SimpleDateFormat高并发下异常java.lang.NumberFormatException: For input string: ""
SimpleDateFormat高并发下异常java.lang.NumberFormatException: For input string: ""
1. 原因
SimpleDateFormat(下面简称sdf)类内部有一个Calendar对象引用,它用来储存和这个sdf相关的日期信息,例如sdf.parse(dateStr), sdf.format(date) 诸如此类的方法参数传入的日期相关String, Date等等, 都是交友Calendar引用来储存的.这样就会导致一个问题,如果你的sdf是个static的, 那么多个thread 之间就会共享这个sdf, 同时也是共享这个Calendar引用,
java.lang.NumberFormatException: For input string: ""
at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)
测试
public static void main(String[] args) throws InterruptedException {
ExecutorService executorService = Executors.newFixedThreadPool(500);
for (int i = 0; i < 500; i++) {
executorService.execute(new Runnable() {
@Override
public void run() {
for (int i = 0; i < 1000000; i++) {
Date parse = null;
try {
// boolean ff =
// DataFormatUtils.compareDate2AaaconfigTimeformat(System.currentTimeMillis(),
// "2014-01-01 00:00:00");
parse = DataFormatUtils.yyyy_MM_dd_HH_mm_ss.parse("2014-01-01 00:00:00");
// DateUtil.parse("2014-01-01 00:00:00","yyyy-MM-dd HH:mm:ss" );
// System.out.println(parse);
} catch (Exception e) {
e.printStackTrace();
System.out.println(e);
System.out.println(parse);
}
}
}
});
}
Thread.sleep(3000000);
}
解决1
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.HashMap;
import java.util.Map;
/**
* @author zhenwei.liu created on 2013 13-8-29 下午5:35
* @version $Id$
*/
public class DateUtil {
/** 锁对象 */
private static final Object lockObj = new Object();
/** 存放不同的日期模板格式的sdf的Map */
private static Map<String, ThreadLocal<SimpleDateFormat>> sdfMap = new HashMap<String, ThreadLocal<SimpleDateFormat>>();
/**
* 返回一个ThreadLocal的sdf,每个线程只会new一次sdf
*
* @param pattern
* @return
*/
private static SimpleDateFormat getSdf(final String pattern) {
ThreadLocal<SimpleDateFormat> tl = sdfMap.get(pattern);
// 此处的双重判断和同步是为了防止sdfMap这个单例被多次put重复的sdf
if (tl == null) {
synchronized (lockObj) {
tl = sdfMap.get(pattern);
if (tl == null) {
// 只有Map中还没有这个pattern的sdf才会生成新的sdf并放入map
System.out.println("put new sdf of pattern " + pattern + " to map");
// 这里是关键,使用ThreadLocal<SimpleDateFormat>替代原来直接new SimpleDateFormat
tl = new ThreadLocal<SimpleDateFormat>() {
@Override
protected SimpleDateFormat initialValue() {
System.out.println("thread: " + Thread.currentThread() + " init pattern: " + pattern);
return new SimpleDateFormat(pattern);
}
};
sdfMap.put(pattern, tl);
}
}
}
return tl.get();
}
/**
* 是用ThreadLocal<SimpleDateFormat>来获取SimpleDateFormat,这样每个线程只会有一个SimpleDateFormat
*
* @param date
* @param pattern
* @return
*/
public static String format(Date date, String pattern) {
return getSdf(pattern).format(date);
}
public static Date parse(String dateStr, String pattern) throws ParseException {
return getSdf(pattern).parse(dateStr);
}
}
解决2
package com.utstar.sxag.utils;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
public class DataFormatUtils {
private static final Logger LOG = LoggerFactory.getLogger(DataFormatUtils.class.getName());
/** 锁对象 */
private static final Object lockObj = new Object();
/** 存放不同的日期模板格式的sdf的Map */
