How to determine if a JSON key has been set to null or not provided

I am using gson to convert JSON to my POJO. If I am not passing a specific parameter (the whole parameter, not just the value) in my JSON, it is automatically initialized as null.
Is there a way to find out difference between the above null and the null I get, when I am passing that parameter value as null.

P.S. I cannot change the default conversion from JSON to POJO

asked Nov 20 '18 at 1:07

Yash Bansal

466

not passing a specific parameter means passing "" ? or passing "{}" ?

– xxy
Nov 20 '18 at 1:09

Why do you need to know this? Won't the result be the same anyway?

– Phil
Nov 20 '18 at 1:12

@xxy I think he means like having fields "foo" and "bar" and only passing {"foo":"foo"} (no bar)

– Phil
Nov 20 '18 at 1:13

Thanks for commenting. Not passing that field means: { 'title': 'ComputingandInformationsystems', 'id': 1, 'children': 'true' } In the above JSON, two cases: Case 1: Not passing: { 'id': 1, 'children': 'true' } Case 2: Passing null { 'title': null, 'id': 1, 'children': 'true' }

– Yash Bansal
Nov 20 '18 at 1:21

@Phil: I need to know them, as both the scenarios are different and I need to handle them differently

– Yash Bansal
Nov 20 '18 at 1:28

add a comment |

P.S. I cannot change the default conversion from JSON to POJO

asked Nov 20 '18 at 1:07

Yash Bansal

466

not passing a specific parameter means passing "" ? or passing "{}" ?

– xxy
Nov 20 '18 at 1:09

Why do you need to know this? Won't the result be the same anyway?

– Phil
Nov 20 '18 at 1:12

@xxy I think he means like having fields "foo" and "bar" and only passing {"foo":"foo"} (no bar)

– Phil
Nov 20 '18 at 1:13

Thanks for commenting. Not passing that field means: { 'title': 'ComputingandInformationsystems', 'id': 1, 'children': 'true' } In the above JSON, two cases: Case 1: Not passing: { 'id': 1, 'children': 'true' } Case 2: Passing null { 'title': null, 'id': 1, 'children': 'true' }

– Yash Bansal
Nov 20 '18 at 1:21

@Phil: I need to know them, as both the scenarios are different and I need to handle them differently

– Yash Bansal
Nov 20 '18 at 1:28

add a comment |

P.S. I cannot change the default conversion from JSON to POJO

asked Nov 20 '18 at 1:07

Yash Bansal

466

P.S. I cannot change the default conversion from JSON to POJO

java json

asked Nov 20 '18 at 1:07

Yash Bansal

466

asked Nov 20 '18 at 1:07

Yash Bansal

466

asked Nov 20 '18 at 1:07

Yash Bansal

466

asked Nov 20 '18 at 1:07

Yash Bansal

466

asked Nov 20 '18 at 1:07

Yash Bansal

466

not passing a specific parameter means passing "" ? or passing "{}" ?

– xxy
Nov 20 '18 at 1:09

Why do you need to know this? Won't the result be the same anyway?

– Phil
Nov 20 '18 at 1:12

@xxy I think he means like having fields "foo" and "bar" and only passing {"foo":"foo"} (no bar)

– Phil
Nov 20 '18 at 1:13

Thanks for commenting. Not passing that field means: { 'title': 'ComputingandInformationsystems', 'id': 1, 'children': 'true' } In the above JSON, two cases: Case 1: Not passing: { 'id': 1, 'children': 'true' } Case 2: Passing null { 'title': null, 'id': 1, 'children': 'true' }

– Yash Bansal
Nov 20 '18 at 1:21

@Phil: I need to know them, as both the scenarios are different and I need to handle them differently

– Yash Bansal
Nov 20 '18 at 1:28

add a comment |

not passing a specific parameter means passing "" ? or passing "{}" ?

– xxy
Nov 20 '18 at 1:09

Why do you need to know this? Won't the result be the same anyway?

– Phil
Nov 20 '18 at 1:12

@xxy I think he means like having fields "foo" and "bar" and only passing {"foo":"foo"} (no bar)

– Phil
Nov 20 '18 at 1:13

Thanks for commenting. Not passing that field means: { 'title': 'ComputingandInformationsystems', 'id': 1, 'children': 'true' } In the above JSON, two cases: Case 1: Not passing: { 'id': 1, 'children': 'true' } Case 2: Passing null { 'title': null, 'id': 1, 'children': 'true' }

– Yash Bansal
Nov 20 '18 at 1:21

@Phil: I need to know them, as both the scenarios are different and I need to handle them differently

– Yash Bansal
Nov 20 '18 at 1:28

not passing a specific parameter means passing "" ? or passing "{}" ?

