Spring Batch的入門實例請參考我的另一篇文章:
http://blog.csdn.net/limiteewaltwo/article/details/8832771
把log4j的輸出級別定義爲info級別。
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">
<log4j:configuration xmlns:log4j='http://jakarta.apache.org/log4j/'>
<appender name="CONSOLE" class="org.apache.log4j.ConsoleAppender">
<param name="Target" value="System.out" />
<layout class="org.apache.log4j.PatternLayout">
<param name="ConversionPattern" value="%p [%c] - %m%n" />
</layout>
<!--過濾器設置輸出的級別 -->
<filter class="org.apache.log4j.varia.LevelRangeFilter">
<param name="levelMin" value="DEBUG" />
<param name="levelMax" value="ERROR" />
</filter>
</appender>
<!-- 根logger的設置 -->
<root>
<priority value="INFO" />
<appender-ref ref="CONSOLE"/>
</root>
</log4j:configuration>
重試的代碼示例:
/**
*
*/
package com.test.springbatch;
import java.util.HashMap;
import java.util.Map;
import org.apache.log4j.Logger;
import org.springframework.batch.retry.RetryCallback;
import org.springframework.batch.retry.RetryContext;
import org.springframework.batch.retry.policy.SimpleRetryPolicy;
import org.springframework.batch.retry.support.RetryTemplate;
/**
* @author hadoop
*
*/
public class RetryTest {
private static Logger logger = Logger.getLogger(RetryTest.class);
/**
* @param args
*/
public static void main(String[] args) {
/**
* SimpleRetryPolicy策略,重試固定的次數,包括第一次執行;
*/
SimpleRetryPolicy policy = new SimpleRetryPolicy();
/**
* 最多嘗試次數,第一次的序號爲0,5表示共嘗試5次(包括原始的第一次執行)。
*/
policy.setMaxAttempts(5);
Map<Class<? extends Throwable>,Boolean> retryExceptionMap = new HashMap<Class<? extends Throwable>,Boolean>();
/**
* 設置發生哪些異常時,重試
*/
retryExceptionMap.put(Exception.class, true);
policy.setRetryableExceptions(retryExceptionMap);
RetryTemplate template = new RetryTemplate();
template.setRetryPolicy(policy);
boolean runResult = false;
try {
runResult = template.execute(new RetryCallback<Boolean>(){
private int count = 0;
public Boolean doWithRetry(RetryContext context) throws Exception {
count++;
if(count < 5)
{
logger.info("exception happen" + count);
throw new Exception("exception happen" + count);
}
logger.info("here" + count);
return true;
}
});
} catch (Exception e) {
e.printStackTrace();
}
if(runResult)
{
logger.info("成功");
}
else
{
logger.info("失敗");
}
}
}
設計的情形爲,前4次拋出異常,第五次執行成功,執行代碼,我們得到如下的輸出:
INFO [com.test.springbatch.RetryTest] - exception happen1
INFO [com.test.springbatch.RetryTest] - exception happen2
INFO [com.test.springbatch.RetryTest] - exception happen3
INFO [com.test.springbatch.RetryTest] - exception happen4
INFO [com.test.springbatch.RetryTest] - here5
INFO [com.test.springbatch.RetryTest] - 成功
第五次執行成功,符合我們設想的結果。
如果把重試次數改爲4,會發生什麼呢。
policy.setMaxAttempts(4);
執行結果如下:
INFO [com.test.springbatch.RetryTest] - exception happen1
INFO [com.test.springbatch.RetryTest] - exception happen2
INFO [com.test.springbatch.RetryTest] - exception happen3
INFO [com.test.springbatch.RetryTest] - exception happen4
java.lang.Exception: exception happen4
at com.test.springbatch.RetryTest$1.doWithRetry(RetryTest.java:55)
at com.test.springbatch.RetryTest$1.doWithRetry(RetryTest.java:1)
at org.springframework.batch.retry.support.RetryTemplate.doExecute(RetryTemplate.java:240)
at org.springframework.batch.retry.support.RetryTemplate.execute(RetryTemplate.java:147)
at com.test.springbatch.RetryTest.main(RetryTest.java:46)
INFO [com.test.springbatch.RetryTest] - 失敗
第4次發生了異常之後,馬上就把異常拋給了我們自己定義的異常處理。
代碼級的重試給了我們很高的靈活度,把某些比較容易出錯的代碼放入其中,能很好的增強我們代碼的健壯性。