如果一個bean實現FactoryBean，那麼它就不是一個簡單的bean，類似於java模式中的工廠模式，用於生產不同的Object。

舉例

 public class OkHttpClientFactoryBean implements FactoryBean, DisposableBean {
	private int connectTimeout;
	private int readTimeout;
	private int writeTimeout;
	/**
	 * http proxy config
	 **/
	private String host;
	private int port;
 

	private String username;
	private String password;
	/**
	 * OkHttpClient instance
	 **/
	private OkHttpClient client;

	@Override
	public Object getObject() throws Exception {
		ConnectionPool pool = new ConnectionPool(5, 10, TimeUnit.SECONDS);
		OkHttpClient.Builder builder = new OkHttpClient.Builder
 
();
		builder.connectTimeout(connectTimeout, TimeUnit.MILLISECONDS).readTimeout(readTimeout, TimeUnit.MILLISECONDS).writeTimeout(writeTimeout, TimeUnit.MILLISECONDS).connectionPool(pool);
		if (StringUtils.isNotBlank(host) && port > 0) {
			Proxy proxy = new Proxy(Proxy.Type.HTTP, new InetSocketAddress
 
(host, port));
			builder.proxy(proxy);
		}
		if (StringUtils.isNotBlank(username) && StringUtils.isNotBlank(password)) {
			Authenticator proxyAuthenticator = new Authenticator() {
				@Override
				public Request authenticate(Route route, Response response) throws IOException {
					String credential = Credentials.basic(username, password);
					return response.request().newBuilder().header("Proxy-Authorization", credential).build();
				}
			};
			builder.proxyAuthenticator(proxyAuthenticator);
		}
		client = builder.build();
		return client;
	}

	@Override
	public Class<?> getObjectType() {
		return OkHttpClient.class;
	}

	@Override
	public boolean isSingleton() {
		return true;
	}

	@Override
	public void destroy() throws Exception {
		if (client != null) {
			client.connectionPool().evictAll();
			client.dispatcher().executorService().shutdown();
			client.cache().close();
			client = null;
		}
	}

	public void setConnectTimeout(int connectTimeout) {
		this.connectTimeout = connectTimeout;
	}

	public void setReadTimeout(int readTimeout) {
		this.readTimeout = readTimeout;
	}

	public void setWriteTimeout(int writeTimeout) {
		this.writeTimeout = writeTimeout;
	}

	public void setHost(String host) {
		this.host = host;
	}

	public void setPort(int port) {
		this.port = port;
	}

	public void setUsername(String username) {
		this.username = username;
	}

	public void setPassword(String password) {
		this.password = password;
	}
}