Angular HttpErrorResponse GET 请求

Posted 2023-03-31

【中文标题】Angular HttpErrorResponse GET 请求

【英文标题】：Angular HttpErrorResponse GET Request

【发布时间】：2021-11-24 00:14:07

【问题描述】：

我有一个简单的 Quarkus 项目，想用 HttpClient 在 Angular 表中显示数据。我也有一个 CORS 过滤器。无论如何，我收到以下错误： Angular table with no date, HttpErrorResponse Status 0

service.ts

import  HttpClient  from '@angular/common/http';
import  Injectable  from '@angular/core';
import  Observable  from 'rxjs';
import  School  from './model/school';

@Injectable(
  providedIn: 'root'
)
export class SchoolService 

  url = "localhost:8080/school"

  constructor(public http: HttpClient)  

  getAll(): Observable<School[]> 
    return this.http.get<School[]>(this.url);
  

  getById(id: number): Observable<School> 
    const url = "locahlost:8080/school/id";
    return this.http.get<School>(url);
  

组件的ts

import  Component, OnInit  from '@angular/core';
import  School  from '../model/school';
import  SchoolService  from '../school.service';

@Component(
  selector: 'app-dashboard',
  templateUrl: './dashboard.component.html',
  styleUrls: ['./dashboard.component.css']
)
export class DashboardComponent implements OnInit 

  schools: School[] = [];
  
  constructor(public schoolService: SchoolService)  

  ngOnInit(): void 
    this.schoolService.getAll().subscribe(e => 
      this.schools = e;
    );
  

html

<table>
    <thead>
        <tr>
            <th>ID</th>
            <th>Name</th>
            <th>Street</th>
        </tr>
    </thead>
    <tbody>
        <tr *ngFor="let school of schools">
            <td>school.id</td>
            <td>school.name</td>
            <td>school.street</td>
        </tr>
    </tbody>
</table>

服务器模型

package model;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;

@Entity
public class School 

    @Id
    @GeneratedValue
    private int id;
    private String name;
    private String street;

    public int getId() 
        return id;
    

    public void setId(int id) 
        this.id = id;
    

    public String getName() 
        return name;
    

    public void setName(String name) 
        this.name = name;
    

    public String getStreet() 
        return street;
    

    public void setStreet(String street) 
        this.street = street;
    

资源

package rest;

import model.School;

import javax.inject.Inject;
import javax.transaction.Transactional;
import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.PathParam;
import javax.ws.rs.Produces;
import javax.ws.rs.core.MediaType;
import java.util.List;

@Path("school")
@Produces(MediaType.APPLICATION_JSON)
@Transactional
public class SchoolResource 

    @Inject
    SchoolDao dao;

    @GET
    public List<School> getAll() 
        return dao.getAll();
    

    @Path("id")
    @GET
    public School getById(@PathParam("id") int id) 
        return dao.getById(id);
    

道

package rest;

import model.School;

import javax.enterprise.context.Dependent;
import javax.inject.Inject;
import javax.persistence.EntityManager;
import java.util.List;

@Dependent
public class SchoolDao 

    @Inject
    EntityManager em;

    public List<School> getAll() 
        return em.createQuery("select s from School s", School.class).getResultList();
    

    public School getById(int id) 
        return em.find(School.class, id);
    

提前谢谢你，我认为问题一定出在服务器上，因为我已经尝试使用 JSON 文件而不是 Quarkus 数据显示数据，它确实有效。

【问题讨论】：

也许你的url前面应该有一个http://，或者https://？控制台有错误吗？

【参考方案1】：

正如@R.Richards提到的in a comment，在服务文件的url前面加上“http://”解决了这个问题。