Angular 2 - resolving the access control allow origin header issue

Question

Angular 2 - resolving the access control allow origin header issue

My project utilizes Spring on the back-end and Angular2 on the front-end. In the webapp folder of my Spring project, there is a JSON file that I am attempting to access from Angular.

I can successfully access the file by directly typing "http://localhost:8080/project1/test.json"

However, when trying to access the same link from Angular, I encounter an error message stating "no access control allow origin header"

Here is a snippet of my Angular code: 1. Function getJson() defined in service.ts:

getJson(){
    return this.http.get('http://localhost:8080/project1/test.json')
    .map((response:Response) => response.json());
}

Calling getJson():

results=[];

this._manoService.getJson().subscribe(resJsonData => this.results = resJsonData);

I have created proxy.conf.json with the following configuration:

{
 "/project1": {
 "target": "http://localhost:8080",
 "secure": false
   } 
}

In addition, I have added "start": "ng serve --proxy-config proxy.conf.json", to package.json

Despite these changes, I continue to face the same issue. Am I missing something here?

java spring angular typescript

Answer 1

Answer №1

Web browsers enforce a same origin policy for security purposes. If your Angular page is hosted on a different origin, such as localhost:3000 instead of localhost:8080, the browser will block access.

The same origin policy is crucial in ensuring that sensitive information, like your bank account details, remains secure when you visit other websites.

To enable cross-origin access, there are various methods available. One simple approach is to host both your Angular application and service on the same domain and port in production. During development, you can configure ng serve to act as a proxy server, forwarding requests from localhost:3000 to localhost:8080. Detailed instructions can be found in the Angular proxy documentation.

If you require cross-origin requests even in production, Spring offers an easy way to allow it by using the @CrossOrigin annotation in your service methods. This may impact cookie-based authentication, so exploring alternatives like oauth is recommended. Adding the @CrossOrigin annotation will prompt Spring-REST to include the Access-Control-Allow-Origin http-header.

An alternative to proper CORS implementation is JSONP, but this method is considered outdated and should be avoided. JSONP works by utilizing the ability to include a <script> tag from any origin, allowing the server to return JavaScript code that invokes a specified callback function with relevant data.

Answer 2

Web browsers enforce a same origin policy for security purposes. If your Angular page is hosted on a different origin, such as localhost:3000 instead of localhost:8080, the browser will block access.

The same origin policy is crucial in ensuring that sensitive information, like your bank account details, remains secure when you visit other websites.

To enable cross-origin access, there are various methods available. One simple approach is to host both your Angular application and service on the same domain and port in production. During development, you can configure ng serve to act as a proxy server, forwarding requests from localhost:3000 to localhost:8080. Detailed instructions can be found in the Angular proxy documentation.

If you require cross-origin requests even in production, Spring offers an easy way to allow it by using the @CrossOrigin annotation in your service methods. This may impact cookie-based authentication, so exploring alternatives like oauth is recommended. Adding the @CrossOrigin annotation will prompt Spring-REST to include the Access-Control-Allow-Origin http-header.

An alternative to proper CORS implementation is JSONP, but this method is considered outdated and should be avoided. JSONP works by utilizing the ability to include a <script> tag from any origin, allowing the server to return JavaScript code that invokes a specified callback function with relevant data.

Answer 3

Answer №2

Suppose you have a Spring @RestController service that needs to be accessed from a website outside of the server it's running on. In this case, simply add a @CrossOrigin annotation to the handler method.

For instance, in the following example, the @CrossOrigin is only enabled for the addSite handler method.

@RestController
public class SiteController {

    @Autowired
    private SiteServiceImpl siteService;

    @CrossOrigin(origins = "*")
    @RequestMapping(method = RequestMethod.POST, value = "/api/sites")
    public void addSite(@RequestBody Site site){
        siteService.addSite(site);
    }

You can also enable @CrossOrigin for the entire controller by adding it at the @RestController level.

For example:

@RestController
@CrossOrigin(origins = "*")
public class SiteController {

    @Autowired
    private SiteServiceImpl siteService;


    @RequestMapping(method = RequestMethod.POST, value = "/api/sites")
    public void addSite(@RequestBody Site site){
        siteService.addSite(site);
    }

The @CrossOrigin(origins = "*") annotation allows resources external to the rest service to consume it. If the service should only be accessible from specific origins, update the origins value to the server name where those resources are located, e.g.,

@CrossOrigin(origins = "http://myothersite.com")

Additional information on this topic can be found on the Spring website: cors-support-in-spring-framework

Answer 4

Suppose you have a Spring @RestController service that needs to be accessed from a website outside of the server it's running on. In this case, simply add a @CrossOrigin annotation to the handler method.

For instance, in the following example, the @CrossOrigin is only enabled for the addSite handler method.

@RestController
public class SiteController {

    @Autowired
    private SiteServiceImpl siteService;

    @CrossOrigin(origins = "*")
    @RequestMapping(method = RequestMethod.POST, value = "/api/sites")
    public void addSite(@RequestBody Site site){
        siteService.addSite(site);
    }

You can also enable @CrossOrigin for the entire controller by adding it at the @RestController level.

For example:

@RestController
@CrossOrigin(origins = "*")
public class SiteController {

    @Autowired
    private SiteServiceImpl siteService;


    @RequestMapping(method = RequestMethod.POST, value = "/api/sites")
    public void addSite(@RequestBody Site site){
        siteService.addSite(site);
    }

The @CrossOrigin(origins = "*") annotation allows resources external to the rest service to consume it. If the service should only be accessible from specific origins, update the origins value to the server name where those resources are located, e.g.,

@CrossOrigin(origins = "http://myothersite.com")

Additional information on this topic can be found on the Spring website: cors-support-in-spring-framework

Angular 2 - resolving the access control allow origin header issue

Answer №1

Answer №2

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