如何在WSO2 ESB中操纵本机Json？

Question

为了简化我的问题，假设我想用有效负载中的'd'替换所有'b'字符。

有没有一种方法可以让我原生地处理JSON数据，而不是首先将数据转换为XML？

我试图构建一个自定义的类中介来放入OutSequence中，但由于我只能访问MessageContext，它将有效负载视为XML，所以我遇到了问题。

"Destination": {
        "name": "abc",
        "type": "ST",
        "$": "\n"
     }

MessageContext.getEnvelope().getBody()

<Destination>
  <name>abc</name>
  <type>ST</type>
</Destination>

以在正常情况下传递内容（否则将在XML到JSON处理步骤中失败）。但必须有一种方法让我将数据操作为原生JSON（还是原生字符串？）也许能够获得输入流并从中操作数据？但我找不到从消息上下文到InputStream的方法？

Answer 1

WSO2本身已经编写了处理$字符的逻辑。

从他们的支持文档(https://docs.wso2.com/display/esb481/json+support):

在构建XML元素时，当“$”字符和数字作为JSON键的第一个字符出现时，ESB会以特殊的方式处理它们。

//    "$a" replace with "_JsonReader_PS_a"
private String replaceInvalidCharacters(String keyString){
    if(Pattern.compile("^[0-9]").matcher(keyString).find()) {
        return "_JsonReader_PD_" + keyString;
    } else if (keyString.startsWith("$")){
        return "_JsonReader_PS_" + keyString.substring(1);
    } else
        return keyString;
}

import java.io.BufferedReader;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;

import org.apache.axiom.om.OMElement;
import org.apache.axis2.AxisFault;
import org.apache.axis2.builder.Builder;
import org.apache.axis2.context.MessageContext;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.synapse.commons.json.JsonStreamBuilder;

/*
 * As WSO2 JSON parser can't handle single $ properties when converting between JSON and XML
 * This custom JSON Stream builder replaces all $ signs with the constant '_JsonReader_PS_',
 * which the WSO2 parser treats as a $ sign when transforming.
 */

public class CustomJsonStreamBuilder implements Builder {

private static final Log logger = LogFactory.getLog(CustomJsonStreamBuilder.class.getName());

JsonStreamBuilder jsonStreamBuilder = new JsonStreamBuilder();

public OMElement processDocument(InputStream arg0, String arg1, MessageContext arg2) throws AxisFault {

    logger.debug("Processing input stream for custom JSON stream builder");

    BufferedReader br = null;
    StringBuilder sb = new StringBuilder();

    String line;
    try {

        br = new BufferedReader(new InputStreamReader(arg0));
        while ((line = br.readLine()) != null) {
            sb.append(line);
        }

        String input = sb.toString();

        /*
         * WSO2 JSON parser treats _JsonReader_PS_ as $ in JSON structure
         */

        input = input.replace("$", "_JsonReader_PS_");
        InputStream is = new ByteArrayInputStream(input.getBytes("utf-8"));

        if (br != null) {
            try {
                br.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

        return jsonStreamBuilder.processDocument(is, arg1, arg2);

    } catch (Exception e) {
        e.printStackTrace();
        logger.error("Problem processing input stream for custom JSON stream builder", e);
    }

    return jsonStreamBuilder.processDocument(arg0, arg1, arg2);
}

}