Tips for Spring Boot implementation and solving cross-domain problems

With the popularity of front-end and back-end separation, cross-domain issues between front-end and back-end have gradually become a problem faced by web developers. Cross-domain issues involve the browser's same-origin policy, that is, by default, the browser only allows pages to initiate requests to servers of the same origin, but not to servers with other domain names. This article will introduce how to use the Spring Boot framework to implement and solve cross-domain problems.

1. What is a cross-domain problem?

Cross-domain problem means that in the browser, when a web application running under domain name A sends a request to the web application under domain name B, the browser will block the request because this Does not comply with the browser's same-origin policy. The same-origin policy means that the browser only allows pages to initiate requests to the server if they have the same protocol, domain name, and port number.

2. Spring Boot supports cross-domain methods for solving cross-domain problems

Spring Boot provides a variety of methods for solving cross-domain problems. Here are some common methods.

2.1 Use the annotation @CrossOrigin

In Spring Boot, you can use the annotation @CrossOrigin to implement cross-domain requests. The @CrossOrigin annotation can be used at the class or method level, and can specify some options for CORS, such as domain names allowed for cross-domain access, allowed request methods, etc. The following is a sample code using the @CrossOrigin annotation:

@RestController
@RequestMapping("/api")
@CrossOrigin(origins = "http://localhost:8080", maxAge = 3600)
public class ApiController {

    @GetMapping("/hello")
    public String hello() {
        return "Hello World!";
    }
}

In the above code, the @CrossOrigin annotation is used and the cross-domain domain name is specified as http://localhost:8080, and the maximum cache time is set as 1 hour. In this way, when making a front-end Ajax request, you can access http://localhost:8080 across domains. It should be noted that the @CrossOrigin annotation should be added to the controller class or method, not to the @RequestBody parameter.

2.2 Configuring WebMvcConfigurer

Another way to solve the cross-domain problem is to implement the WebMvcConfigurer interface, override the addCorsMappings method, and use CorsRegistry to configure domain names that allow cross-domain access. The following is a sample code:

@Configuration
public class CorsConfig implements WebMvcConfigurer {

    @Override
    public void addCorsMappings(CorsRegistry registry) {
        registry.addMapping("/api/**")
                .allowedOrigins("http://localhost:8080")
                .allowedMethods("GET", "POST")
                .maxAge(3600);
    }
}

In the above code, the CorsConfig class implements the WebMvcConfigurer interface and covers the addCorsMappings method, allowing only GET and POST request access under the http://localhost:8080 domain name. Paths containing "/api" will be subject to CORS restrictions, while other paths will not have any restrictions.

2.3 Configuring Filter

Using filters is also a way to solve cross-domain problems. The following is an example of using filters:

@Component
public class CorsFilter implements Filter {

    @Override
    public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain)
            throws ServletException, IOException {
        HttpServletResponse response = (HttpServletResponse) res;
        response.setHeader("Access-Control-Allow-Origin", "http://localhost:8080");
        response.setHeader("Access-Control-Allow-Methods", "GET, POST");
        response.setHeader("Access-Control-Max-Age", "3600");
        chain.doFilter(req, res);
    }
}

In the above code, the CorsFilter class implements the Filter interface and adds Access-Control-Allow-Origin, Access-Control-Allow-Methods, Access-Control- Request header information such as Max-Age allows access to GET and POST requests under the http://localhost:8080 domain name.

3. Summary

This article introduces three common methods of using the Spring Boot framework to implement and solve cross-domain problems. CORS restrictions and controls can be achieved by using the annotation @CrossOrigin, configuring WebMvcConfigurer, and using filters. In actual development, you should choose the most suitable method to solve cross-domain problems according to your own needs.

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