GET 请求返回 404 未找到

Question

我有一个 Spring Boot 应用程序，我只是发送一个 GET 请求以从预先填充的列表中获取一些数据。 该列表存在于控制器类中。当我点击 URL 时，我不断收到 404 错误。

Student.java

package com.SpringBootDemo.entities;

public class Student {

    private Integer studentId;
    private String studentName;

    public Student(Integer studentId, String studentName) {
        super();
        this.studentId = studentId;
        this.studentName = studentName;
    }
    public Integer getStudentId() {
        return studentId;
    }
    public void setStudentId(Integer studentId) {
        this.studentId = studentId;
    }
    public String getStudentName() {
        return studentName;
    }
    public void setStudentName(String studentName) {
        this.studentName = studentName;
    }


}

StudentController.java

package com.SpringBootDemo.controller;

import java.util.Arrays;
import java.util.List;

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import com.SpringBootDemo.entities.Student;

@RestController
@RequestMapping("api/v1/students")
public class StudentController {

    private static final List<Student> STUDENTS = Arrays.asList(
            new Student(1,"ABC"),
            new Student(2,"DEF"),
            new Student(3,"HIJ"));

    @GetMapping(path = "{studentId}")
    public Student getStudentById(@PathVariable("studentId")Integer studentId) 
    {
        System.out.println("inside the controller");
        return STUDENTS.stream()
                .filter(student -> studentId.equals(student.getStudentId()))
                .findFirst()
                .orElseThrow(()->new IllegalStateException("Student with id "+studentId+" doesn't exist"));

    }

}

Application.properties

spring.datasource.url=jdbc:mysql://localhost:3306/spring_project
spring.datasource.username=root
spring.datasource.password=Pblock@20
server.port = 8081
spring.jpa.show-sql=true

我的堆栈跟踪

020-06-01 15:07:29.879  INFO 21012 --- [           main] .s.d.r.c.RepositoryConfigurationDelegate : Finished Spring Data repository scanning in 10ms. Found 0 JPA repository interfaces.
2020-06-01 15:07:30.275  INFO 21012 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat initialized with port(s): 8081 (http)
2020-06-01 15:07:30.281  INFO 21012 --- [           main] o.apache.catalina.core.StandardService   : Starting service [Tomcat]
2020-06-01 15:07:30.281  INFO 21012 --- [           main] org.apache.catalina.core.StandardEngine  : Starting Servlet engine: [Apache Tomcat/9.0.35]

Answer 1

您的端点错误。将 @GetMapping(path = "{studentId}") 更改为 @GetMapping("/{studentId}")

@RestController
@RequestMapping("api/v1/students")
public class StudentController {

    private static final List<Student> STUDENTS = Arrays.asList(
            new Student(1,"ABC"),
            new Student(2,"DEF"),
            new Student(3,"HIJ"));

    @GetMapping("/{studentId}")
    public Student getStudentById(@PathVariable("studentId")Integer studentId) 
    {
        System.out.println("inside the controller");
        return STUDENTS.stream()
                .filter(student -> studentId.equals(student.getStudentId()))
                .findFirst()
                .orElseThrow(()->new IllegalStateException("Student with id "+studentId+" doesn't exist"));

    }

}

Answer 2

当我将 @ComponentScan(basePackageClasses=StudentController.class) 添加到我的基类时，它起作用了。

SpringSecurityDemoApplication

package com.SpringSecurityDemo;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.autoconfigure.security.servlet.SecurityAutoConfiguration;
import org.springframework.context.annotation.ComponentScan;

import com.SpringBootDemo.controller.StudentController;

@SpringBootApplication
@ComponentScan(basePackageClasses=StudentController.class)
public class SpringSecurityDemoApplication {

    public static void main(String[] args) {
        SpringApplication.run(SpringSecurityDemoApplication.class, args);
    }

}

Answer 3

由于您没有提供正确的网址，因此您点击的网址无法识别为获取。因此抛出 404 not found 状态。 将您的休息控制器的映射更改为 @GetMapping("/{studentId}") ，然后点击 url http://localhost:8081/api/v1/students/1