与前端和后端(Java -Angular)的错误沟通

Question

我尝试与我的Java/Spring Boot后端传达我的角前端。但是终端向我展示了这个错误：

[hpm]试图从本地主机来代替/api/dados时发生错误：4500至http：/localhost：8080（econnrefused）（econnrefused）（https://nodejs.org/api/erpi/errors.html.html#errors.html#errors_common_common_system_system_semrors）P>

这是我的exmemple.service.ts（Angular）代码。在这里，我请求数据：

import {Injectable} from "@angular/core";
import {Http, Response} from "@angular/http";
import 'rxjs/Rx';
@Injectable()
export class ExService{
  constructor(private http: Http){
  }
  getName(){
    return this.http.get("/api/dados").map(
      (response: Response) =>{
        return response.json();
      }
    );
  }
}

这是我的exemple.java（Java代码）。它负责发送数据：

package com.lucas.bef.Envia;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
@RestController
@RequestMapping("/api/dados")
public class Dados {
    String teste;
    public Dados(){
        this.teste = "LUCAS";
    }
    public void setNome(String nome){
        this.teste = nome;
    }
    @GetMapping( value = {"","/"})
    public String getNome(){
        return teste;
    }
}

如果我启动了春季应用程序...终端向我显示一条消息，tomcat以8080端口开始。

i创建一个configuration proxy文件（proxy-conf.json）：

{
  "/api":{
    "target": "http:/localhost:8080",
    "secure": false
  }
}

请有人帮我。我需要这样做。非常重要。谢谢！

Answer 1

问题似乎与您一起运行两个应用程序（前端和后端）在不同的端口上。这样的请求称为CORS。您可以在Spring-Boot应用中启用CORS。或要临时测试，请下载此Chrome插件

Answer 2

首先，您已经设置了" target"：" http：/localhost：8080"，错误！是http：//localhost：8080

也请尝试重写如下服务的请求

 getName(){
    return this.http.get("http://localhost:8080/api/dados").map(
      (response: Response) =>{
        return response.json();
      }
    );
  }

检查它是否有效！您必须订阅服务方法的可观察响应

还必须允许Spring服务器与Angular应用程序进行通信。为此，您必须从后端配置COR

import java.io.IOException;
import javax.servlet.FilterChain;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.springframework.web.filter.GenericFilterBean;

public class CORSFilter extends GenericFilterBean {
  @Override
  public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain)
      throws IOException, ServletException {
    if (((HttpServletRequest) req).getMethod().equals("OPTIONS")) {
      HttpServletResponse response = (HttpServletResponse) res;
      response.setHeader("Access-Control-Allow-Origin", "http://localhost:4500");
      response.setHeader("Access-Control-Allow-Credentials", "true");
      response.setHeader("Access-Control-Allow-Methods", "GET,HEAD,OPTIONS,POST,PUT,DELETE");
      response.setHeader("Access-Control-Allow-Headers", "Access-Control-Allow-Headers, Origin,Accept, "
            + "X-Requested-With, Content-Type, Access-Control-Request-Method, Access-Control-Request-Headers");
    } else {
      chain.doFilter(req, res);
    }
  }
}