如何封装client/tool

单例

工具类,模板类,可以确定只用生成一个实例的,考虑这种设计模式,善用例模式。

在类中构造方法善用重载

Demo

public class ZooKeeperTemplate implements AutoCloseable {
private static final Logger logger = LoggerFactory.getLogger(ZooKeeperTemplate.class);
/** zookeeper session timeout: 30 seconds */
private static final int DEFAULT_SESSION_TIMEOUT_MILLISECONDS = 30_000;
/** zookeeper connect timeout: 60 seconds */
private static final int DEFAULT_CONNECT_TIMEOUT_MILLISECONDS = 60_000;
/** znode path separator */
private static final String PATH_SEPARATOR = "/";
public static ZooKeeperTemplate getInstance(String zooKeeperHost) {
return getInstance(zooKeeperHost, null, null);
}
public static ZooKeeperTemplate getInstance(String zooKeeperHost, Integer sessionTimeoutMilliseconds, Integer connectTimeoutMilliseconds) {
return new ZooKeeperTemplate(zooKeeperHost, sessionTimeoutMilliseconds, connectTimeoutMilliseconds);
}
private final String zooKeeperHost;
private final Integer sessionTimeoutMilliseconds;
private final Integer connectTimeoutMilliseconds;
private final ZooKeeper zoo;
private ZooKeeperTemplate(String zooKeeperHost, Integer sessionTimeoutMilliseconds, Integer connectTimeoutMilliseconds) {
this.zooKeeperHost = zooKeeperHost;
this.sessionTimeoutMilliseconds = defaultValue(sessionTimeoutMilliseconds, DEFAULT_SESSION_TIMEOUT_MILLISECONDS);
this.connectTimeoutMilliseconds = defaultValue(connectTimeoutMilliseconds, DEFAULT_CONNECT_TIMEOUT_MILLISECONDS);
this.zoo = connect();
}
//TODO 省略
}

Builder构建器

这个设计模式也是数据创建型的,如果参与大于4个,推荐使用这种模式。

Demo

public class RedisTemplate implements Closeable {
private JedisCluster jedisCluster;
private String keyPrefix;
private static String clientName = "xaecbd-sns";
private RedisTemplate(RedisBuilder builder) {
final String[] hosts = builder.hosts.split(RedisConstants.HOST_SPLIT);
keyPrefix = builder.prefix;
Set<HostAndPort> nodes = new HashSet<HostAndPort>() {
private static final long serialVersionUID = 5341345879054512402L;
{
for (String hostAndPort : hosts) {
String[] array = hostAndPort.split(":");
if (array.length > 1) {
add(new HostAndPort(array[0], Integer.parseInt(array[1])));
} else {
add(new HostAndPort(array[0], RedisConstants.DEFAULT_PORT));
}
}
}
};
this.jedisCluster = new JedisCluster(nodes, builder.timeout, builder.timeout, builder.retry, builder.password, clientName,new GenericObjectPoolConfig<Jedis>());
}
//TODO 省略其他逻辑代码
public static class Builder {
private String hosts;
private String prefix;
private int timeout = BinaryJedisCluster.DEFAULT_TIMEOUT;
private int retry = BinaryJedisCluster.DEFAULT_MAX_ATTEMPTS;
private String password = null;
public RedisBuilder(String hosts) {
this.hosts = hosts;
}
public RedisBuilder timeout(int timeout) {
this.timeout = timeout;
return this;
}
public RedisBuilder retry(int retry) {
this.retry = retry;
return this;
}
public RedisBuilder password(String password) {
this.password = password;
return this;
}
public RedisBuilder keyPrefix(String prefix) {
this.prefix = prefix;
return this;
}
public RedisTemplate builder() {
return new RedisTemplate(this);
}
}
}

封装技巧

返回值

使用Optinal包装返回值,避免返回值为null

统一校验

在类中的多个方法都需要相同的参数校验的,抽象出统一校验,jdk源码中就存在大量这样的例子。

下面举个例子:

private void assertConnected() {
if(zoo == null) {
throw new SnsException("ZooKeeper is not connected");
}
}
private void assertPathValid(String path) {
PathUtils.validatePath(path);
}
public void delete(String path) {
assertConnected();
assertPathValid(path);
//省略
}
public void create(String path) {
assertConnected();
assertPathValid(path);
//省略
}

AutoCloseable/Closeable

需要关闭资源的,记得实现AutoCloseable/Closeable