Merge pull request #3042 from haoran-pku/master

Add SyncProducer Example

docs/cn/Example_Simple_cn.md

+# Basic Sample 
+------
+基本示例中提供了以下两个功能
+* RocketMQ可用于以三种方式发送消息：可靠的同步、可靠的异步和单向传输。前两种消息类型是可靠的，因为无论它们是否成功发送都有响应。
+* RocketMQ可以用来消费消息。
+### 1 添加依赖
+maven:
+``` java
+<dependency>
+  <groupId>org.apache.rocketmq</groupId>
+  <artifactId>rocketmq-client</artifactId>
+  <version>4.3.0</version>
+</dependency>
+```
+gradle: 
+``` java 
+compile 'org.apache.rocketmq:rocketmq-client:4.3.0'
+```
+### 2 发送消息
+##### 2.1 使用Producer发送同步消息
+可靠的同步传输被广泛应用于各种场景，如重要的通知消息、短消息通知等。
+``` java
+public class SyncProducer {
+  public static void main(String[] args) throws Exception {
+    // Instantiate with a producer group name
+    DefaultMQProducer producer = new DefaultMQProducer("please_rename_unique_group_name");
+    // Specify name server addresses
+    producer.setNamesrvAddr("localhost:9876");
+    // Launch the producer instance
+    producer.start();
+    for (int i = 0; i < 100; i++) {
+      // Create a message instance with specifying topic, tag and message body
+      Message msg = new Message("TopicTest" /* Topic */,
+        "TagA" /* Tag */,
+        ("Hello RocketMQ " + i).getBytes(RemotingHelper.DEFAULT_CHARSET) /* Message body */
+        );
+      // Send message to one of brokers
+      SendResult sendResult = producer.send(msg);
+      // Check whether the message has been delivered by the callback of sendResult
+      System.out.printf("%s%n", sendResult);
+    }
+    // Shut down once the producer instance is not longer in use
+    producer.shutdown();
+  }
+}
+```
+##### 2.2 发送异步消息
+异步传输通常用于响应时间敏感的业务场景。这意味着发送方无法等待代理的响应太长时间。
+``` java
+public class AsyncProducer {
+  public static void main(String[] args) throws Exception {
+    // Instantiate with a producer group name
+    DefaultMQProducer producer = new DefaultMQProducer("please_rename_unique_group_name");
+    // Specify name server addresses
+    producer.setNamesrvAddr("localhost:9876");
+    // Launch the producer instance
+    producer.start();
+    producer.setRetryTimesWhenSendAsyncFailed(0);
+    for (int i = 0; i < 100; i++) {
+      final int index = i;
+      // Create a message instance with specifying topic, tag and message body
+      Message msg = new Message("TopicTest",
+        "TagA",
+        "OrderID188",
+        "Hello world".getBytes(RemotingHelper.DEFAULT_CHARSET));
+      // SendCallback: receive the callback of the asynchronous return result.
+      producer.send(msg, new SendCallback() {
+        @Override
+        public void onSuccess(SendResult sendResult) {
+          System.out.printf("%-10d OK %s %n", index,
+            sendResult.getMsgId());
+        }
+        @Override
+        public void onException(Throwable e) {
+          System.out.printf("%-10d Exception %s %n", index, e);
+          e.printStackTrace();
+        }
+      });
+    }
+    // Shut down once the producer instance is not longer in use
+    producer.shutdown();
+  }
+}
+```
+##### 2.3 以单向模式发送消息
+单向传输用于需要中等可靠性的情况，如日志收集。
+``` java
+public class OnewayProducer {
+  public static void main(String[] args) throws Exception{
+    // Instantiate with a producer group name
+    DefaultMQProducer producer = new DefaultMQProducer("please_rename_unique_group_name");
+    // Specify name server addresses
+    producer.setNamesrvAddr("localhost:9876");
+    // Launch the producer instance
+    producer.start();
+    for (int i = 0; i < 100; i++) {
+      // Create a message instance with specifying topic, tag and message body
+      Message msg = new Message("TopicTest" /* Topic */,
+        "TagA" /* Tag */,
+        ("Hello RocketMQ " + i).getBytes(RemotingHelper.DEFAULT_CHARSET) /* Message body */
+      );
+      // Send in one-way mode, no return result
+      producer.sendOneway(msg);
+    }
+    // Shut down once the producer instance is not longer in use
+     producer.shutdown();
+  }
+}
+```
+### 3 消费消息
+``` java
+public class Consumer {
+  public static void main(String[] args) throws InterruptedException, MQClientException {
+    // Instantiate with specified consumer group name
+    DefaultMQPushConsumer consumer = new DefaultMQPushConsumer("please_rename_unique_group_name");
+    
+    // Specify name server addresses
+    consumer.setNamesrvAddr("localhost:9876");
+
+    // Subscribe one or more topics and tags for finding those messages need to be consumed
+    consumer.subscribe("TopicTest", "*");
+    // Register callback to execute on arrival of messages fetched from brokers
+    consumer.registerMessageListener(new MessageListenerConcurrently() {
+      @Override
+      public ConsumeConcurrentlyStatus consumeMessage(List<MessageExt> msgs, ConsumeConcurrentlyContext context) {
+        System.out.printf("%s Receive New Messages: %s %n", Thread.currentThread().getName(), msgs);
+        // Mark the message that have been consumed successfully
+        return ConsumeConcurrentlyStatus.CONSUME_SUCCESS;
+      }
+    });
+    // Launch the consumer instance
+    consumer.start();
+    System.out.printf("Consumer Started.%n");
+  }
+}
+```
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