WSO2 EI调用HTTP接口遇JSON解析错误，如何处理多内容类型？

调用时出现错误：

Unexpected character '{' (code 123) in prolog; expected '<'

直接通过curl调用该端点的结果：

*   Trying IP:PORT...
* TCP_NODELAY set
* Connected to ...
> POST /source.html HTTP/1.1
> Host: IP:PORT
> User-Agent: curl/7.68.0
> Accept: */*
> Content-Type: application/x-www-form-urlencoded
> Content-Length: 63
>
* upload completely sent off: 63 out of 63 bytes
* Mark bundle as not supporting multiuse
< HTTP/1.1 200 OK
< Server: Mule EE Core Extensions/3.9.5-20230823
< Set-Cookie: Stick=R2583989947; Domain=trionline.iic.local; Path=/
< Transfer-Encoding: chunked
< Content-Type: text/json; charset=utf-8
< Date: Mon, 01 Jan 2024 10:19:52 GMT
< Keep-Alive: false
< http.version: HTTP/1.1

< X-Powered-By: Servlet/2.5 JSP/2.1
< http.status: 200
< http.request: .../resource.html
< http.headers: {Transfer-Encoding=chunked, Keep-Alive=false, Connection=false, Set-Cookie= 
[Lorg.apache.commons.httpclient.Cookie;@1f6ae621, Date=Mon, 01 Jan 2024 10:19:52 GMT, X- 
Powered-By=Servlet/2.5 JSP/2.1, Content-Type=text/json; charset=utf-8}
< http.method: POST
< http.query.params: {}
< http.query.string:
< Connection: close
<
* Closing connection 0{"token":"..."}

报错核心原因：WSO2 EI默认对未识别的内容类型按XML解析，而该端点返回的text/json未被EI识别为JSON类型，导致解析JSON起始符{时触发XML解析错误。以下是处理不同内容类型的具体方案：

解决方案 #

1. 全局配置添加text/json识别 #

编辑EI安装目录下的repository/conf/synapse.properties，找到synapse.commons.json.input.types属性，将text/json加入JSON类型列表：

synapse.commons.json.input.types=application/json,text/json

此配置让EI自动把text/json响应当作JSON处理，无需额外转换。

2. 配置消息构建器与格式化器 #

在repository/conf/message-builders.xml中添加text/json对应的JSON解析器：

<messageBuilder contentType="text/json" class="org.apache.synapse.commons.json.JsonStreamBuilder"/>

在repository/conf/message-formatters.xml中添加对应的输出格式化器：

<messageFormatter contentType="text/json" class="org.apache.synapse.commons.json.JsonStreamFormatter"/>

确保EI能正确解析和输出text/json类型的消息。

3. 通过序列动态转换内容类型 #

若无法修改全局配置，可在API/代理服务的响应流(outFlow)中添加序列，动态将text/json替换为application/json：

<sequence xmlns="http://ws.apache.org/ns/synapse" name="TextJsonConverter">
    <property name="transport_content_type" expression="get-property('transport', 'Content-Type')" scope="default"/>
    <filter source="$ctx:transport_content_type" regex="text/json">
        <then>
            <property name="CONTENT_TYPE" value="application/json" scope="transport"/>
        </then>
    </filter>
</sequence>

将该序列关联到API的outFlow：

<api xmlns="http://ws.apache.org/ns/synapse" name="YourAPI" context="/your-api">
    <outFlow>
        <sequence key="TextJsonConverter"/>
        <send/>
    </outFlow>
    <!-- 其他API配置 -->
</api>

4. 端点级别强制指定消息类型 #

在HTTP端点配置中，强制指定响应按JSON处理：

<endpoint xmlns="http://ws.apache.org/ns/synapse" name="TargetEndpoint">
    <http uri="http://IP:PORT/source.html">
        <property name="messageType" value="application/json" scope="axis2"/>
    </http>
</endpoint>

此配置忽略原始Content-Type头，直接按JSON解析响应。

内容的提问来源于stack exchange，提问作者behzad