receiving json and deserializing as List of object at spring mvc controller - spring

Question

My code is as below:
controller
#RequestMapping(value="/setTest", method=RequestMethod.POST, consumes="application/json")
public #ResponseBody ModelMap setTest(#RequestBody List<TestS> refunds, ModelMap map) {
for(TestS r : refunds) {
System.out.println(r.getName());
}
// other codes
}
TestS pojo
public class TestS implements Serializable {
private String name;
private String age;
//getter setter
}
Json request
var z = '[{"name":"1","age":"2"},{"name":"1","age":"3"}]';
$.ajax({
url: "/setTest",
data: z,
type: "POST",
dataType:"json",
contentType:'application/json'
});
It's giving this error
java.lang.ClassCastException: java.util.LinkedHashMap cannot be cast to com.air.cidb.entities.TestS
I am using spring 3.1.2 and jackson 2.0.4
Edit: I want to receive list of TestS objects at my controller method, and process them. I am not able to find if I am sending wrong json or my method signature is wrong.

Answer 1

Here is the code that works for me. The key is that you need a wrapper class.
public class Person {
private String name;
private Integer age;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
#Override
public String toString() {
return "Person [name=" + name + ", age=" + age + "]";
}
A PersonWrapper class
public class PersonWrapper {
private List<Person> persons;
/**
* #return the persons
*/
public List<Person> getPersons() {
return persons;
}
/**
* #param persons the persons to set
*/
public void setPersons(List<Person> persons) {
this.persons = persons;
}
}
My Controller methods
#RequestMapping(value="person", method=RequestMethod.POST,consumes="application/json",produces="application/json")
#ResponseBody
public List<String> savePerson(#RequestBody PersonWrapper wrapper) {
List<String> response = new ArrayList<String>();
for (Person person: wrapper.getPersons()){
personService.save(person);
response.add("Saved person: " + person.toString());
}
return response;
}
The request sent is json in POST
{"persons":[{"name":"shail1","age":"2"},{"name":"shail2","age":"3"}]}
And the response is
["Saved person: Person [name=shail1, age=2]","Saved person: Person [name=shail2, age=3]"]

Answer 2

This is not possible the way you are trying it. The Jackson unmarshalling works on the compiled java code after type erasure. So your
public #ResponseBody ModelMap setTest(#RequestBody List<TestS> refunds, ModelMap map)
is really only
public #ResponseBody ModelMap setTest(#RequestBody List refunds, ModelMap map)
(no generics in the list arg).
The default type Jackson creates when unmarshalling a List is a LinkedHashMap.
As mentioned by #Saint you can circumvent this by creating your own type for the list like so:
class TestSList extends ArrayList<TestS> { }
and then modifying your controller signature to
public #ResponseBody ModelMap setTest(#RequestBody TestSList refunds, ModelMap map) {

Answer 3

#RequestMapping(
value="person",
method=RequestMethod.POST,
consumes="application/json",
produces="application/json")
#ResponseBody
public List<String> savePerson(#RequestBody Person[] personArray) {
List<String> response = new ArrayList<String>();
for (Person person: personArray) {
personService.save(person);
response.add("Saved person: " + person.toString());
}
return response;
}
We can use Array as shown above.

Answer 4

Solution works very well,
public List<String> savePerson(#RequestBody Person[] personArray)
For this signature you can pass Person array from postman like
[
{
"empId": "10001",
"tier": "Single",
"someting": 6,
"anything": 0,
"frequency": "Quaterly"
}, {
"empId": "10001",
"tier": "Single",
"someting": 6,
"anything": 0,
"frequency": "Quaterly"
}
]
Don't forget to add consumes tag:
#RequestMapping(value = "/getEmployeeList", method = RequestMethod.POST, consumes="application/json", produces = "application/json")
public List<Employee> getEmployeeDataList(#RequestBody Employee[] employeearray) { ... }

Answer 5

I believe this will solve the issue
var z = '[{"name":"1","age":"2"},{"name":"1","age":"3"}]';
z = JSON.stringify(JSON.parse(z));
$.ajax({
url: "/setTest",
data: z,
type: "POST",
dataType:"json",
contentType:'application/json'
});

Answer 6

For me below code worked, first sending json string with proper headers
$.ajax({
type: "POST",
url : 'save',
data : JSON.stringify(valObject),
contentType:"application/json; charset=utf-8",
dataType:"json",
success : function(resp){
console.log(resp);
},
error : function(resp){
console.log(resp);
}
});
And then on Spring side -
#RequestMapping(value = "/save",
method = RequestMethod.POST,
consumes="application/json")
public #ResponseBody String save(#RequestBody ArrayList<KeyValue> keyValList) {
//Saving call goes here
return "";
}
Here KeyValue is simple pojo that corresponds to your JSON structure also you can add produces as you wish, I am simply returning string.
My json object is like this -
[{"storedKey":"vc","storedValue":"1","clientId":"1","locationId":"1"},
{"storedKey":"vr","storedValue":"","clientId":"1","locationId":"1"}]