Spring 3 MVC - Advanced Data Binding - Form Request with List of Simple Objects

Question

I've read through all of the Spring 3 Web docs: http://static.springsource.org/spring/docs/3.0.x/spring-framework-reference/html/spring-web.html but have been completely unable to find any interesting documentation on binding more complicated request data, for example, let's say I use jQuery to post to a controller like so:

$.ajax({
    url: 'controllerMethod',
    type: "POST",
    data : {
        people : [
        {
            name:"dave", 
            age:"15"
        } ,
{
            name:"pete", 
            age:"12"
        } ,
{
            name:"steve", 
            age:"24"
        } ]
    },
    success: function(data) {
        alert('done');
    }
});

How can I accept that through the controller? Preferably without having to create a custom object, I'd rather just be able to use simple data-types, however if I need custom objects to make things simpler, I'm fine with that too.

To get you started:

@RequestMapping("/controllerMethod", method=RequestMethod.POST)
public String doSomething() {
    System.out.println( wantToSeeListOfPeople );
}

Don't worry about the response for this question, all I care about is handling the request, I know how to deal with the responses.

EDIT:

I've got more sample code, but I can't get it to work, what am I missing here?

select javascript:

var person = new Object();
    person.name = "john smith";
    person.age = 27;

    var jsonPerson = JSON.stringify(person);

    $.ajax({
        url: "test/serialize",
        type : "POST",
        processData: false,
        contentType : 'application/json',
        data: jsonPerson,
        success: function(data) {
            alert('success with data : ' + data);
        },
        error : function(data) {
            alert('an error occurred : ' + data);
        }
    });

controller method:

public static class Person {

        public Person() {
        }

        public Person(String name, Integer age) {
            this.name = name;
            this.age = age;
        }
        String name;
        Integer age;

        public Integer getAge() {
            return age;
        }

        public void setAge(Integer age) {
            this.age = age;
        }

        public String getName() {
            return name;
        }

        public void setName(String name) {
            this.name = name;
        }
    }

    @RequestMapping(value = "/serialize")
        @ResponseBody
        public String doSerialize(@RequestBody Person body) {
            System.out.println("body : " + body);
            return body.toString();
        }

this renders the following exception:

org.springframework.web.HttpMediaTypeNotSupportedException: Content type 'application/json' not supported

If the doSerialize() method takes a String as opposed to a Person, the request is successful, but the String is empty

Answer 1

Your jQuery ajax call produces the following application/x-www-form-urlencoded request body (in %-decoded form):

people[0][name]=dave&people[0][age]=15&people[1][name]=pete&people[1][age]=12&people[2][name]=steve&people[2][age]=24

Spring MVC can bind properties indexed with numbers to Lists and properties indexed with strings to Maps. You need the custom object here because @RequestParam doesn't support complex types. So, you have:

public class People {
    private List<HashMap<String, String>> people;

    ... getters, setters ...
}

@RequestMapping("/controllerMethod", method=RequestMethod.POST)        
public String doSomething(People people) {        
    ...
} 

You can also serialize data into JSON before sending them and then use a @RequestBody, as Bozho suggests. You may find an example of this approach in the mvc-showcase sample.

Answer 2

if you have <mvc:annotation-driven> enabled then:

@RequestMapping("/controllerMethod", method=RequestMethod.POST)
public String doSomething(@RequestBody List<Person> people) {
    System.out.println( wantToSeeListOfPeople );
}

(List<Person> might not be the structure you would like to obtain, it's just an example here)

You can try setting the Content-Type of $.ajax to be application/json, if it doesn't work immediately.