How to Add Custom header in spring boot and java

**Spring Boot (Java):**

In Spring Boot, you can add custom headers to HTTP responses using filters or interceptors. Here's an example of how you can do it using an interceptor:

1. Create a class that implements `HandlerInterceptor` interface:

```java

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import org.springframework.stereotype.Component;

import org.springframework.web.servlet.HandlerInterceptor;

@Component

public class CustomHeaderInterceptor implements HandlerInterceptor {

    @Override

    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) {

        response.addHeader("Custom-Header", "Header-Value");

        return true;

    }

}

```

2. Register the interceptor in your Spring Boot application:

```java

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.context.annotation.Configuration;

import org.springframework.web.servlet.config.annotation.InterceptorRegistry;

import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

@Configuration

public class WebConfig implements WebMvcConfigurer {

    @Autowired

    private CustomHeaderInterceptor customHeaderInterceptor;

    @Override

    public void addInterceptors(InterceptorRegistry registry) {

        registry.addInterceptor(customHeaderInterceptor);

    }

}

```

Now, every HTTP response from your Spring Boot application will include the custom header `"Custom-Header"` with the value `"Header-Value"`.

**Angular (TypeScript):**

In Angular, you can add custom headers to HTTP requests using an `HttpInterceptor`. Here's an example of how to create one:

1. Create an interceptor:

```typescript

import { Injectable } from '@angular/core';

import { HttpInterceptor, HttpRequest, HttpHandler, HttpEvent } from '@angular/common/http';

import { Observable } from 'rxjs';

@Injectable()

export class CustomHttpInterceptor implements HttpInterceptor {

    intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {

        const modifiedReq = req.clone({

            setHeaders: {

                'Custom-Header': 'Header-Value'

            }

        });

        return next.handle(modifiedReq);

    }

}

```

2. Provide the interceptor in your Angular module:

```typescript

import { BrowserModule } from '@angular/platform-browser';

import { NgModule } from '@angular/core';

import { HttpClientModule, HTTP_INTERCEPTORS } from '@angular/common/http';

import { AppComponent } from './app.component';

import { CustomHttpInterceptor } from './custom-http-interceptor';

@NgModule({

  declarations: [

    AppComponent

  ],

  imports: [

    BrowserModule,

    HttpClientModule

  ],

  providers: [

    { provide: HTTP_INTERCEPTORS, useClass: CustomHttpInterceptor, multi: true }

  ],

  bootstrap: [AppComponent]

})

export class AppModule { }

```

Now, every HTTP request from your Angular application will include the custom header `"Custom-Header"` with the value `"Header-Value"`.

These examples demonstrate how to add custom headers in Spring Boot (Java) and Angular (TypeScript).