– xxy
Nov 20 '18 at 1:09

Why do you need to know this? Won't the result be the same anyway?

– Phil
Nov 20 '18 at 1:12

@xxy I think he means like having fields "foo" and "bar" and only passing {"foo":"foo"} (no bar)

– Phil
Nov 20 '18 at 1:13

Thanks for commenting. Not passing that field means: { 'title': 'ComputingandInformationsystems', 'id': 1, 'children': 'true' } In the above JSON, two cases: Case 1: Not passing: { 'id': 1, 'children': 'true' } Case 2: Passing null { 'title': null, 'id': 1, 'children': 'true' }

– Yash Bansal
Nov 20 '18 at 1:21

@Phil: I need to know them, as both the scenarios are different and I need to handle them differently

– Yash Bansal
Nov 20 '18 at 1:28

add a comment |

2 Answers
2

active

oldest

votes

use default value in your classes. When the field not pass in json string the value will be the default. example code like below.

public class User {

    private String name;

    private String age="not set";



    public String getAge() {

        return age;

    }



    public void setAge(String age) {

        this.age = age;

    }



    public String getName() {

        return name;

    }



    public void setName(String name) {

        this.name = name;

    }



    @Override

    public String toString() {

        return "User{" +

                "name='" + name + ''' +

                ", age=" + age +

                '}';

    }

}



public class GsonClient {

    public static void main(String args) {

        String usersJson = "[ { "name": "henry" }, { "name": "justin","age":null } ]";

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

        User usersWithAge = gson.fromJson(usersJson, User.class);

        for (User user : usersWithAge) {

            System.out.println(user);

        }

    }

}

output is here

User{name='henry', age=not set}

User{name='justin', age=null}

answered Nov 20 '18 at 1:40

xxy

445311

Ohh! How can I forget this... Thanks

– Yash Bansal
Nov 20 '18 at 23:25

If this method can solve your problem, please mark it as "accepted" to help more people.

– xxy
Nov 21 '18 at 1:49

add a comment |

Object.keys(theObject) will contain the key if the value is set to null or undefined. Also theObject.hasOwnProperty(...) will let you know.

So convert the JSON to an object and inspect the keys to see if the value was marshalled as undefined, null, or not present.

answered Nov 20 '18 at 1:41

Steven Spungin

6,71832331

add a comment |

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2 Answers
2

active

oldest

votes

2 Answers
2

active

oldest

votes

use default value in your classes. When the field not pass in json string the value will be the default. example code like below.

public class User {

    private String name;

    private String age="not set";



    public String getAge() {

        return age;

    }



    public void setAge(String age) {

        this.age = age;

    }



    public String getName() {

        return name;

    }



    public void setName(String name) {

        this.name = name;

    }



    @Override

    public String toString() {

        return "User{" +

                "name='" + name + ''' +

                ", age=" + age +

                '}';

    }

}



public class GsonClient {

    public static void main(String args) {

        String usersJson = "[ { "name": "henry" }, { "name": "justin","age":null } ]";

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

        User usersWithAge = gson.fromJson(usersJson, User.class);

        for (User user : usersWithAge) {

            System.out.println(user);

        }

    }

}

output is here

User{name='henry', age=not set}

User{name='justin', age=null}

answered Nov 20 '18 at 1:40

xxy

445311

Ohh! How can I forget this... Thanks

– Yash Bansal
Nov 20 '18 at 23:25

If this method can solve your problem, please mark it as "accepted" to help more people.

– xxy
Nov 21 '18 at 1:49

add a comment |

use default value in your classes. When the field not pass in json string the value will be the default. example code like below.

public class User {

    private String name;

    private String age="not set";



    public String getAge() {

        return age;

    }



    public void setAge(String age) {

        this.age = age;

    }



    public String getName() {

        return name;

    }



    public void setName(String name) {

        this.name = name;

    }



    @Override

    public String toString() {

        return "User{" +

                "name='" + name + ''' +

                ", age=" + age +

                '}';

    }

}



public class GsonClient {

    public static void main(String args) {

        String usersJson = "[ { "name": "henry" }, { "name": "justin","age":null } ]";

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

        User usersWithAge = gson.fromJson(usersJson, User.class);

        for (User user : usersWithAge) {

            System.out.println(user);

        }

    }

}

output is here

User{name='henry', age=not set}

User{name='justin', age=null}

answered Nov 20 '18 at 1:40

xxy

445311

Ohh! How can I forget this... Thanks

– Yash Bansal
Nov 20 '18 at 23:25

If this method can solve your problem, please mark it as "accepted" to help more people.

