Java优化考虑构建器创建对象

来源：互联网发布：原生js 实现swipe效果编辑：程序博客网时间：2024/06/14 00:22

最近在做项目的时候，需要新建一个对象叫CartMessage。CartMessage只作为方法参数，如果要构建一个CartMessage,没有重构之前的做法是类似这样的：

CartMessage msg = new CartMessage();msg.setA();msg.setB();msg.setC();...helpCartService.sendMsgToWebSocket(msg);

发现用set的方法比较累赘，占用多行，写起来不简洁。忽略想去Java Effecttive书中关于构建对象的建议。想起了构建器方式。首先在CartMessage中加入Builder构建器：

    public static class Builder{        private CartMessage cartMessage;        public Builder(){            cartMessage = new CartMessage();        }        public Builder entityId(String entityId){            cartMessage.setEntityId(entityId);            return this;        }        public Builder seatCode(String seatCode){            cartMessage.setSeatCode(seatCode);            return this;        }        public Builder customerId(String customerId){            cartMessage.setCustomerRegisterId(customerId);            return this;        }        public Builder orderId(String orderId){            cartMessage.setOrderId(orderId);            return this;        }        public CartMessage build(){            return cartMessage;        }    }

重构之后，只要一行代码就行了，而且清晰明了：

helpCartService.sendMsgToWebSocket(new CartMessage.Builder().                    entityId(entityId).seatCode(seatCode).customerId(customerRegisterId).orderId(orderId).build());

构建器有很多变形，灵活多变，例如zookeeper客户端Curator中client的创建也是用构建器：

    static CuratorFramework client = CuratorFrameworkFactory.builder()            .connectString("localhost:2181")            .sessionTimeoutMs(5000)            .retryPolicy(retryPolicy)            .build();

builder()是个静态方法，返回一个构建器:

   public static Builder builder()    {        return new Builder();    }

构建器如下：

 public static class Builder    {        private EnsembleProvider ensembleProvider;        private int sessionTimeoutMs = DEFAULT_SESSION_TIMEOUT_MS;        private int connectionTimeoutMs = DEFAULT_CONNECTION_TIMEOUT_MS;        private int maxCloseWaitMs = DEFAULT_CLOSE_WAIT_MS;        private RetryPolicy retryPolicy;        private ThreadFactory threadFactory = null;        private String namespace;        private List<AuthInfo> authInfos = null;        private byte[] defaultData = LOCAL_ADDRESS;        private CompressionProvider compressionProvider = DEFAULT_COMPRESSION_PROVIDER;        private ZookeeperFactory zookeeperFactory = DEFAULT_ZOOKEEPER_FACTORY;        private ACLProvider aclProvider = DEFAULT_ACL_PROVIDER;        private boolean canBeReadOnly = false;        /**         * Apply the current values and build a new CuratorFramework         *         * @return new CuratorFramework         */        public CuratorFramework build()        {            return new CuratorFrameworkImpl(this);        }        /**         * Apply the current values and build a new temporary CuratorFramework. Temporary         * CuratorFramework instances are meant for single requests to ZooKeeper ensembles         * over a failure prone network such as a WAN. The APIs available from {@link CuratorTempFramework}         * are limited. Further, the connection will be closed after 3 minutes of inactivity.         *         * @return temp instance         */        public CuratorTempFramework buildTemp()        {            return buildTemp(DEFAULT_INACTIVE_THRESHOLD_MS, TimeUnit.MILLISECONDS);        }...

可以看出builder有很多构建方式，如buildTemp()构建临时对象，build()创建了一个实现类等。有兴趣的话自己可以看看源码。

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