Posting JSON to REST API

curl, jackson, json, rest, spring

Solution

As sdouglass suggested, Spring MVC automatically detects Jackson and sets up a MappingJacksonHttpMessageConverter to handle conversion to/from JSON. But I did need explicity configure the converter to get it to work as he also pointed out.

I added the following and my CURL GET requests were working..Hooray.

AppConfig.java

@Configuration
@ComponentScan(basePackages = "com.app")
public class AppConfig {

    @Bean
    public AnnotationMethodHandlerAdapter annotationMethodHandlerAdapter()
    {
        final AnnotationMethodHandlerAdapter annotationMethodHandlerAdapter = new AnnotationMethodHandlerAdapter();
        final MappingJacksonHttpMessageConverter mappingJacksonHttpMessageConverter = new MappingJacksonHttpMessageConverter();

        HttpMessageConverter<?>[] httpMessageConverter = { mappingJacksonHttpMessageConverter };

        String[] supportedHttpMethods = { "POST", "GET", "HEAD" };

        annotationMethodHandlerAdapter.setMessageConverters(httpMessageConverter);
        annotationMethodHandlerAdapter.setSupportedMethods(supportedHttpMethods);

        return annotationMethodHandlerAdapter;
    }
}

curl -i -H "Content-Type:application/json" -H "Accept:application/json" http://localhost:8080/PurchaseAPIServer/api/purchase

HTTP/1.1 200 OK
Server: Apache-Coyote/1.1
Content-Type: application/json
Transfer-Encoding: chunked
Date: Thu, 26 Apr 2012 21:19:55 GMT

[{"id":1,"pan":111}]

But the following CURL POST was still not working (Never hitting the controller action and giving no console debug info.

curl -i -X POST -H "Content-Type:application/json"  http://localhost:8080/PurchaseAPIServer/api/purchaseMe -d "{"id":2,"pan":122}"

HTTP/1.1 400 Bad Request
Server: Apache-Coyote/1.1
Content-Type: text/html;charset=utf-8
Content-Length: 971
Date: Thu, 26 Apr 2012 21:29:56 GMT
Connection: close

The request sent by the client was syntactically incorrect ().

So I added Logback to get some detailed debugging started.

<configuration>

    <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
        <encoder>
            <pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n
            </pattern>
        </encoder>
    </appender>

    <appender name="FILE" class="ch.qos.logback.core.FileAppender">
        <file>/home/thomas/springApps/purchaseapi.log</file>
        <encoder>
            <pattern>%date %level [%thread] %logger{10} [%file:%line] %msg%n
            </pattern>
        </encoder>
    </appender>

    <logger name="org.hibernate" level="DEBUG" />

    <logger name="org.springframework" level="TRACE" />
    <logger name="org.springframework.transaction" level="INFO" />
    <logger name="org.springframework.security" level="INFO" /> <!-- to debug security related issues (DEBUG) -->
    <logger name="org.springframework.web.servlet.mvc" level="TRACE" /> <!-- some serialization issues are at trace level here: org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod -->

    <!-- our service -->
    <logger name="com.app" level="DEBUG" />
    <!-- <logger name="com.app" level="INFO" /> --><!-- to follow if setup is being executed -->

    <root level="INFO">
        <appender-ref ref="FILE" />
    </root>

</configuration>

Adding TRACE level debugging to org.springframework.web.servlet.mvc gave me the answer to the problem.

2012-04-28 14:17:44,579 DEBUG [http-bio-8080-exec-3] o.s.w.s.m.m.a.RequestResponseBodyMethodProcessor [AbstractMessageConverterMethodArgumentResolver.java:117] Reading [com.app.model.Purchase] as "application/json" using [org.springframework.http.converter.json.MappingJacksonHttpMessageConverter@74a14fed]
2012-04-28 14:17:44,604 TRACE [http-bio-8080-exec-3] o.s.w.s.m.m.a.ServletInvocableHandlerMethod [InvocableHandlerMethod.java:159] Error resolving argument [0] [type=com.app.model.Purchase]
HandlerMethod details: 
Controller [com.app.controller.PurchaseController]
Method [public void com.app.controller.PurchaseController.create(com.app.model.Purchase)]

org.springframework.http.converter.HttpMessageNotReadableException: Could not read JSON: Unexpected character ('p' (code 112)): was expecting double-quote to start field name

I changed my CURL POSTs to the following an it all worked:

curl -i -X POST -H "Content-Type:application/json" http://localhost:8080/PurchaseAPIServer/api/purchase -d '{"pan":11111}'
HTTP/1.1 201 Created
Server: Apache-Coyote/1.1
Content-Length: 0
Date: Sat, 28 Apr 2012 13:19:40 GMT

Hopefully someone finds this useful.

Problem

Original source