[Java][apache-httpclient][feign][okhttp-gson] Enable access token refresh (#17086)

* add setter of bearer token supplier

* run generate-samples.sh

* add test of bearer auth

samples/client/echo_api/java/okhttp-gson/src/main/java/org/openapitools/client/ApiClient.java

@@ -47,6 +47,7 @@ import java.time.format.DateTimeFormatter;
 import java.util.*;
 import java.util.Map.Entry;
 import java.util.concurrent.TimeUnit;
+import java.util.function.Supplier;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
@@ -386,14 +387,23 @@ public class ApiClient {
         return authentications.get(authName);
     }
 
-        /**
-        * Helper method to set access token for the first Bearer authentication.
-        * @param bearerToken Bearer token
-        */
+    /**
+     * Helper method to set access token for the first Bearer authentication.
+     * @param bearerToken Bearer token
+     */
     public void setBearerToken(String bearerToken) {
+        setBearerToken(() -> bearerToken);
+    }
+
+    /**
+     * Helper method to set the supplier of access tokens for Bearer authentication.
+     *
+     * @param tokenSupplier The supplier of bearer tokens
+     */
+    public void setBearerToken(Supplier<String> tokenSupplier) {
         for (Authentication auth : authentications.values()) {
             if (auth instanceof HttpBearerAuth) {
-                ((HttpBearerAuth) auth).setBearerToken(bearerToken);
+                ((HttpBearerAuth) auth).setBearerToken(tokenSupplier);
                 return;
             }
         }

samples/client/echo_api/java/okhttp-gson/src/main/java/org/openapitools/client/auth/HttpBearerAuth.java

@@ -17,13 +17,15 @@ import org.openapitools.client.ApiException;
 import org.openapitools.client.Pair;
 
 import java.net.URI;
-import java.util.Map;
 import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+import java.util.function.Supplier;
 
 @javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen")
 public class HttpBearerAuth implements Authentication {
   private final String scheme;
-  private String bearerToken;
+  private Supplier<String> tokenSupplier;
 
   public HttpBearerAuth(String scheme) {
     this.scheme = scheme;
@@ -35,7 +37,7 @@ public class HttpBearerAuth implements Authentication {
    * @return The bearer token
    */
   public String getBearerToken() {
-    return bearerToken;
+    return tokenSupplier.get();
   }
 
   /**
@@ -44,12 +46,22 @@ public class HttpBearerAuth implements Authentication {
    * @param bearerToken The bearer token to send in the Authorization header
    */
   public void setBearerToken(String bearerToken) {
-    this.bearerToken = bearerToken;
+    this.tokenSupplier = () -> bearerToken;
+  }
+
+  /**
+   * Sets the supplier of tokens, which together with the scheme, will be sent as the value of the Authorization header.
+   *
+   * @param tokenSupplier The supplier of bearer tokens to send in the Authorization header
+   */
+  public void setBearerToken(Supplier<String> tokenSupplier) {
+    this.tokenSupplier = tokenSupplier;
   }
 
   @Override
   public void applyToParams(List<Pair> queryParams, Map<String, String> headerParams, Map<String, String> cookieParams,
                             String payload, String method, URI uri) throws ApiException {
+    String bearerToken = Optional.ofNullable(tokenSupplier).map(Supplier::get).orElse(null);
     if (bearerToken == null) {
       return;
     }