net.shibboleth.utilities.java.support.scripting.EvaluableScript Maven / Gradle / Ivy
/*
* Licensed to the University Corporation for Advanced Internet Development,
* Inc. (UCAID) under one or more contributor license agreements. See the
* NOTICE file distributed with this work for additional information regarding
* copyright ownership. The UCAID licenses this file to You 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 net.shibboleth.utilities.java.support.scripting;
import java.io.File;
import java.io.IOException;
import java.nio.charset.Charset;
import javax.annotation.Nonnull;
import javax.annotation.Nullable;
import javax.script.Bindings;
import javax.script.Compilable;
import javax.script.CompiledScript;
import javax.script.ScriptContext;
import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;
import net.shibboleth.utilities.java.support.annotation.constraint.NotEmpty;
import net.shibboleth.utilities.java.support.logic.Constraint;
import net.shibboleth.utilities.java.support.primitive.StringSupport;
import com.google.common.io.Files;
/** This is a helper class that takes care of reading in, optionally compiling, and evaluating a script. */
public class EvaluableScript {
/** The scripting language. */
private final String scriptLanguage;
/** The script to execute. */
private final String script;
/** The script engine to execute the script. */
private ScriptEngine scriptEngine;
/** The compiled form of the script, if the script engine supports compiling. */
private CompiledScript compiledScript;
/**
* Constructor.
*
* @param engineName the JSR-223 scripting engine name
* @param scriptSource the script source
*
* @throws ScriptException thrown if the scripting engine supports compilation and the script does not compile
*/
public EvaluableScript(@Nonnull @NotEmpty String engineName, @Nonnull @NotEmpty String scriptSource)
throws ScriptException {
scriptLanguage =
Constraint.isNotNull(StringSupport.trimOrNull(engineName), "Scripting language can not be null or empty");
script = Constraint.isNotNull(StringSupport.trimOrNull(scriptSource), "Script source can not be null or empty");
initialize();
}
/**
* Constructor.
*
* @param scriptSource the script source
*
* @throws ScriptException thrown if the scripting engine supports compilation and the script does not compile
*/
public EvaluableScript(@Nonnull @NotEmpty String scriptSource)
throws ScriptException {
this("javascript", scriptSource);
}
/**
* Constructor.
*
* @param engineName the JSR-223 scripting engine name
* @param scriptSource the script source
*
* @throws ScriptException thrown if the script source file can not be read or the scripting engine supports
* compilation and the script does not compile
*/
public EvaluableScript(@Nonnull @NotEmpty String engineName, @Nonnull File scriptSource) throws ScriptException {
scriptLanguage =
Constraint.isNotNull(StringSupport.trimOrNull(engineName), "Scripting language can not be null or empty");
Constraint.isNotNull(scriptSource, "Script source file can not be null");
if (!scriptSource.exists()) {
throw new ScriptException("Script source file " + scriptSource.getAbsolutePath() + " does not exist");
}
if (!scriptSource.canRead()) {
throw new ScriptException("Script source file " + scriptSource.getAbsolutePath()
+ " exists but is not readable");
}
try {
script =
Constraint.isNotNull(StringSupport.trimOrNull(Files.toString(scriptSource, Charset.defaultCharset())),
"Script source can not be empty");
} catch (IOException e) {
throw new ScriptException("Unable to read data from source file " + scriptSource.getAbsolutePath());
}
initialize();
}
/**
* Gets the script source.
*
* @return the script source
*/
@Nonnull public String getScript() {
return script;
}
/**
* Gets the script language.
*
* @return the script source
*/
@Nonnull public String getScriptLanguage() {
return scriptLanguage;
}
/**
* Evaluates this script against the given bindings.
*
* @param scriptBindings the script bindings
*
* @return the result of the script or null if the script did not return a result
*
* @throws ScriptException thrown if there was a problem evaluating the script
*/
@Nullable public Object eval(Bindings scriptBindings) throws ScriptException {
if (compiledScript != null) {
return compiledScript.eval(scriptBindings);
} else {
return scriptEngine.eval(script, scriptBindings);
}
}
/**
* Evaluates this script against the given context.
*
* @param scriptContext the script context
*
* @return the result of the script or null if the script did not return a result
*
* @throws ScriptException thrown if there was a problem evaluating the script
*/
@Nullable public Object eval(ScriptContext scriptContext) throws ScriptException {
if (compiledScript != null) {
return compiledScript.eval(scriptContext);
} else {
return scriptEngine.eval(script, scriptContext);
}
}
/**
* Initializes the scripting engine and compiles the script, if possible.
*
* @throws ScriptException thrown if the scripting engine supports compilation and the script does not compile
*/
private void initialize() throws ScriptException {
ScriptEngineManager engineManager = new ScriptEngineManager();
scriptEngine = engineManager.getEngineByName(scriptLanguage);
Constraint.isNotNull(scriptEngine, "No scripting engine associated with scripting language " + scriptLanguage);
if (scriptEngine instanceof Compilable) {
compiledScript = ((Compilable) scriptEngine).compile(script);
} else {
compiledScript = null;
}
}
}