Transformer Örneği

DomSourceToStringNoErrorTransformer.java

package com.yamanyar.si.transformers.DomSourceToStringNoErrorTransformer; 

import org.apache.log4j.Logger;
import org.springframework.integration.Message;
import org.springframework.integration.support.MessageBuilder;
import org.springframework.integration.transformer.Transformer;

import javax.xml.transform.OutputKeys;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;
import java.io.StringWriter;

/**
 * This transformer changes and DomSource payload to a message with string representation.
 * The reason it has "NoError" in it's name is; it never throws an error. If an error occurs, this only logged
 * and toString() of original payload is used. It's assumed that the receiver/sender will handle the situation.
 * <p/>
 * This transformer is designed to be used with transforming DomSource messages to String Messages for LOGGING. That's why error handling is such simple.
 *
 * @author Kaan Yamanyar
 */
public class DomSourceToStringNoErrorTransformer implements Transformer {

    private static final Logger logger = Logger.getLogger(DomSourceToStringNoErrorTransformer.class);


    public Message<?> transform(Message<?> message) {
        Object messagePayloadObject = message.getPayload();

        try {
            DOMSource payload = (DOMSource) messagePayloadObject;

            javax.xml.transform.Transformer transformer = TransformerFactory.newInstance().newTransformer();
            transformer.setOutputProperty(OutputKeys.INDENT, "yes");
            StreamResult result = new StreamResult(new StringWriter());

            transformer.transform(payload, result);

            String payloadAsString = result.getWriter().toString();

            message = MessageBuilder.withPayload(payloadAsString)
                    .copyHeaders(message.getHeaders())
                    .build();

        } catch (Exception e) {

            //is there payload? is it null? (with si 2.1 it's impossible)
            //if it is an other object rather than what we are expecting; maybe toString method is badly written; cover it:
            String payload;
            try {
                payload = (messagePayloadObject != null) ? messagePayloadObject.toString() : "Empty Payload (null)!";
            } catch (Exception toStringError) {
                logger.error("A payload with a badly written toString()", toStringError);
                //still ignore; this transformation is only for logging
                payload = "Payload with bad toString()";
            }

            message = MessageBuilder.withPayload(payload)
                    .copyHeaders(message.getHeaders())
                    .build();

            //this should not be reached; it it is there is an design problem with the flow:
            logger.error("An error occurred while transforming DomSource to String. Due to nature of this transformer; this error will be ignored.", e);
        }

        return message;
    }
}