Thymeleaf表单将除一个输入外的所有输入传递给Java控制器

Question

My thymeleaf form has three inputs, when I submit it my controller is receiving the second and the third, but not the first one (first input is null)

I have similar forms and method to add records to a MySQL database which work with no problems. I have diplayed the two first inputs in my controller, first (Id of the entity) is null, second is well informed

Here is my form: addDepartment.html

<br/>
<form th:action="@{/university/addDepartment}"
     th:object="${department}" method="POST">
     Department Name
     <input type="text" th:field="*{deptName}" />    
     <br/>
     Department building
     <input type="text" th:field="*{building}" />    
     <br/>
     Budget
     <input type="number" th:field="*{budget}" th:value=0/>    
     <br/>
     <input type="submit" value="Add" />
  </form>

  <!-- Check if errorMessage is not null and not empty -->

  <div th:if="${errorMessage}" th:utext="${errorMessage}"
     style="color:red;font-style:italic;">
     ...
  </div>

And my controller

    // ADD a department to the database
    // Show the addDepartment page
   @RequestMapping(value= { "university/addDepartment" }, method = RequestMethod.GET)
     public String showAddDepartment(Model model) {

         Department department = new Department();
         model.addAttribute("department", department); 
         return "addDepartment";
     }

     // Add the department to the database
     @RequestMapping(value = { "university/addDepartment" }, method = RequestMethod.POST)
        public String saveDepartment(Model model, //
                @ModelAttribute("department") 
                @Validated Department department) {

            System.out.println("DEPARTMENT: " + department.toString());
            String deptName = department.getDeptName();
            System.out.println("DEPARTMENT NAME: " + deptName); 
            String building = department.getBuilding();  
            System.out.println("BUILDING: " + building); 
            int budget = department.getBudget(); 

            if (deptName != null && deptName.length() > 0 //
                    && building != null && building.length() > 0 //
                    && budget >= 0) {
                Department newDepartment = new Department(deptName, building, budget);
                departmentrepo.save(newDepartment);

                return "redirect:/university/departmentList";
            }

            Object errorMessage = "All fields are mantatory";
            model.addAttribute("errorMessage", errorMessage );              
            return "addDepartment";
        }

Here is the Department class:

    @Entity
    @Table(name="department") // This annotation is needed only if the 
    table has a different name to this class
    @EntityListeners(AuditingEntityListener.class)
    public class Department {

@Id
private String deptName;

private String building;
private int budget; 

//Constructors
public Department() {       
}

public Department(String deptName, String building, int budget) {
    this.deptName = deptName;
    this.building = building;
    this.budget = budget;
}
    ...GETTERS and SETTERS 

The deptName is always null, but the other two inputs are ok

DEPARTMENT NAME: null BUILDING: Main

UPDATE: I think I found the solution, but if someone can explain the reason... I just passed the deptName in a @RequestParam annotation.

      @RequestMapping(value = { "university/addDepartment" }, method = 
      RequestMethod.POST)
        public String saveDepartment(Model model, //
                @ModelAttribute("department") Department department,
                @RequestParam("deptName")  String deptName) {

            //String deptName = department.getDeptName();
            System.out.println("DEPARTMENT NAME: " + deptName); 
            String building = department.getBuilding();  
            System.out.println("BUILDING: " + building); 
            int budget = department.getBudget(); 

            if (deptName != null && deptName.length() > 0 //
                    && building != null && building.length() > 0 //
                    && budget >= 0) {
                Department newDepartment = new Department(deptName, building, budget);
                departmentrepo.save(newDepartment);

                return "redirect:/university/departmentList";
            }

            Object errorMessage = "All fields are mantatory";
            model.addAttribute("errorMessage", errorMessage );              
            return "addDepartment";
        }x`

Answer 1

There are a few issues with this code, but the first thing to try is removing the @Id annotation from your deptName property. Create a Long (or Integer ) id property and annotate this instead. You can more simply call the department name property name too.

You will also want to make sure that you have the getters and setters done correctly, or more advisable - just use Project Lombok to get rid of extra text and potential for mistakes.

@Entity
@Table
@Data //see Project Lombok
public class Department {

   @Id
   private Long id;

   private String name;

   private String building;

   private int budget; //I'd consider making this more precise by using BigDecimal

}

For your controller, let's more simply try this to see whether it is still breaking.

@GetMapping("/university/addDepartment")
public String showAddDepartment(Model model) {

   model.addAttribute("department", new Department()); 
   return "addDepartment";
}

@PostMapping("/university/addDepartment")
public String saveDepartment(@ModelAttribute("department") Department department) {
    System.out.println("name="+department.getName()); //use a logger if you have one available
    return "addDepartment";
}

In your form, you only need the th: notation if you want Thymeleaf to evaluate the logic. So you can change th:value=0 to value=0 if you really intend this.