Nguyên nhân gây ra lỗi etat 400 spring mvc

To respond with an HTTP 400 error in a Spring MVC controller method that returns a String, you can throw a ResponseStatusException with a status of BAD_REQUEST.

Here is an example of how you can do this:

@ResponseBody  
@GetMapping("/some-url")  
public String someMethod() {  
    // some logic here  
    throw new ResponseStatusException(HttpStatus.BAD_REQUEST, "Invalid request");  
}

In this example, the ResponseStatusException is thrown with a status of BAD_REQUEST (HTTP 400) and a message. The message will be included in the response body.

Alternatively, you can use the HttpServletResponse object to set the response status and write the response body manually:

Good day. I faced a problem: I'm trying to send POST request with some attributes, but I get "Bad request" response.

Here is my controller:

@Controller
@RequestMapping("/group")
public class GroupController {
   private static org.apache.log4j.Logger logger = org.apache.log4j.Logger
     .getLogger(GroupController.class);
   @Autowired
   private GroupService                   groupService;
   @RequestMapping(value = "/add", method = RequestMethod.POST)
   public String addGroup(@ModelAttribute("group") final Group group) {
      GroupController.logger.info("I'm in POST method");
      this.groupService.addGroup(group);
      return "redirect:/student/add";
   }
}

Here is my entity:

@Entity
@Table(name = "university_groups")
public class Group implements Serializable {
   private static final long serialVersionUID = 1L;
   @OneToMany(fetch = FetchType.EAGER, cascade = CascadeType.ALL, mappedBy = "group")
   Set              students;
   @ManyToOne(fetch = FetchType.EAGER, cascade = CascadeType.ALL)
   @NotNull
   @JoinColumn(name = "department_id")
   private Department        department;
   @Id
   @Column(name = "group_name", unique = true, nullable = false)
   private String            group;
   public Group() {
   }
   public Group(final String group, final Department deparment) {
      this.group = group;
      this.department = deparment;
   }
   public Department getDepartment() {
      return this.department;
   }
   public String getGroup() {
      return this.group;
   }
   public Set getStudents() {
      return this.students;
   }
   public void setDepartment(final Department department) {
      this.department = department;
   }
   public void setGroup(final String group) {
      this.group = group;
   }
   public void setStudents(final Set students) {
      this.students = students;
   }
   @Override
   public String toString() {
      return this.group;
   }
}

Here is part of JSP page:

    

        

            

                    
                
            

        
        

            

                    
                
            

                    
                
            
">
        
        

            
" />
        
    

Here is Department entity:

@Entity
@Table(name = "departments")
public class Department implements Serializable {
   private static final long serialVersionUID = 1L;
   @Id
   @Column(name = "department", unique = true, nullable = false)
   private String            department;
   @ManyToOne(fetch = FetchType.EAGER, cascade = CascadeType.ALL)
   @NotNull
   @JoinColumn(name = "faculty_id")
   private Faculty           faculty;
   @OneToMany(fetch = FetchType.EAGER, cascade = CascadeType.ALL, mappedBy = "department")
   private Set        groups;
   @ManyToMany(fetch = FetchType.LAZY)
   @JoinTable(name = "users_departments", joinColumns = {@JoinColumn(name = "department_id", nullable = false, insertable = true, updatable = true) }, inverseJoinColumns = {@JoinColumn(name = "user_name", nullable = false, insertable = true, updatable = true) })
   private Set         users;
   public Department() {
   }
   public Department(final String department, final Faculty faculty) {
      this.department = department;
      this.faculty = faculty;
   }
   public String getDepartment() {
      return this.department;
   }
   public Faculty getFaculty() {
      return this.faculty;
   }
   public Set getGroups() {
      return this.groups;
   }
   public Set getUsers() {
      return this.users;
   }
   public void setDepartment(final String department) {
      this.department = department;
   }
   public void setFaculty(final Faculty faculty) {
      this.faculty = faculty;
   }
   public void setGroups(final Set groups) {
      this.groups = groups;
   }
   public void setUsers(final Set users) {
      this.users = users;
   }
   @Override
   public String toString() {
      return this.department;
   }
}

If I remove @ModelAttribute("group") final Group group from controller method, all is OK. Please, help me, I can't understand why it doesn't works.