core/src/main/java/flex/messaging/io/StatusInfoProxy.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF 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 flex.messaging.io;

import java.io.ByteArrayOutputStream;
import java.io.PrintWriter;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import javax.servlet.ServletException;

import flex.messaging.MessageException;

/**
 * Serializes a Throwable as a Status Info object. The object is sent
 * back to the client as an ActionScript object with the following
 * keys:
 * <ul>
 * <li>code: In 1.0, we always report this as &quot;Server.Processing&quot;. To be expanded in a future version.</li>
 * <li>description: The error message.</li>
 * <li>details: The error stack trace.</li>
 * <li>type: The error class name.</li>
 * <li>rootcause: If the exception was a ServletException, the rootcause will be included as a nested Status Info object.</li>
 * </ul>
 */
public class StatusInfoProxy extends AbstractProxy {
    static final long serialVersionUID = 8860353096401173320L;

    /**
     * Brief description of the error. This is intended to describe the
     * problem in a short manner that may be displayed to a human during
     * run-time of the client's application.
     */
    public static final String DESCRIPTION = "description";

    /**
     * Long description of the error. This may contain a verbose description
     * that may be provided to a more intelligent human for diagnosis.
     */
    public static final String DETAILS = "details";

    /**
     * The class name of the Throwable instance, if allowed to be
     * revealed to the client...
     */
    public static final String CLASS = "type";

    /**
     * Hierarchical dot "." string description of the problem.
     * <p>
     * The top error string shall be on of the following....
     * </p>
     * Client - Indicates the error was caused by something the client
     * did. Possibly the message was not well formed and/or did not
     * contain the proper information.
     * <p>
     * Server - Indicates the error was caused by something not directly
     * related to the contents of the message. Possibly the server could
     * not gain a needed resource or communicate with the desire WebService.
     * </p>
     * <p>VersionMismatch - The received AMF packet was of a version that
     * the Server does not recognize.
     * </p>
     * <p>The server can generate any number of sub errors to be attached to one
     * of the 3 above roots. The idea is that these strings provide an
     * intuitive description of where the problem happened and what it was.
     * Ultimately, finding and fixing the errors fast is the goal.
     * </p>
     */
    public static final String CODE = "code";

    public static final String ROOTCAUSE = "rootcause";

    public static final List propertyNameCache = new ArrayList();

    static {
        propertyNameCache.add(CODE);
        propertyNameCache.add(CLASS);
        propertyNameCache.add(DESCRIPTION);
        propertyNameCache.add(DETAILS);
        propertyNameCache.add(ROOTCAUSE);
    }

    protected boolean showStacktraces;

    public StatusInfoProxy() {
        super(null);
    }

    public StatusInfoProxy(Throwable defaultInstance) {
        super(defaultInstance);
    }

    public void setShowStacktraces(boolean value) {
        showStacktraces = value;
    }

    public String getAlias(Object instance) {
        // Status Info objects are anonymous
        return null;
    }

    public List getPropertyNames(Object instance) {
        return propertyNameCache;
    }

    public Class getType(Object instance, String propertyName) {
        Class type = null;

        if (CODE.equals(propertyName)) {
            type = String.class;
        } else if (CLASS.equals(propertyName)) {
            type = String.class;
        } else if (DESCRIPTION.equals(propertyName)) {
            type = String.class;
        } else if (DETAILS.equals(propertyName)) {
            type = String.class;
        } else if (ROOTCAUSE.equals(propertyName)) {
            type = Map.class;
        }

        return type;
    }

    public Object getValue(Object instance, String propertyName) {
        Object value = null;

        if (CODE.equals(propertyName)) {
            value = getCode(instance);
        } else if (CLASS.equals(propertyName)) {
            value = getType(instance);
        } else if (DESCRIPTION.equals(propertyName)) {
            value = getDescription(instance);
        } else if (DETAILS.equals(propertyName)) {
            value = getDetails(instance);
        } else if (ROOTCAUSE.equals(propertyName)) {
            value = getRootCause(instance);
        }

        return value;
    }

    public void setValue(Object instance, String propertyName, Object value) {
        return; // Throwable is essentially read-only
    }

    private String getCode(Object ex) {
        String code = null;
        if (ex instanceof MessageException) {
            code = ((MessageException) ex).getCode();
        }

        if (code == null) {
            code = "Server.Processing";
        }

        return code;
    }

    private String getType(Object ex) {
        String type = "";
        if (ex != null && showStacktraces) {
            type = ex.getClass().getName();
        }
        return type;
    }

    private String getDescription(Object ex) {
        String desc = null;
        if (ex instanceof Throwable) {
            desc = ((Throwable) ex).getMessage();
        }

        return desc;
    }

    private String getDetails(Object ex) {
        StringBuffer details = new StringBuffer();
        if (ex instanceof MessageException) {
            MessageException e = (MessageException) ex;
            if (e.getDetails() != null)
                details.append(e.getDetails());
        }

        if (showStacktraces && ex instanceof Throwable)
            details.append(getTraceback((Throwable) ex));

        return details.toString();
    }

    private Throwable getRootCauseException(Object ex) {
        if (ex == null)
            return null;

        if (ex instanceof ServletException) {
            ex = ((ServletException) ex).getRootCause();
        }

        if (ex instanceof Throwable)
            return ((Throwable) ex).getCause();
        else
            return null;
    }

    private Map getRootCause(Object ex) {
        Throwable t = getRootCauseException(ex);

        if (t != null)
            return getExceptionInfo(t);
        else
            return null;
    }

    private Map getExceptionInfo(Throwable t) {
        Map info = new HashMap();
        info.put(CODE, getCode(t));
        info.put(CLASS, getType(t));
        info.put(DESCRIPTION, getDescription(t));
        info.put(DETAILS, getDetails(t));
        info.put(ROOTCAUSE, t);
        return info;
    }

    private static String getTraceback(Throwable e) {
        String trace = "";

        if (e != null) {
            ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
            PrintWriter pr = new PrintWriter(outputStream);
            pr.println();
            e.printStackTrace(pr);
            pr.flush();
            trace = outputStream.toString();
        }

        return trace;
    }
}