WSO2数据服务返回XML而非JSON响应问题求助

我创建了一个WSO2数据服务，用于从PostgreSQL数据库获取产品列表，配置如下：

<data name="ProductListDS" serviceNamespace="" serviceGroup="" transports="http https">
  <description />
  <config id="ProductListDB">
    <property name="driverClassName">org.postgresql.Driver</property>
    <property name="url">jdbc:postgresql://localhost:5432/PRODUCTS</property>
    <property name="username">postgres</property>
    <property name="password">password123</property>
  </config>
  <operation name="QueryProductList">
    <call-query href="QueryProductList" />
  </operation>
  <resource method="GET" path="/products">
    <description />
    <call-query href="QueryProductList" />
  </resource>
  <query id="QueryProductList" useConfig="ProductListDB">
    <sql>SELECT service, name, amount
    FROM products;</sql>
   <result outputType="json">
   {
      "Products": {
         "Product": [
            {
               "service": "$service",
               "name": "$name",
               "amount": "$amount"
            }
         ]
      }
   }
</result>
   
  </query>
</data> 

我在API中通过Call Mediator调用该数据服务端点，期望获取JSON数据，调用逻辑如下：

<call>
    <endpoint key="getProductListEndpoint"/>
</call>
<property expression="$body" name="responsePayload" scope="default" type="STRING"/>
<log level="full">
    <property expression="get-property('responsePayload')" name="Response Payload"/>
</log>

但在日志中却得到了XML格式的响应：

[2023-09-02 10:15:56,147] INFO {LogMediator} - {api:project_list_api:v1.0.0} To: http://www.w3.org/2005/08/addressing/anonymous, WSAction: , SOAPAction: , MessageID: urn:uuid:542d3384-67e2-4831-bb71-c87bbdc270cc, correlation_id: ff3b8304-2e6a-4718-aca7-a88a8e222853, Direction: request, Response Payload = <soapenv:Body xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/"/>, Envelope: <soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/">soapenv:Body

return (<Products xmlns="http://ws.wso2.org/dataservice/QueryProductList"><Product><amount>12000</amount><service>Wireless</service><name>1 MONTH</name></Product><Product><amount>24000</amount><service>Wireless</service><name>2 MONTH</name></Product><Product><amount>36000</amount><service>Wireless</service><name>3 MONTH</name></Product><Product><amount>20000</amount><service>Cable</service><name>1 MONTH</name></Product><Product><amount>40000</amount><service>Cable</service><name>2 MONTH</name></Product><Product><amount>60000</amount><service>Cable</service><name>3 MONTH</name></Product></Products>)

</soapenv:Body></soapenv:Envelope>

请问为何未返回预期的JSON响应？

核心原因 #

问题出在Call Mediator默认调用的是数据服务的SOAP操作端点，而非你配置的REST风格/products资源。数据服务的SOAP操作端点默认返回XML格式，而你定义的JSON输出规则仅绑定在REST资源上。

具体解决方法 #

方法1：调用REST资源端点并指定Accept头

1. 调整getProductListEndpoint的URL，指向数据服务的REST资源路径：

   http://<WSO2服务器地址>:<端口>/services/ProductListDS/products
   

2. 在Call Mediator前添加请求头，明确要求JSON响应：

   <property name="Accept" value="application/json" scope="transport"/>
   <call>
       <endpoint key="getProductListEndpoint"/>
   </call>
   

方法2：修改数据服务操作，强制返回JSON

如果需要继续调用SOAP操作端点，可在数据服务的<operation>中指定输出格式：

<operation name="QueryProductList">
    <call-query href="QueryProductList">
        <with-output type="json"/>
    </call-query>
</operation>

这样即使通过SOAP协议调用，也会返回JSON格式响应。

方法3：在API中转换XML为JSON

若无法修改数据服务或端点配置，可在Call Mediator后添加转换逻辑，将XML响应转为JSON：

<call>
    <endpoint key="getProductListEndpoint"/>
</call>
<payloadFactory media-type="json">
    <format>
        {"Products": {"Product": $1}}
    </format>
    <args>
        <arg evaluator="xml" expression="//Products/Product"/>
    </args>
</payloadFactory>

内容的提问来源于stack exchange，提问作者Kavishka Rajapakshe