private static Map<String, ThreadLocal<SimpleDateFormat>> sdfMap = new HashMap<String, ThreadLocal<SimpleDateFormat>>();
public static String configTimeFormat = "yyyy-MM-dd HH:mm:ss";
// 此种方式会有线程安全问题
// public static SimpleDateFormat yyyyMMdd = new SimpleDateFormat("yyyyMMdd");
// public static SimpleDateFormat yyyyMMddHHmmss = new
// SimpleDateFormat("yyyyMMddHHmmss");
// public static SimpleDateFormat yyyy_MM_dd_HH_mm_ss = new
// SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
// public static SimpleDateFormat aaaConfigTimeformat = new
// SimpleDateFormat(configTimeFormat);
public static SimpleDateFormat yyyyMMdd() {
return getSimpleDateFormat("yyyyMMdd");
}
public static SimpleDateFormat yyyyMMddHHmmss() {
return getSimpleDateFormat("yyyyMMddHHmmss");
}
public static SimpleDateFormat yyyy_MM_dd_HH_mm_ss() {
return getSimpleDateFormat("yyyy-MM-dd HH:mm:ss");
}
public static SimpleDateFormat aaaConfigTimeformat() {
return getSimpleDateFormat(configTimeFormat);
}
/**
* 返回一个ThreadLocal的getSimpleDateFormat,每个线程只会new一次getSimpleDateFormat
*
* @param pattern
* @return
*/
public static SimpleDateFormat getSimpleDateFormat(final String pattern) {
ThreadLocal<SimpleDateFormat> tl = sdfMap.get(pattern);
// 此处的双重判断和同步是为了防止sdfMap这个单例被多次put重复的sdf
if (tl == null) {
synchronized (lockObj) {
tl = sdfMap.get(pattern);
if (tl == null) {
// 只有Map中还没有这个pattern的sdf才会生成新的sdf并放入map
// System.out.println("put new sdf of pattern " + pattern + " to map");
// 这里是关键,使用ThreadLocal<SimpleDateFormat>替代原来直接new SimpleDateFormat
tl = new ThreadLocal<SimpleDateFormat>() {
@Override
protected SimpleDateFormat initialValue() {
// System.out.println("thread: " + Thread.currentThread() + " init pattern: " +
// pattern);
return new SimpleDateFormat(pattern);
}
};
sdfMap.put(pattern, tl);
}
}
}
return tl.get();
}
public static String yyyy_MM_dd_HH_mm_ss_2_yyyyMMddHHmmss(String data) throws ParseException {
LOG.info("DataFormatUtils data is " + data);
try {
Date newdata = yyyy_MM_dd_HH_mm_ss().parse(data);
return yyyyMMddHHmmss().format(newdata);
} catch (Exception e) {
LOG.info("DataFormatUtils parse date exception data is " + data);
return "";
}
}
public static String getCurrentTime_yyyyMMddHHmmss() {
return DataFormatUtils.yyyyMMddHHmmss().format(new Date());
}
public static String getCurrentTime_aaaConfigTimeFormat() {
return DataFormatUtils.aaaConfigTimeformat().format(new Date());
}
public static boolean compareExpriedtimeDate(long now, String expriedtime) {
return compareDate(now, expriedtime, yyyyMMddHHmmss());
}
public static boolean compareDate2AaaconfigTimeformat(long date1, String date2) {
return compareDate(date1, date2, aaaConfigTimeformat());
}
public static boolean compareDate(long date1, String date2, SimpleDateFormat simpleDateFormat) {
// LOG.info("DataFormatUtils compareDate datea is [" + date1 + "] date2 is [" +
// date2 + "] describe is [" + describe + "]");
if (!StringUtils.notNullEmpty(date2)) {
LOG.info("DataFormatUtils compareDate exception date2 is null or empty");
} else {
try {
if (date1 > simpleDateFormat.parse(date2).getTime()) {
return true;
}
