com.github.markusbernhardt.proxy.selector.pac.JavaxPacScriptParser Maven / Gradle / Ivy

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package com.github.markusbernhardt.proxy.selector.pac;

import java.lang.reflect.Method;

import org.mozilla.javascript.Undefined;

import com.github.markusbernhardt.proxy.util.Logger;
import com.github.markusbernhardt.proxy.util.Logger.LogLevel;

import delight.rhinosandox.RhinoSandbox;
import delight.rhinosandox.RhinoSandboxes;

/*****************************************************************************
 * PAC parser using the Rhino JavaScript engine bundled with Java 1.6

 * 
 * More information about PAC can be found there:

 * Proxy_auto-config 

 * 
 * web-browser-auto-proxy-configuration
 * 
 * @author Markus Bernhardt, Copyright 2016
 * @author Bernd Rosstauscher, Copyright 2009
 ****************************************************************************/
public class JavaxPacScriptParser implements PacScriptParser {
    static final String SCRIPT_METHODS_OBJECT = "__pacutil";

    static final String SOURCE_NAME = JavaxPacScriptParser.class.getName();

    private final PacScriptSource source;

    private final RhinoSandbox engine;

    /*************************************************************************
     * Constructor
     * 
     * @param source
     *            the source for the PAC script.
     * @throws ProxyEvaluationException
     *             on error.
     ************************************************************************/
    public JavaxPacScriptParser(PacScriptSource source) throws ProxyEvaluationException {
        this.source = source;
        this.engine = setupEngine();
    }

    /*************************************************************************
     * Initializes the JavaScript engine and adds aliases for the functions defined in ScriptMethods.
     * 
     * @throws ProxyEvaluationException
     *             on error.
     ************************************************************************/
    private RhinoSandbox setupEngine() throws ProxyEvaluationException {
        RhinoSandbox rhinoSandbox = RhinoSandboxes.create();
        rhinoSandbox.inject(SCRIPT_METHODS_OBJECT, new PacScriptMethods());
        // allow String
        rhinoSandbox.allow(String.class);

        Class scriptMethodsClazz = ScriptMethods.class;
        Method[] scriptMethods = scriptMethodsClazz.getMethods();

        for (Method method : scriptMethods) {
            String name = method.getName();
            int args = method.getParameterTypes().length;
            StringBuilder toEval = new StringBuilder(name).append(" = function(");
            for (int i = 0; i < args; i++) {
                if (i > 0) {
                    toEval.append(",");
                }
                toEval.append("arg").append(i);
            }
            toEval.append(") {return ");

            String functionCall = buildFunctionCallCode(name, args);

            // If return type is java.lang.String convert it to a JS string
            if (String.class.isAssignableFrom(method.getReturnType())) {
                functionCall = "String(" + functionCall + ")";
            }
            toEval.append(functionCall).append("; }");
            try {
                // Add functions with calls to Java object to global scope
                rhinoSandbox.evalWithGlobalScope(SOURCE_NAME, toEval.toString());
            }
            catch (Exception e) {
                Logger.log(getClass(), LogLevel.ERROR, "JS evaluation error when creating alias for " + name + ".", e);
                throw new ProxyEvaluationException("Error setting up script engine", e);
            }
        }

        return rhinoSandbox;
    }

    /*************************************************************************
     * Builds a JavaScript code snippet to call a function that we bind.
     * 
     * @param functionName
     *            of the bound function
     * @param args
     *            of the bound function
     * @return the JS code to invoke the method.
     ************************************************************************/

    private String buildFunctionCallCode(String functionName, int args) {
        StringBuilder functionCall = new StringBuilder();
        functionCall.append(SCRIPT_METHODS_OBJECT).append(".").append(functionName).append("(");
        for (int i = 0; i < args; i++) {
            if (i > 0) {
                functionCall.append(",");
            }
            functionCall.append("arg").append(i);
        }
        functionCall.append(")");
        return functionCall.toString();
    }

    /***************************************************************************
     * Gets the source of the PAC script used by this parser.
     * 
     * @return a PacScriptSource.
     **************************************************************************/
    @Override
    public PacScriptSource getScriptSource() {
        return this.source;
    }

    /*************************************************************************
     * Evaluates the given URL and host against the PAC script.
     * 
     * @param url
     *            the URL to evaluate.
     * @param host
     *            the host name part of the URL.
     * @return the script result.
     * @throws ProxyEvaluationException
     *             on execution error.
     ************************************************************************/
    @Override
    public String evaluate(String url, String host) throws ProxyEvaluationException {
        try {
            StringBuilder script = new StringBuilder(this.source.getScriptContent());
            String evalMethod = " ;FindProxyForURL (\"" + url + "\",\"" + host + "\")";
            script.append(evalMethod);
            Object result = this.engine.eval(SOURCE_NAME, script.toString());
            if (Undefined.isUndefined(result)) {
                return null;
            }
            return (String) result;
        }
        catch (Exception e) {
            Logger.log(getClass(), LogLevel.ERROR, "JS evaluation error.", e);
            throw new ProxyEvaluationException("Error while executing PAC script: " + e.getMessage(), e);
        }

    }
}