KEYCLOAK-1901: Add a Keycloak client builder

Adds support for creating a Keycloak client using the builder
pattern and supports customizing the underlying ResteasyClient
used for connecting to the Keycloak server.

integration/admin-client/src/main/java/org/keycloak/admin/client/Keycloak.java

@@ -9,6 +9,12 @@ import org.keycloak.admin.client.resource.RealmsResource;
 import org.keycloak.admin.client.token.TokenManager;
 
 /**
+ * Provides a Keycloak client. By default, this implementation uses a {@link ResteasyClient RESTEasy client} with the
+ * default {@link ResteasyClientBuilder} settings. To customize the underling client, use a {@link KeycloakBuilder} to
+ * create a Keycloak client.
+ *
+ * @see KeycloakBuilder
+ *
  * @author rodrigo.sasaki@icarros.com.br
  */
 public class Keycloak {
@@ -18,9 +24,9 @@ public class Keycloak {
     private final ResteasyWebTarget target;
     private final ResteasyClient client;
 
-    private Keycloak(String serverUrl, String realm, String username, String password, String clientId, String clientSecret){
+    Keycloak(String serverUrl, String realm, String username, String password, String clientId, String clientSecret, ResteasyClient resteasyClient){
         config = new Config(serverUrl, realm, username, password, clientId, clientSecret);
-        client = new ResteasyClientBuilder().build();
+        client = resteasyClient != null ? resteasyClient : new ResteasyClientBuilder().build();
 
         tokenManager = new TokenManager(config, client);
 
@@ -30,11 +36,11 @@ public class Keycloak {
     }
 
     public static Keycloak getInstance(String serverUrl, String realm, String username, String password, String clientId, String clientSecret){
-        return new Keycloak(serverUrl, realm, username, password, clientId, clientSecret);
+        return new Keycloak(serverUrl, realm, username, password, clientId, clientSecret, null);
     }
 
     public static Keycloak getInstance(String serverUrl, String realm, String username, String password, String clientId){
-        return new Keycloak(serverUrl, realm, username, password, clientId, null);
+        return new Keycloak(serverUrl, realm, username, password, clientId, null, null);
     }
 
     public RealmsResource realms(){
@@ -49,6 +55,9 @@ public class Keycloak {
         return tokenManager;
     }
 
+    /**
+     * Closes the underlying client. After calling this method, this <code>Keycloak</code> instance cannot be reused.
+     */
     public void close() {
         client.close();
     }

integration/admin-client/src/main/java/org/keycloak/admin/client/KeycloakBuilder.java

@@ -0,0 +1,107 @@
+package org.keycloak.admin.client;
+
+import org.jboss.resteasy.client.jaxrs.ResteasyClient;
+import org.jboss.resteasy.client.jaxrs.ResteasyClientBuilder;
+
+/**
+ * Provides a {@link Keycloak} client builder with the ability to customize the underlying
+ * {@link ResteasyClient RESTEasy client} used to communicate with the Keycloak server.
+ *
+ * <p>Example usage with a connection pool size of 20:</p>
+ *
+ * <pre>
+ *   Keycloak keycloak = KeycloakBuilder.builder()
+ *     .serverUrl("https:/sso.example.com/auth")
+ *     .realm("realm")
+ *     .username("user")
+ *     .password("pass")
+ *     .clientId("client")
+ *     .clientSecret("secret")
+ *     .resteasyClient(new ResteasyClientBuilder().connectionPoolSize(20).build())
+ *     .build();
+ * </pre>
+ *
+ * @author Scott Rossillo
+ * @see ResteasyClientBuilder
+ */
+public class KeycloakBuilder {
+    private String serverUrl;
+    private String realm;
+    private String username;
+    private String password;
+    private String clientId;
+    private String clientSecret;
+    private ResteasyClient resteasyClient;
+
+    public KeycloakBuilder serverUrl(String serverUrl) {
+        this.serverUrl = serverUrl;
+        return this;
+    }
+
+    public KeycloakBuilder realm(String realm) {
+        this.realm = realm;
+        return this;
+    }
+
+    public KeycloakBuilder username(String username) {
+        this.username = username;
+        return this;
+    }
+
+    public KeycloakBuilder password(String password) {
+        this.password = password;
+        return this;
+    }
+
+    public KeycloakBuilder clientId(String clientId) {
+        this.clientId = clientId;
+        return this;
+    }
+
+    public KeycloakBuilder clientSecret(String clientSecret) {
+        this.clientSecret = clientSecret;
+        return this;
+    }
+
+    public KeycloakBuilder resteasyClient(ResteasyClient resteasyClient) {
+        this.resteasyClient = resteasyClient;
+        return this;
+    }
+
+    /**
+     * Builds a new Keycloak client from this builder.
+     */
+    public Keycloak build() {
+        if (serverUrl == null) {
+            throw new IllegalStateException("serverUrl required");
+        }
+
+        if (realm == null) {
+            throw new IllegalStateException("realm required");
+        }
+
+        if (username == null) {
+            throw new IllegalStateException("username required");
+        }
+
+        if (password == null) {
+            throw new IllegalStateException("password required");
+        }
+
+        if (clientId == null) {
+            throw new IllegalStateException("clientId required");
+        }
+
+        return new Keycloak(serverUrl, realm, username, password, clientId, clientSecret, resteasyClient);
+    }
+
+    private KeycloakBuilder() {
+    }
+
+    /**
+     * Returns a new Keycloak builder.
+     */
+    public static KeycloakBuilder builder() {
+        return new KeycloakBuilder();
+    }
+}