Spring MVC and AJAX error

Question

In JSP file I have field to enter student's group and then pass this data to entity class GroupStudent (without getter and setter methods)

@Entity
@Table(name = "GroupStudent")
@NamedQueries({ 
@NamedQuery(name = "GroupStudent.getAllGroups", // get all groups
            query = "select g from GroupStudent g"),
@NamedQuery(name = "GroupStudent.getGroupByName", // get group by name
            query = "select g from GroupStudent g where g.groupStudentNumber = :name")
})
public class GroupStudent implements Serializable {
public GroupStudent() {}

public GroupStudent(String groupStudentNumber) {
    this.groupStudentNumber = groupStudentNumber;
}
// table GroupStudent fields
private Long groupStudentId;
private String groupStudentNumber;
}

JSP

<label>Group</label>
<input id="groupStudentNumber"/>
<input type="submit" value="Add" onclick="addGroupAjax()" />

and ajax function to pass data to Spring Controller

function addGroupAjax() {
            var groupStudentNumber = $('#groupStudentNumber').val();

            $.ajax({
                type: "POST",
                url: "/IRSystem/addData.html",
                contentType: "application/json; charset=utf-8",
                dataType: "json",
                data: "{groupStudentNumber:" + groupStudentNumber + "}",
                success: function(response) {

                },
                error: function(e) {
                    alert("Error" + e);
                }
            });
        } 

but it do not pass data to controller. The field of the entity is empty.

@RequestMapping(value = "/addData.html", method = RequestMethod.POST)
public @ResponseBody Student addNewGroup(@ModelAttribute(value = "group") GroupStudent group) {

    System.out.println("Entered group: " + group.getGroupStudentNumber());

    return new Student();
}

and another thing that i can not pass entity Student to ajax too. I added to Spring jars

jackson-core-asl-1.7.1 and jackson-mapper-asl-1.7.1 to be able to pass entity object to ajax. But it gave not result. When i try to pass data (to ajax) in Google Chrome I have a window with error Error[object Object]. I do not know why it happens. I would appreciate any information, thank you.

Answer 1

Your controller is not properly set up to accept the post. If you are posting a JSON body, you need to use the @RequestBody annotation for your method parameter, like this:

@RequestMapping(value = "/addData.html", method = RequestMethod.POST)
public @ResponseBody Student addNewGroup(@RequestBody GroupStudent group) {
    System.out.println("Entered group: " + group.getGroupStudentNumber());
    return new Student();
}

This way, your JSON will be directly mapped to your GroupStudent object.

Answer 2

您还需要通过将消耗= MediaType.APPLICATION_JSON_VALUE添加到@RequestMapping中，产生= MediaType.APPLICATION_JSON_VALUE来指定消耗媒体类型。