(), ex);
}
}
else {
return result;
}
}
/**
* Evaluate the specified BeanShell script based on the given script source,
* returning the Class defined by the script.
*
The script may either declare a full class or return an actual instance of
* the scripted object (in which case the Class of the object will be returned).
* In any other case, the returned Class will be {@code null}.
* @param scriptSource the script source text
* @param classLoader the ClassLoader to use for evaluating the script
* @return the scripted Java class, or {@code null} if none could be determined
* @throws EvalError in case of BeanShell parsing failure
*/
@Nullable
static Class determineBshObjectType(String scriptSource, @Nullable ClassLoader classLoader) throws EvalError {
Assert.hasText(scriptSource, "Script source must not be empty");
Interpreter interpreter = new Interpreter();
if (classLoader != null) {
interpreter.setClassLoader(classLoader);
}
Object result = interpreter.eval(scriptSource);
if (result instanceof Class clazz) {
return clazz;
}
else if (result != null) {
return result.getClass();
}
else {
return null;
}
}
/**
* Evaluate the specified BeanShell script based on the given script source,
* keeping a returned script Class or script Object as-is.
*
The script may either be a simple script that needs a corresponding proxy
* generated (implementing the specified interfaces), or declare a full class
* or return an actual instance of the scripted object (in which case the
* specified interfaces, if any, need to be implemented by that class/instance).
* @param scriptSource the script source text
* @param scriptInterfaces the interfaces that the scripted Java object is
* supposed to implement (may be {@code null} or empty if the script itself
* declares a full class or returns an actual instance of the scripted object)
* @param classLoader the ClassLoader to use for evaluating the script
* @return the scripted Java class or Java object
* @throws EvalError in case of BeanShell parsing failure
*/
static Object evaluateBshScript(
String scriptSource, @Nullable Class[] scriptInterfaces, @Nullable ClassLoader classLoader)
throws EvalError {
Assert.hasText(scriptSource, "Script source must not be empty");
Interpreter interpreter = new Interpreter();
interpreter.setClassLoader(classLoader);
Object result = interpreter.eval(scriptSource);
if (result != null) {
return result;
}
else {
// Simple BeanShell script: Let's create a proxy for it, implementing the given interfaces.
if (ObjectUtils.isEmpty(scriptInterfaces)) {
throw new IllegalArgumentException("Given script requires a script proxy: " +
"At least one script interface is required.\nScript: " + scriptSource);
}
XThis xt = (XThis) interpreter.eval("return this");
return Proxy.newProxyInstance(classLoader, scriptInterfaces, new BshObjectInvocationHandler(xt));
}
}
/**
* InvocationHandler that invokes a BeanShell script method.
*/
private static class BshObjectInvocationHandler implements InvocationHandler {
private final XThis xt;
public BshObjectInvocationHandler(XThis xt) {
this.xt = xt;
}
@Override
@Nullable
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
if (ReflectionUtils.isEqualsMethod(method)) {
return (isProxyForSameBshObject(args[0]));
}
else if (ReflectionUtils.isHashCodeMethod(method)) {
return this.xt.hashCode();
}
else if (ReflectionUtils.isToStringMethod(method)) {
return "BeanShell object [" + this.xt + "]";
}
try {
Object result = this.xt.invokeMethod(method.getName(), args);
if (result == Primitive.NULL || result == Primitive.VOID) {
return null;
}
if (result instanceof Primitive primitive) {
return primitive.getValue();
}
return result;
}
catch (EvalError ex) {
throw new BshExecutionException(ex);
}
}
private boolean isProxyForSameBshObject(Object obj) {
if (!Proxy.isProxyClass(obj.getClass())) {
return false;
}
InvocationHandler ih = Proxy.getInvocationHandler(obj);
return (ih instanceof BshObjectInvocationHandler that && this.xt.equals(that.xt));
}
}
/**
* Exception to be thrown on script execution failure.
*/
@SuppressWarnings("serial")
public static final class BshExecutionException extends NestedRuntimeException {
private BshExecutionException(EvalError ex) {
super("BeanShell script execution failed", ex);
}
}
}