spring JPA CRUD Repository and updating a record

问题

This is a question about a Spring Boot MVC application with Hibernate and PostgreSQL.

I have a web page that allows a user to set administrative / configuration data for an application, and I want to store this data in a single database record. I have a POJO to contain the data. I have coded up a Spring MVC app that persists this data.

The trouble is that each time the user saves the data (by doing a POST from the web page) the Spring application creates a new record in the database.

I'm using a Repository, and I was under the impression that each time I did a Repository.save() on the object it would update the existing record if there is one, otherwise create a new one and that it would identify the record based upon the primary key. I could not find an "update" method.

I have tried several ways around this issue but they either still make extra records, fail with a duplicate key error or just plain don't work.

Also, it seems that each time I start the web page or the application all the data in the database is removed.

So what's the trick? Thanks very much...

Here is my code:

AdminFormController.java

import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.beans.factory.annotation.Autowired;


@Controller
public class Admin_FormController 
{

    @Autowired
    private AdminDataRepository rep;

    @RequestMapping(value="/admin", method=RequestMethod.GET)
    public String adminForm(Model model) 
    {
        AdminData ad = new AdminData();
        model.addAttribute("adminForm", ad);

        ad = rep.findById(1L);

        if(ad != null)
            ad.setId(1L);

        return "adminForm";
    }

    @RequestMapping(value="/admin", method=RequestMethod.POST)
    public String adminSubmit(@ModelAttribute AdminData ad, Model model) 
    {

        // ad.setId(1L);;

        rep.save(ad);

        model.addAttribute("adminForm", ad);

        return "adminForm";
    }
}

AdminDataRepository.java

import org.springframework.data.repository.CrudRepository;

public interface AdminDataRepository extends CrudRepository<AdminData, String> 
{
    AdminData findById(Long Id);
}

AdminData.java

import java.util.logging.Logger;
import javax.persistence.*;

@Entity
public class AdminData 
{
    @Id
    @GeneratedValue(strategy=GenerationType.IDENTITY)   
    private Long id;

    private String useDates;

    private String startDate;
    private String endDate;

    public String getUseDates()
    {
        return useDates;
    }


    public String getStartDate() 
    {
        return startDate;
    }

    public String getEndDate() 
    {
        return endDate;
    }

    public void setUseDates(String s)
    {
        Logger.getGlobal().info(() -> "UseDates: " + s);
        useDates = s;
    }

    public void setStartDate(String s) 
    {
        Logger.getGlobal().info(() -> "Start Date: " + s);
        startDate = s;
    }

    public void setEndDate(String s) 
    {
        Logger.getGlobal().info(() -> "End Date: " + s);
        endDate = s;
    }

}

回答1:

You need to store the object somewhere between requests. Your options:

Using hidden form fields
Re-read it from the database (in your POST method)
Use session

1 is inconvenient, and not secure. 2 Doesn't support concurrency control. 3 is secure and correct.

To implement #3, add @SessionAttributes("yourAttributeName") just before your controller. Add a SessionStatus parameter to your POST method, and call sessionStatus.setComplete() when you're done with it.

Example here.

来源：https://stackoverflow.com/questions/31438523/spring-jpa-crud-repository-and-updating-a-record

标签

Spring

hibernate

spring-mvc

jpa