Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Welcome To Ask or Share your Answers For Others

Categories

0 votes
298 views
in Technique[技术] by (71.8m points)

java - Setting default values to null fields when mapping with Jackson

I am trying to map some JSON objects to Java objects with Jackson. Some of the fields in the JSON object are mandatory(which I can mark with @NotNull) and some are optional.

After the mapping with Jackson, all the fields that are not set in the JSON object will have a null value in Java. Is there a similar annotation to @NotNull that can tell Jackson to set a default value to a Java class member, in case it is null?

Edit: To make the question more clear here is some code example.

The Java object:

class JavaObject {
    @NotNull
    public String notNullMember;

    @DefaultValue("Value")
    public String optionalMember;
}

The JSON object can be either:

{
    "notNullMember" : "notNull"
}

or:

{
    "notNullMember" : "notNull",
    "optionalMember" : "optional"
}

The @DefaultValue annotations is just to show what I am asking. It's not a real annotation. If the JSON object is like in the first example I want the value of the optionalMember to be "Value" and not null. Is there an annotation that does such a thing?

See Question&Answers more detail:os

与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
Welcome To Ask or Share your Answers For Others

1 Reply

0 votes
by (71.8m points)

There is no annotation to set default value.
You can set default value only on java class level:

public class JavaObject 
{
    public String notNullMember;

    public String optionalMember = "Value";
}

与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
OGeek|极客中国-欢迎来到极客的世界,一个免费开放的程序员编程交流平台!开放,进步,分享!让技术改变生活,让极客改变未来! Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Click Here to Ask a Question

...