Dynamicallly retrieve Spring Boot CORS Configuration from database for specific method in a Controller

Question

I am trying to set the CORS configuration at Controller level using

@CrossOrigin on Controller and Handler Method

public class AccountController {

@CrossOrigin("retreive data from DB")
@RequestMapping("/{id}")
public Account retrieve(@PathVariable Long id) {
    // ...
}

}

I have tried using below but its set only when the spring boot starts and takes changes only when the service is restarted next time ...

@Bean
public CorsFilter corsFilter() {
    UrlBasedCorsConfigurationSource source = new UrlBasedCorsConfigurationSource();
   // CorsConfiguration config = jHipsterProperties.getCors();

       CorsConfiguration config=CorsService.fetchCorsConfigFromDb;
    if (config.getAllowedOrigins() != null && !config.getAllowedOrigins().isEmpty()) {
        log.debug("Registering CORS filter");
        source.registerCorsConfiguration("/api/**", config);
        source.registerCorsConfiguration("/management/**", config);
        source.registerCorsConfiguration("/v2/api-docs", config);
    }
    return new CorsFilter(source);
}

fetchCorsConfigFromDb will fetch data from DB. Any changes from DB will be reflected only when Spring Boot App is restarted...

Answer 1

To implement this functionality you can use a basic filter in which you can write your custom database logic to add CORS header to your request based on some database attribute value.

You can refer to below example to implement this functionality using spring-data-jpa.

Add DB connection attributes to application.properties file

application.properties

spring.jpa.database=POSTGRESQL
spring.jpa.show-sql=false
spring.jpa.hibernate.ddl-auto=update

spring.datasource.driverClassName=org.postgresql.Driver
spring.datasource.url=jdbc:postgresql://localhost:5432/testdb
spring.datasource.username=postgres
spring.datasource.password=root

Create a entity with below attribute to save URL in DB

Cors.java

@Entity
@Getter
@Setter
public class Cors {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private long id;
    private String url;
    private boolean isAllowed;
}

And in the repository added a findByUrl method to get value from DB based on URL

CorsRepository.java

public interface CorsRepository extends JpaRepository<Cors,Long> {
    Optional<Cors> findByUrl(String url);
}

Below is my filter to intercept request and make DB call and if isAllowed is true then i add cors headers to make a successful request

CorsFilter.java

@Component
public class CorsFilter implements Filter {
    @Autowired
    CorsRepository corsRepository;

    @Override
    public void init(FilterConfig filterConfig) throws ServletException { }

    @Override
    public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException {
        HttpServletRequest request = (HttpServletRequest) req;
        String url = request.getRequestURI().toString();
        System.out.println(url);

        Optional<Cors> cors = corsRepository.findByUrl(url);
        if(cors.isPresent() && cors.get().isAllowed()){
            HttpServletResponse response = (HttpServletResponse) res;

            response.setHeader("Access-Control-Allow-Origin", request.getHeader("Origin"));
            response.setHeader("Access-Control-Allow-Credentials", "true");
            response.setHeader("Access-Control-Allow-Methods", "POST, GET, OPTIONS, DELETE");
            response.setHeader("Access-Control-Max-Age", "3600");
            response.setHeader("Access-Control-Allow-Headers", "Content-Type, Accept, X-Requested-With, remember-me");
        }
        chain.doFilter(req, res);
    }

    @Override
    public void destroy() { }
}

You can create a sample controller like this:

CorsTesterController.java

@RestController
public class CorsTesterController {

    @GetMapping("/api/v1/test")
    String getResponse(){
        return "test response";
    }
}

and insert values to DB to allow/disallow a url to test this example code.

testdb=# select * from cors;
 id | is_allowed |       url
----+------------+-----------------
  1 | f          | /api/v1/block
  2 | t          | /api/v1/allowed

Answer 2

For CorsService.fetchCorsConfigFromDb; it should load from cache

then you can update your cache at run-time

you should implement CorsService.fetchCorsConfig();

1. this method should look for any cors configuration in cache first ,if there any configurations found load it directly from cache else you will retrive cors from db and update your cache
2. create update cors at runtime method CorsService.updateCorsConfig(); , this should update your cors in db and then update cache .

Answer 3

Usually reading properties from database - not secured variant and if you lost connection to database you service can startup not correct.

Anyway you can do it, but would like to draw attention to default support by Spring a lot of remote properties sources

For loading custom properties you may use
spring.config.import=optional:file:./cors.yml
or from java args
-Dspring.config.import=optional:file:./cors.yml
This method support reading from file, from url, config server
Spring documentation about this

For reading CORS configuration from properties file you may use library (I'm developer of this)

<dependency>
  <groupId>io.github.iruzhnikov</groupId>
  <artifactId>spring-webmvc-cors-properties-autoconfigure</artifactId>
  <version>VERSION</version>
</dependency>

and properties config

spring:
  web:
    cors:
      enabled: true
      mappings: #spring.web.cors.mappings.<any_name>.<property>: <value>
        anyName: #just any name, just for grouping properties under the same path pattern (not used in internal logic)
          paths: #ant style path pattern, ATTENTION! not ordered, /** pattern override all other pattern
            - /path/to/api
            - /path/to/api/**
          #allowed-origins: "*"
          allowed-methods: GET #Enable override all defaults! If disabled: a lot more from all the controller methods included from the path pattern matches
          #allowed-headers: "*"
          #exposed-headers: ('*' - not-supported)
          #allow-credentials: true
          allowed-origin-patterns: .*
          #max-age: PT30M

Answer 4

Your array needs to be at least twice as big as the number of items in your list. You may find this approach useful:

from multiprocessing import Process, Array


def calculation(numbers, result):
    for index, number in enumerate(numbers):
        result[index] = number*number


def calculation2(numbers, result):
    for index, number in enumerate(numbers, len(numbers)):
        result[index] = number*number*number


if __name__ == '__main__':
    nums = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
    result = Array('i', len(nums)*2)
    p = []
    for t in [calculation, calculation2]:
        p.append(Process(target=t, args=(nums, result)))
        p[-1].start()
    for p_ in p:
        p_.join()

    print(result[:])

Output:

[1, 4, 9, 16, 25, 36, 49, 64, 81, 100, 1, 8, 27, 64, 125, 216, 343, 512, 729, 1000]