Spring-MVC CRUD项目静态方法错误

问题描述

我正在研究MVC CRUD教程。我创建了控制器服务和主要方法。但是我的称为非静态方法的IDE不能被位于StudentController类addStudent和getStudent方法中的静态方法错误引用。谁能帮助我。也很乐意接受结构性建议。感谢您的帮助。

StudentController：

package com.example.demo;

import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.*;

import java.util.List;


@RestController

public class StudentController {
    StudentService studentService = new StudentService();

    @RequestMapping(value = "/students ",method = RequestMethod.GET,headers = "Accept=application/json")
    public List<Student> getStudent() {
        List<Student> studentList = studentService.getAllStudents();
        return studentList;
    }

    @RequestMapping(value = "/students ",headers = "Accept=application/json")
    public Student getStudentById(@PathVariable int id) {
        return StudentService.getStudent(id);
    }

    @RequestMapping(value = "/students ",headers = "Accept=application/json")
    public Student addStudent(@RequestBody Student student) {
        return StudentService.addStudent(student);
    }

    @RequestMapping(value = "/students",method = RequestMethod.PUT,headers = "Accept=application/json")
    public Student updateStudent(@RequestBody Student student) {
        return studentService.updateStudent(student);
    }

    @RequestMapping(value = "/student/{id}",method = RequestMethod.DELETE,headers = "Accept=application/json")
    public void deleteStudent(@PathVariable("id") int id) {
        studentService.deleteStudent(id);
    }


}



}

我的StudentService类：

package com.example.demo;

import javax.persistence.Id;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;


public class StudentService {

    private static HashMap<Integer,Student> studentHashMap = getStudentHashMap();


    public StudentService() {
        super();
        if (studentHashMap == null) {

            studentHashMap = new HashMap<Integer,Student>();

            Student student1 = new Student(1,"Erdem","Akıncı","Yazılım geliştirici");
            Student student2 = new Student(2,"Atıf","İmal","beden İşçisi");
            Student student3 = new Student(3,"Salih","Özdemir","Kasiyer");
            Student student4 = new Student(4,"Mustafa","Şensoy","Yazılım geliştirici");

            studentHashMap.put(1,student1);
            studentHashMap.put(2,student2);
            studentHashMap.put(3,student3);
            studentHashMap.put(4,student4);


        }

    }

    public static int getMaximumId() {
        int max = 0;
        for (int id : studentHashMap.keySet()) {
            if (max <= id) {
                max = id;
            }
        }
        return max;
    }

    public HashMap<Integer,Student> getStudentHashMap() {
        return studentHashMap;
    }

    public List<Student> getAllStudents() {
        List<Student> students = new ArrayList<Student>(studentHashMap.values());
        return students;
    }

    public Student getStudent(int id) {
        Student student = studentHashMap.get(id);
        return student;
    }

    public Student addStudent(Student student) {
        student.setId(getMaximumId() + 1);
        getStudentHashMap().put(student.getId(),student);
        return student;
    }

    public Student updateStudent(Student student) {
        if (student.getId() <= 0)
            return null;
        studentHashMap.put(student.getId(),student);
        return student;
    }

    public void deleteStudent(int id) {
        studentHashMap.remove(id);
    }

}

解决方法

正如IDE已经告诉您的那样，您不能从非静态上下文访问静态方法。这样做是因为在服务类中有一个静态方法，该方法在一种实例方法中使用。从方法getMaximumId中删除static关键字，这是不必要的。

否则，我会推荐一个初学者教程，您可以在其中了解有关Spring Annotation（服务，控制器，存储库）和依赖项注入概念的更多信息。

类似这样的内容：https://spring.io/guides/tutorials/rest/