使用GSON序列化/反序列化json / object时的默认值

Question

I am using GSON for serialize and deserialize JSON/JAva Object for one of my application. I am using serializeNulls as some of my value need to be send as null to web service while some I don't want to be NULL. So what I tried in my setter/getter for which I don't need null that I have check that value is null or not, if its null then set the "" blank for it. But still when I am deserializing my object to json using gson.toJson() method its giving me null value for those.

private String mID;

public void setId(final String id) {
    if(id == null) {
        id = "";
    }
    mID = id;
}

public String getId() {
    if(mID == null) {
        mID = "";
    }
    return mID;
}

Gson gson = new GsonBuilder().serializeNulls().create();

Any idea how can i avoid null for some of the fields and set blank "" using setter/getter method or some other way.

Answer 1

You can do it using default value of mID and proper setter method

sample code:

class MyId{
    private String mID="";

    public void setId(final String id) {
        if(id != null) {
            mID = id;
        }
    }

    public String getId() {
        return mID;
    }
}

...
//JSON string to Object
MyId myId=new Gson().fromJson("{}", MyId.class);
System.out.println(new GsonBuilder().setPrettyPrinting().create().toJson(myId));

...
// Object to JSON string
MyId myId = new MyId();
System.out.println(new GsonBuilder().setPrettyPrinting().create().toJson(myId));

output:

{
   "mID": ""
}