Mule - java.lang.String cannot be cast to java.util.Map

Question

I want to write a mule application which will read the database for unprocessed records, club them in JSON payload format and then hit a REST webservice. I am able to read the records from the database and able to convert the database records in JSON. However, whenever I run the application I am getting following exception

java.lang.ClassCastException: java.lang.String cannot be cast to java.util.Map

Here is my Mule configuration XML

<?xml version="1.0" encoding="UTF-8"?>

<mule xmlns:db="http://www.mulesoft.org/schema/mule/db" xmlns:json="http://www.mulesoft.org/schema/mule/json" xmlns:http="http://www.mulesoft.org/schema/mule/http" xmlns="http://www.mulesoft.org/schema/mule/core" xmlns:doc="http://www.mulesoft.org/schema/mule/documentation"
    xmlns:spring="http://www.springframework.org/schema/beans" 
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-current.xsd
http://www.mulesoft.org/schema/mule/core http://www.mulesoft.org/schema/mule/core/current/mule.xsd
http://www.mulesoft.org/schema/mule/db http://www.mulesoft.org/schema/mule/db/current/mule-db.xsd
http://www.mulesoft.org/schema/mule/json http://www.mulesoft.org/schema/mule/json/current/mule-json.xsd
http://www.mulesoft.org/schema/mule/http http://www.mulesoft.org/schema/mule/http/current/mule-http.xsd">
    <db:mysql-config name="MySQL_Configuration" host="localhost" port="3306" user="root" database="my_database_name" doc:name="MySQL Configuration"/>
    <http:request-config name="HTTP_Request_Configuration" protocol="HTTPS" host="example.net" port="8000" basePath="API" doc:name="HTTP Request Configuration"/>
    <flow name="cwg_clientFlow">
        <poll doc:name="Poll">
            <db:select config-ref="MySQL_Configuration" doc:name="Database">
                <db:parameterized-query><![CDATA[SELECT * FROM cwg_ws_data WHERE SyncFlag = 0]]></db:parameterized-query>
            </db:select>
        </poll>
        <logger message="#[payload]" level="INFO" doc:name="Logger"/>
        <json:object-to-json-transformer   doc:name="Object to JSON" />
        <logger message="JSON Payload is #[payload]" level="INFO" doc:name="Logger"/>
        <http:request config-ref="HTTP_Request_Configuration" path="/cwg" method="POST" doc:name="HTTP">
            <http:request-builder>
                <http:query-params expression="#[payload]"/>
                <http:header headerName="access_token" value="MQTgpMUmyQLt134maB6vPp6oWFgMtGsqzIlpCN74"/>
            </http:request-builder>
        </http:request>
        <logger message="webservice response #[payload]" level="INFO" doc:name="Logger"/>
    </flow>
</mule>

I am unable to understand where it is going wrong

Please help me, I am trying this since last 2 days.

Thanks in advance

-Paresh (kendreparesh@gmail.com)

Answer 1

Try removing this line.

<http:query-params expression="#[payload]"/>

It should work. As your payload is Json String and you are trying to map it to Query params which expects Map. Also for POST your payload will converted to body.