使用最新的Jackson解析器库在Android设备上解析JSON

Question

Here is example of JSON response str:

{"myServiceMethodResult":[{"BoolPropertyOfFooClass":false,"StringPropertyOfFooClass":"tstString", "Bar":[{"BoolPropertyOfBarClass":false,"StringProperyOfBarClass":"tst"}]
}]
}

Service is returning List

List<Foo> myServiceMethod(){

return new List<Foo> myFooList
}

This are the classes:

@JsonRootName(value = "myServiceMethodResult")
Class Foo{

public boolean BoolPropertyOfFooClass
public String  StringPropertyOfFooClass


@JsonProperty(value = "Bar")
public List<Bar> myBar;


public boolean getBoolPropertyOfFooClass(){

return BoolPropertyOfFooClass;
}

public void setBoolPropertyOfFooClass(bool value){
this.BoolPropertyOfFooClass = value

}

public String getStringPropertyOfFooClass(){

return StringPropertyOfFooClass;
}

public void setBoolPropertyOfFooClass(String value){
this.StringPropertyOfFooClass = value

}

public List<Bar> myBar() {
        return myBar;
    }

    public void setmyBar(List<Bar> value) {
        this.myBar= value;
    }

}

I'm usign Jackson parser and first of all Parsing JSON string to an object is surprising slow (despite a fact that this file is huge (2 MB)

  String jsonStr = sh.makeServiceCall(serviceUrl/MethodName, ServiceHandler.POST, json_content_parameters);

       ObjectMapper mapper = new ObjectMapper();
       mapper.configure(DeserializationFeature.UNWRAP_ROOT_VALUE, true);
       JsonNode node = null;
     myFooInstance=  mapper.readValue(new StringReader(jsonStr), new TypeReference<List<Foo>>(){}); 

mapper.readValue is hitting exception myServiceResult does not match expected ('List'). Further more, if I'm using readTree function it takes 5 seconds (but not hittign exception). Is there any better way of getting Object faster,

Further more I'm not able to figure how to map List of Bar objects inside my Foo objects. I'm able to set my properties using this line of code:

TypeReference<List<Foo>> typeRef = new TypeReference<List<Foo>>(){};
myInstanceFoo= mapper.readValue(node.traverse(), typeRef);

So I Have my List of Foo objects but I'm not able to get List inside of list using something simmilar. Any help about problems with duration, or setting inner List object would be appreciated

Trace:

com.fasterxml.jackson.databind.JsonMappingException: Root name 'MyMethodResponse' does not match expected ('List') for type [collection type; class java.util.List, contains [simple type, class com.package.Foo]]
 at [Source: java.io.StringReader@411dc790; line: 1, column: 2]

Answer 1

Since it appears that you have the response wrapped in a single-member object instance, you have the option of annotating your Foo class with this:

@JsonRootName("MyMethodResponse")

IMPORTANT: the name is FIXED.

However you are not done yet. You need to configure your ObjectMapper to use this annotation:

mapper.configure(DeserializationFeature.UNWRAP_ROOT_VALUE);

Your have another problem. Namely, your List<Bar> has name myBar in your POJO, but Bar in the produced JSON. You need to annotate your myBar field with @JsonProperty :

@JsonProperty("Bar")

Answer 2

In case Someone stumbles on a same problem I figured it out. To serialize Foo class if JSON is in format

{"response":[{"propertyOfFooClass":"something"
}]
} 

you nedd to Create Root Class that contains list of Foo Class

public class RootWrapper {

private List<Foo> foo;

public List<Foo> getFoos() {
    return channels;
}

@JsonProperty("response")
public void setFoos(List<Foo> fooList) {
    this.foo= fooList;
}


RootWrapper mj = mapper.readValue(jsonStr, RootWrapper.class);

Cheers