} catch (Exception e) {
LOG.error("DataFormatUtils compareDate exception datea is [" + date1 + "] date2 is [" + date2 + "]", e);
}
}
return false;
}
public static String transDate(String date) {
if (!StringUtils.notNullEmpty(date)) {
return "";
}
try {
return yyyyMMddHHmmss().format(aaaConfigTimeformat().parse(date));
} catch (Exception e) {
LOG.error("DataFormatUtils transDate exception datea is [" + date + "]", e);
}
return "";
}
public static String transDate2(String date) {
try {
String dateStr = yyyyMMddHHmmss().format(yyyy_MM_dd_HH_mm_ss().parse(date));
return dateStr;
} catch (ParseException e) {
LOG.error("DataFormatUtils data format error date is[" + date + "]", e);
}
return "";
}
// 当前时间
public static String getCreatedate() {
return aaaConfigTimeformat().format(new Date());
}
// 当前时间index天后的日期
public static String getExpiredate(int index) {
// String DATE_TIME_FORMAT = "yyyy/MM/dd HH:mm:ss";
Calendar calendar = Calendar.getInstance();
calendar.add(Calendar.DATE, index);
return aaaConfigTimeformat().format(calendar.getTime());
}
// 当前时间index天后的日期
public static long getLongExpiredate(int day) {
return day * 24 * 60 * 60;
}
// 下index个月一号
public static String getActivedate(int index) {
Calendar calendar = Calendar.getInstance();
calendar.set(Calendar.DAY_OF_MONTH, 1);
calendar.add(Calendar.MONTH, index);
return aaaConfigTimeformat().format(calendar.getTime());
}
// 下index个月一号00:00:01
public static String getMonthlyZeroTime(int index) {
Calendar calendar = Calendar.getInstance();
calendar.set(Calendar.DAY_OF_MONTH, 1);
calendar.add(Calendar.MONTH, index);
String next_month = aaaConfigTimeformat().format(calendar.getTime());
return next_month.substring(0, 10) + " 00:00:00";
}
// 当前时间index小时后的日期
public static String getRentdate(int hour) {
Calendar calendar = Calendar.getInstance();
calendar.add(Calendar.HOUR, hour);
return aaaConfigTimeformat().format(calendar.getTime());
}
public static String getTransTime(String date) throws ParseException {
String s = "";
if (StringUtils.notNullEmpty(date)) {
try {
s = yyyyMMddHHmmss().format(DataFormatUtils.aaaConfigTimeformat().parse(date));
} catch (Exception e) {
LOG.error("DataFormatUtils instantSubscribe getTransTime exception date is " + date, e);
}
}
return s;
}
public static long getTimeDifference(String date) {
if (StringUtils.notNullEmpty(date)) {
Date otherDate = null;
try {
otherDate = yyyyMMddHHmmss().parse(date);
long s = otherDate.getTime() - System.currentTimeMillis();
if (s <= 0) {
return 60000;// 如果是负数过期时间就设置为60s
} else {
return s;
}
} catch (ParseException e) {
return -1;
}
}
return -1;
}
public static void main(String[] args) throws InterruptedException {
ExecutorService executorService = Executors.newFixedThreadPool(500);
for (int i = 0; i < 500; i++) {
executorService.execute(new Runnable() {
@Override
public void run() {
for (int i = 0; i < 1000000; i++) {
Date parse = null;
try {
// boolean ff =
// DataFormatUtils.compareDate2AaaconfigTimeformat(System.currentTimeMillis(),
// "2014-01-01 00:00:00");
parse = DataFormatUtils.yyyy_MM_dd_HH_mm_ss().parse("2014-01-01 00:00:00");
