Nested JSON to Java Object mapping using GSON

Question

Hello I am stuck in converting JSON NESTED Array to JAVA Objects using GSON labirary.

Here is my JSON String

[{\"name\":\"3214657890RootSAPSSE\",\"children\":[{\"name\":\"672BENIAMEEN .Sales Base Market SectionCustomer Representative\"},{\"name\":\"672BENIAMEEN .Sales Base Market SectionPeão\"}]}]

I tested my code with x="[{\"name\":\"MyNode\"}]"; and for this my java code is

Gson gson = new Gson(); 
java.lang.reflect.Type type = new TypeToken<List<EmployeeJSONObj>>(){}.getType();
List<EmployeeJSONObj>l = gson.fromJson(x, type);
System.out.println("hello "+l.get(0).getName());

AND EmployeeJSONObj is class

public class EmployeeJSONObj {
    private String name;
    EmployeeJSONObj()
    {

    }
    public String getName()
    {
        return name;
    }

}

This is working fine. But my this code gives me error when I change the JSON String to

[{\"name\":\"3214657890RootSAPSSE\",\"children\":[{\"name\":\"672BENIAMEEN .Sales Base Market SectionCustomer Representative\"},{\"name\":\"672BENIAMEEN .Sales Base Market SectionPeão\"}]}]

This is a tree. I want generic solution, which can traverse the whole nested json string. I'm stuck in the middle of a project. Please help me to solve this.

Thanks

Does it always have children?

Sotirios Delimanolis
– Sotirios Delimanolis

2013-09-20 12:47:59 +00:00
Commented Sep 20, 2013 at 12:47 — Sotirios Delimanolis
– Sotirios Delimanolis, Commented Sep 20, 2013 at 12:47

Sotirios Delimanolis · Accepted Answer · 2013-09-20 12:52:16Z

1

You need a List of children in your class so that Gson can deserialize the children array. Here's a working example.

public static void main(String args[]) {
    String str = "[{\"name\":\"3214657890RootSAPSSE\",\"children\":[{\"name\":\"672BENIAMEEN .Sales Base Market SectionCustomer Representative\"},{\"name\":\"672BENIAMEEN .Sales Base Market SectionPeão\"}]}]";
    System.out.println(str);

    Gson gson = new Gson(); 
    java.lang.reflect.Type type = new TypeToken<List<EmployeeJSONObj>>(){}.getType();
    List<EmployeeJSONObj>l = gson.fromJson(str, type);
    System.out.println(l);
}
public static  class EmployeeJSONObj {
    private String name;
    private List<EmployeeJSONObj> children = new LinkedList<>();
    EmployeeJSONObj()
    {

    }
    public String getName()
    {
        return name;
    }

    public String toString() {
        return "name: " + name + ", children = " + children;
    }

}

prints

[{"name":"3214657890RootSAPSSE","children":[{"name":"672BENIAMEEN .Sales Base Market SectionCustomer Representative"},{"name":"672BENIAMEEN .Sales Base Market SectionPeão"}]}]
[name: 3214657890RootSAPSSE, children = [name: 672BENIAMEEN .Sales Base Market SectionCustomer Representative, children = [], name: 672BENIAMEEN .Sales Base Market SectionPeão, children = []]]

answered Sep 20, 2013 at 12:52

Sotirios Delimanolis

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15 Comments

user2777070 Over a year ago

I think thi is not working for nested json - I mean My json is generating dynamically. So user can make as many child as she wants...

Sotirios Delimanolis Over a year ago

@user2777070 Provide an example that you think won't work. Each EmployeeJSONObj has its own children. It'll nest as many as it needs to.

user2777070 Over a year ago

When I give it dynamic JSON it gives me this error "Expected BEGIN_ARRAY but was STRING at line 1 column 2"

Sotirios Delimanolis Over a year ago

@user2777070 You're trying a different format of JSON than in your example. You're giving it an object instead of an array.

user2777070 Over a year ago

How do I get the stored objects in java from this code? istead of showing whole json string?

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