org.directwebremoting.extend.ScriptBufferUtil Maven / Gradle / Ivy

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DWR is easy Ajax for Java. It makes it simple to call Java code directly from Javascript. It gets rid of almost all the boiler plate code between the web browser and your Java code.
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/*
 * Copyright 2005 Joe Walker
 *
 * 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.directwebremoting.extend;

import java.util.ArrayList;
import java.util.List;

import org.directwebremoting.ConversionException;
import org.directwebremoting.ScriptBuffer;

/**
 * A simple utility class to extract a {@link String} from a {@link ScriptBuffer}.
 * @author Joe Walker [joe at getahead dot ltd dot uk]
 */
public class ScriptBufferUtil
{
    /**
     * Ensure we can't be created
     */
    private ScriptBufferUtil()
    {
    }

    /**
     * Return a string ready for output.
     * @param buffer The source of the script data
     * @param converterManager How we convert script variable to Javascript
     * @return Some Javascript to be eval()ed by a browser.
     * @throws ConversionException If an error happens during parameter marshalling
     */
    public static String createOutput(ScriptBuffer buffer, ConverterManager converterManager) throws ConversionException
    {
        return createOutput(buffer, converterManager, false);
    }

    /**
     * Return a string ready for output.
     * @param script The source of the script data
     * @param converterManager How we convert script variable to Javascript
     * @param jsonOutput Are we doing strict JSON output?
     * @return Some Javascript to be eval()ed by a browser.
     * @throws ConversionException If an error happens during parameter marshalling
     */
    public static String createOutput(ScriptBuffer script, ConverterManager converterManager, boolean jsonOutput) throws ConversionException
    {
        OutboundContext context = new OutboundContext(jsonOutput);
        List scriptParts = new ArrayList();
        boolean outboundError = false;

        // First convert everything into OutboundVariables
        // TODO - something for IE 7 bug here?
        int variableCount = 0;
        for (Object part : script.getParts())
        {
            OutboundVariable ov = converterManager.convertOutbound(part, context);
            if (ov instanceof ErrorOutboundVariable)
            {
                outboundError = true;
            }

            scriptParts.add(ov);
            variableCount++;
        }

        StringBuilder buffer = new StringBuilder();

        // First we look for the declaration code
        for (OutboundVariable ov : scriptParts)
        {
            buffer.append(ov.getDeclareCode());
        }

        // Then we look for the construction code
        for (OutboundVariable ov : scriptParts)
        {
            buffer.append(ov.getBuildCode());
        }

        // Then we output everything else
        for (OutboundVariable ov : scriptParts)
        {
            String assignCode = ov.getAssignCode();
            if (assignCode == null)
            {
                throw new NullPointerException();
            }
            buffer.append(assignCode);
        }

        // Real JSON must be wrapped in { }
        String output = buffer.toString();
        if (jsonOutput && !output.startsWith("{") && !output.startsWith("["))
        {
            if (outboundError)
            {
                output = output.replaceFirst("null", "{}");
                output = "{\"error\":" + output + "}";
            }
            else
            {
                output = "{ \"reply\":" + output + "}";
            }
        }

        return output;
    }
}