执行表达式失败.(org.mule.api.expression.ExpressionRuntimeException)

Question

我正在尝试创建一个简单的mule应用程序，它读取磁盘上文件的名称和内容并在web浏览器上显示。

我的流程如下HTTP -> JAVA TRANSFORMER - SETPAYLOAD - HTTP

我的Java转换器代码包括以下

public class ReadFile extends AbstractMessageTransformer {
    /**
     * loads the content of the file specified in the parameter
     * 
     * @param filename
     *            the name of the file
     * @return the content of the file
     */
    public String readFile(String filename) {
        File file;
        file = new File("O:\test.txt");
        StringBuilder builder = new StringBuilder();
        BufferedReader reader = null;
        try {
            reader = new BufferedReader(new FileReader(file));
            String line = null;
            while ((line = reader.readLine()) != null)
                builder.append(line);
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            closeQuietly(reader);
        }
        return builder.toString();
    }
    public String getFileName(MuleMessage message) {
        Path p = Paths.get("O:\Test.txt");
        String file = p.getFileName().toString();
        return file;
    }
    public String setPayload(MuleMessage message, String outputEncoding) {
        String payload1 = "#[ReadFile]";
        return payload1;
    }
    private void closeQuietly(Closeable c) {
        if (c != null) {
            try {
                c.close();
            } catch (IOException ignored) {
            }
        }
    }
    @Override
    public Object transformMessage(MuleMessage message, String outputEncoding)
            throws TransformerException {
        String filename = getFileName(message);
        String content = readFile(filename);
        setPayload(message, content);
        return message;
    }
}

我得到错误执行表达式ReadFile失败。(org.mule.api.expression.ExpressionRuntimeException)。消息负载类型为:String

却不知道为什么?

Answer 1

你在setPayload方法中犯了一个小错误。没有添加文件内容到MuleMessage。像下面这样做就可以了

public String setPayload(MuleMessage message, String outputEncoding) {
    message.setPayload(outputEncoding);
    //String payload1 = "#[ReadFile]";
    return null;
}

和我的流程看起来像下面(我已经实现了onCallable方法)

 <flow name="filetestFlow1">
    <http:listener config-ref="HTTP_Listener_Configuration" path="/" doc:name="HTTP"/>
    <logger message="--- Service triggred --" level="INFO" doc:name="Logger"/>
    <component class="filetest.ReadFile" doc:name="Java"/>
</flow>