如何提取try catch outside方法?

Question

我有这个方法sendParameterValueAsMQTTMessage()，我使用它通过MQTT发布关于特定主题的消息。我使用try catch两次之后另一个(没有嵌套)，但它仍然看起来有些丑陋和拥挤的方法。我读了一篇关于整洁代码的文章，其中Bob大叔谈到了提取try catch的主体，但是我似乎没有很好地理解它，或者至少对我来说没有。

我怎么能摆脱try catch在我的方法提取它在外面?

public void sendParameterValueAsMQTTMessage() {
String payload = null;
try {
payload = convertToJSONString("range", String.valueOf(range));
} catch (JSONException e) {
this.logger.log(Level.ERROR, e);
}
MQTTMessage message = new MQTTMessage(MQTTTopics.RANGE_TOPIC,payload,0);
try {
this.client.publish(message);
Thread.sleep(3000);
} catch (Exception e) {
this.logger.log(Level.ERROR, e);
}
}

Answer 1

所提供的代码存在多个不同的问题，以下是我将如何重构它:

public void sendParameterValueAsMQTTMessage() {
final String payload = tryGetPayloadAsJson();
if (payload != null) {
trySendPayloadViaMQTT(payload);
}
}
private String tryGetPayloadAsJson() {
try {
return convertToJSONString("range", String.valueOf(range));
} catch (JSONException e) {
this.logger.log(Level.ERROR, e);
}
return null;
}
private void trySendPayloadViaMQTT(final String payload) {
try {
final MQTTMessage message = new MQTTMessage(MQTTTopics.RANGE_TOPIC, payload, 0);
this.client.publish(message);
Thread.sleep(3000);
} catch (Exception e) {
this.logger.log(Level.ERROR, e);
}
}

根据Bob叔叔的建议，这里可以改进的一件事是将try/catch移到trySendPayloadViaMQTT之外，像这样:

public void sendParameterValueAsMQTTMessage() {
final String payload = tryGetPayloadAsJson();
if (payload != null) {
trySendPayloadViaMQTT(payload);
}
}
private String tryGetPayloadAsJson() {
try {
return convertToJSONString("range", String.valueOf(range));
} catch (JSONException e) {
this.logger.log(Level.ERROR, e);
}
return null;
}
private void trySendPayloadViaMQTT(final String payload) {
try {
sendPayloadViaMQTT(payload);
} catch (Exception e) {
this.logger.log(Level.ERROR, e);
}
}
private void sendPayloadViaMQTT(final String payload) {
final MQTTMessage message = new MQTTMessage(MQTTTopics.RANGE_TOPIC, payload, 0);
this.client.publish(message);
Thread.sleep(3000);
}

Answer 2

您可以将所有代码放在一个try块中并设置多个捕获，当发生异常时，与它相关的捕获将被执行，如:

try{    
int a[]=new int[5];    
a[5]=30/0;    
}    
catch(ArithmeticException e)  
{  
System.out.println("Arithmetic Exception occurs");  
}    
catch(ArrayIndexOutOfBoundsException e)  
{  
System.out.println("ArrayIndexOutOfBounds Exception occurs");  
}    

Answer 3

您可以在方法中使用单个通用catch来处理两种可能的异常，如下所示:

public void sendParameterValueAsMQTTMessage() {
String payload = null;
try {
payload = convertToJSONString("range", String.valueOf(range));
MQTTMessage message = new MQTTMessage(MQTTTopics.RANGE_TOPIC,payload,0);
this.client.publish(message);
Thread.sleep(3000);
} catch (Exception e) {
this.logger.log(Level.ERROR, e);
}
}

Answer 4

public void sendParameterValueAsMQTTMessage() {
String payload = null;
try {
payload = convertToJSONString("range", String.valueOf(range));
} catch (JSONException e) {
this.logger.log(Level.ERROR, e);
}
MQTTMessage message = new MQTTMessage(MQTTTopics.RANGE_TOPIC,payload,0);
publishMessage(message); //extracted in a new method
}
public void publishMessage(MQTTMessage message){
try {
this.client.publish(message);
Thread.sleep(3000);
} catch (Exception e) {
this.logger.log(Level.ERROR, e);
}
}