– xxy
Nov 21 '18 at 1:49

add a comment |

use default value in your classes. When the field not pass in json string the value will be the default. example code like below.

public class User {

    private String name;

    private String age="not set";



    public String getAge() {

        return age;

    }



    public void setAge(String age) {

        this.age = age;

    }



    public String getName() {

        return name;

    }



    public void setName(String name) {

        this.name = name;

    }



    @Override

    public String toString() {

        return "User{" +

                "name='" + name + ''' +

                ", age=" + age +

                '}';

    }

}



public class GsonClient {

    public static void main(String args) {

        String usersJson = "[ { "name": "henry" }, { "name": "justin","age":null } ]";

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

        User usersWithAge = gson.fromJson(usersJson, User.class);

        for (User user : usersWithAge) {

            System.out.println(user);

        }

    }

}

output is here

User{name='henry', age=not set}

User{name='justin', age=null}

answered Nov 20 '18 at 1:40

xxy

445311

use default value in your classes. When the field not pass in json string the value will be the default. example code like below.

public class User {

    private String name;

    private String age="not set";



    public String getAge() {

        return age;

    }



    public void setAge(String age) {

        this.age = age;

    }



    public String getName() {

        return name;

    }



    public void setName(String name) {

        this.name = name;

    }



    @Override

    public String toString() {

        return "User{" +

                "name='" + name + ''' +

                ", age=" + age +

                '}';

    }

}



public class GsonClient {

    public static void main(String args) {

        String usersJson = "[ { "name": "henry" }, { "name": "justin","age":null } ]";

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

        User usersWithAge = gson.fromJson(usersJson, User.class);

        for (User user : usersWithAge) {

            System.out.println(user);

        }

    }

}

output is here

User{name='henry', age=not set}

User{name='justin', age=null}

answered Nov 20 '18 at 1:40

xxy

445311

answered Nov 20 '18 at 1:40

xxy

445311

answered Nov 20 '18 at 1:40

xxy

445311

answered Nov 20 '18 at 1:40

xxy

445311

Ohh! How can I forget this... Thanks

– Yash Bansal
Nov 20 '18 at 23:25

If this method can solve your problem, please mark it as "accepted" to help more people.

– xxy
Nov 21 '18 at 1:49

add a comment |

Ohh! How can I forget this... Thanks

– Yash Bansal
Nov 20 '18 at 23:25

If this method can solve your problem, please mark it as "accepted" to help more people.

– xxy
Nov 21 '18 at 1:49

Ohh! How can I forget this... Thanks

– Yash Bansal
Nov 20 '18 at 23:25

If this method can solve your problem, please mark it as "accepted" to help more people.

– xxy
Nov 21 '18 at 1:49

add a comment |

Object.keys(theObject) will contain the key if the value is set to null or undefined. Also theObject.hasOwnProperty(...) will let you know.

So convert the JSON to an object and inspect the keys to see if the value was marshalled as undefined, null, or not present.

answered Nov 20 '18 at 1:41

Steven Spungin

6,71832331

add a comment |

Object.keys(theObject) will contain the key if the value is set to null or undefined. Also theObject.hasOwnProperty(...) will let you know.

So convert the JSON to an object and inspect the keys to see if the value was marshalled as undefined, null, or not present.

answered Nov 20 '18 at 1:41

Steven Spungin

6,71832331

add a comment |

Object.keys(theObject) will contain the key if the value is set to null or undefined. Also theObject.hasOwnProperty(...) will let you know.

So convert the JSON to an object and inspect the keys to see if the value was marshalled as undefined, null, or not present.

answered Nov 20 '18 at 1:41

Steven Spungin

6,71832331

Object.keys(theObject) will contain the key if the value is set to null or undefined. Also theObject.hasOwnProperty(...) will let you know.

So convert the JSON to an object and inspect the keys to see if the value was marshalled as undefined, null, or not present.

answered Nov 20 '18 at 1:41

Steven Spungin

6,71832331

answered Nov 20 '18 at 1:41

Steven Spungin

6,71832331

answered Nov 20 '18 at 1:41

Steven Spungin

6,71832331

answered Nov 20 '18 at 1:41

Steven Spungin

6,71832331

add a comment |

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