Java Curator Framework detailed and use examples
Java Curator Framework Detailed Example and Use Example
Java Curator Framework is a high -end Java library for interaction with Apachekeeeper.Zookeeper is a distributed coordinated service that can be used to build highly available distributed systems.Curator Framework simplifies the interaction process with Zookeeper, and provides simple and powerful APIs to handle various operations of Zookeeper.
This article will introduce the usage of Java Curator Framework in detail and provide some code examples to illustrate its functions and uses.
1. Introduce Curator Framework
To use Curator Framework, you need to introduce it into the project first.You can use Maven or Gradle to add the following dependencies:
Maven：
<dependency>
<groupId>org.apache.curator</groupId>
<artifactId>curator-framework</artifactId>
<version>5.2.0</version>
</dependency>
Gradle：
gradle
implementation 'org.apache.curator:curator-framework:5.2.0'
2. Create Zookeeper client
Before using Curator Framework to interact with Zookeeper, you need to create a Zookeeper client.The following is an example of creating a client:
String connectionString = "LOCALHOST: 2181"; // Zookeeper server address
int sessionTimeoutms = 5000; // Session timeout time, in milliseconds
int ConnectionTimeoutms = 5000; // Connect timeout time, in milliseconds
RetryPolicy RetryPolicy = New ExponentialBackoffretry (1000, 3); // Review strategy, here is the index retreating the re -trial
CuratorFramework client = CuratorFrameworkFactory.newClient(connectionString, sessionTimeoutMs, connectionTimeoutMs, retryPolicy);
client.start (); // Start the client
3. Create nodes
Use Curator Framework to easily create nodes in Zookeeper.The following is an example of creating nodes:
String path = "/example/node"; // node path
byte [] data = "Hello, world!". Getbytes (); // Node data
client.create().creatingParentsIfNeeded().forPath(path, data);
In the above example, we use the method to ensure that the parent node is automatically created when creating nodes (if they do not exist) when creating nodes.
4. Read node data
To read the data of the Zookeeper node, you can use the `getData () method provided by Curator Framework.The following is a simple example:
String path = "/example/node"; // node path
byte[] data = client.getData().forPath(path);
String dataString = new String(data);
System.out.println("Node data: " + dataString);
5. Monitoring node changes
Curator Framework also provides the monitoring function of changes in nodes.You can use the `NodeCache` class to monitor the creation, update and deletion of the Zookeeper node.The following is an example of the change of the monitor node:
String path = "/example/node"; // node path
NodeCache nodeCache = new NodeCache(client, path);
nodeCache.start();
nodeCache.getListenable().addListener(() -> {
if (nodeCache.getCurrentData() != null) {
String data = new String(nodeCache.getCurrentData().getData());
System.out.println("Node data changed: " + data);
} else {
System.out.println("Node deleted");
}
});
In the above example, we created an instance of `nodeCache` and added a callback function to handle the change event of the node.When the node data changes, the callback function will be triggered.
Through the above example, we briefly introduced the basic usage of Java Curator Framework.With Curator Framework, we can easily create, read and monitor the Zookeeper node.In addition, Curator Framework also provides more advanced features, such as distributed locks, distributed counter, etc., which can help developers build a reliable distributed system.
