Merge pull request #513 from MaoJianwei/master

Add an usage for config listener. We can react to the change of config data.

spring-cloud-alibaba-examples/nacos-example/nacos-config-example/src/main/java/org/springframework/cloud/alibaba/cloud/examples/Application.java

@@ -1,17 +1,24 @@
 package org.springframework.cloud.alibaba.cloud.examples;
 
+import com.alibaba.nacos.api.config.listener.Listener;
+import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.beans.factory.annotation.Value;
 import org.springframework.boot.ApplicationArguments;
 import org.springframework.boot.ApplicationRunner;
 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.SpringBootApplication;
+import org.springframework.cloud.alibaba.nacos.NacosConfigProperties;
 import org.springframework.cloud.context.config.annotation.RefreshScope;
 import org.springframework.stereotype.Component;
 import org.springframework.web.bind.annotation.RequestMapping;
 import org.springframework.web.bind.annotation.RestController;
 
+import java.util.HashMap;
+import java.util.Map;
+import java.util.concurrent.Executor;
+
 /**
- * @author xiaojing
+ * @author xiaojing, Jianwei Mao
  */
 @SpringBootApplication
 public class Application {
@@ -27,13 +34,48 @@ class SampleRunner implements ApplicationRunner {
 	@Value("${user.name}")
 	String userName;
 
-	@Value("${user.age}")
+	@Value("${user.age:25}")
 	int userAge;
 
+
+    @Autowired
+    private NacosConfigProperties nacosConfigProperties;
+
 	@Override
 	public void run(ApplicationArguments args) throws Exception {
-		System.out.println(userName);
-		System.out.println(userAge);
+		System.out.println(String.format("Initial username=%s, userAge=%d", userName, userAge));
+
+		nacosConfigProperties.configServiceInstance()
+                .addListener("nacos-config-example.properties", "DEFAULT_GROUP", new Listener() {
+
+                    /**
+                     * Callback with latest config data.
+                     *
+                     * For example, config data in Nacos is:
+                     *
+                     *     user.name=Nacos
+                     *     user.age=25
+                     *
+                     * @param configInfo latest config data for specific dataId in Nacos server
+                     */
+                    @Override
+                    public void receiveConfigInfo(String configInfo) {
+                        String [] configLines = configInfo.split("\r\n");
+                        Map<String, String> configs = new HashMap<>();
+                        for (String c : configLines) {
+                            String [] configPair = c.split("=");
+                            configs.put(configPair[0], configPair[1]);
+                        }
+
+                        System.out.println(String.format("Latest username=%s, userAge=%s",
+                                configs.get("user.name"), configs.get("user.age")));
+                    }
+
+                    @Override
+                    public Executor getExecutor() {
+                        return null;
+                    }
+                });
 	}
 }
 
@@ -44,7 +86,7 @@ class SampleController {
 	@Value("${user.name}")
 	String userName;
 
-	@Value("${user.age}")
+	@Value("${user.age:25}")
 	int age;
 
 	@RequestMapping("/user")