// DateUtil.parse("2014-01-01 00:00:00","yyyy-MM-dd HH:mm:ss" );
// System.out.println(parse);
} catch (Exception e) {
e.printStackTrace();
System.out.println(e);
System.out.println(parse);
}
}
}
});
}
Thread.sleep(3000000);
}
}
1. 原因
SimpleDateFormat(下面简称sdf)类内部有一个Calendar对象引用,它用来储存和这个sdf相关的日期信息,例如sdf.parse(dateStr), sdf.format(date) 诸如此类的方法参数传入的日期相关String, Date等等, 都是交友Calendar引用来储存的.这样就会导致一个问题,如果你的sdf是个static的, 那么多个thread 之间就会共享这个sdf, 同时也是共享这个Calendar引用, 并且, 观察 sdf.parse() 方法,你会发现有如下的调用:
Date parse() {
calendar.clear(); // 清理calendar
... // 执行一些操作, 设置 calendar 的日期什么的
calendar.getTime(); // 获取calendar的时间
}
这里会导致的问题就是, 如果 线程A 调用了 sdf.parse(), 并且进行了 calendar.clear()后还未执行calendar.getTime()的时候,线程B又调用了sdf.parse(), 这时候线程B也执行了sdf.clear()方法, 这样就导致线程A的的calendar数据被清空了(实际上A,B的同时被清空了). 又或者当 A 执行了calendar.clear() 后被挂起, 这时候B 开始调用sdf.parse()并顺利i结束, 这样 A 的 calendar内存储的的date 变成了后来B设置的calendar的date
2. 问题重现
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
/**
* @author zhenwei.liu created on 2013 13-8-29 下午5:35
* @version $Id$
*/
public class DateFormatTest extends Thread {
private static SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
private String name;
private String dateStr;
private boolean sleep;
public DateFormatTest(String name, String dateStr, boolean sleep) {
this.name = name;
this.dateStr = dateStr;
this.sleep = sleep;
}
@Override
public void run() {
Date date = null;
if (sleep) {
try {
TimeUnit.MILLISECONDS.sleep(2000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
try {
date = sdf.parse(dateStr);
} catch (ParseException e) {
e.printStackTrace();
}
System.out.println(name + " : date: " + date);
}
public static void main(String[] args) throws InterruptedException {
ExecutorService executor = Executors.newCachedThreadPool();
// A 会sleep 2s 后开始执行sdf.parse()
executor.execute(new DateFormatTest("A", "1991-09-13", true));
// B 打了断点,会卡在方法中间
executor.execute(new DateFormatTest("B", "2013-09-13", false));
executor.shutdown();
}
}
使用Debug模式执行这段代码,并在sdf.parse()方法里打上断点
parse() {
calendar.clear()
// 这里打一个断点
calendar.getTime()
}
过程:
1) 首先A线程跑起来以后会进入sleep
2) B线程跑起来, 卡在断点处
3) A线程醒过来, 执行 calendar.clear(), 并将设置sdf.calendar的date为1991-09-13, 此时 A B 的 calendar 都为 1991-09-13
4) 让断点继续执行, 输出如下
A : date: Fri Sep 13 00:00:00 CDT 1991
B : date: Fri Sep 13 00:00:00 CDT 1991
这并不是我们期待的结果
3. 解决方案
最简单的解决方案我们可以把static去掉,这样每个新的线程都会有一个自己的sdf实例,从而避免线程安全的问题
然而,使用这种方法,在高并发的情况下会大量的new sdf以及销毁sdf,这样是非常耗费资源的
在并发情况下,网站的请求任务与线程执行情况大概可以理解为如下
例如Tomcat的线程池的最大Thread数为4, 现在需要执行的任务有1000个(理解为有1000个用户点了你的网站的某个功能),
而这1000个任务都会用到我们写的日期函数处理类
A) 假如说日期函数处理类使用的是new SimpleDateFormat的方法,那么这里就会有1000次sdf的创建和销毁
B) Java中提供了一种ThreadLocal的解决方案,它的工作方式是,每个线程只会有一个实例,也就是说我们执行完这1000个任务,总共只会实例化4个sdf.
而且,它并不会有多线程的并发问题,因为,单个线程执行任务肯定是顺序的,例如Thread #1负责执行Task #1-#250, 那么他是顺序而执行Task #1-#250
而Thread #2拥有自己的sdf实例,他也是顺序执行任务 Task #251-#500, 以此类推
下面是一个使用ThreadLocal解决sdf多线程问题的例子
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.HashMap;
import java.util.Map;
/**
* @author zhenwei.liu created on 2013 13-8-29 下午5:35
* @version $Id$
*/
public class DateUtil {
/** 锁对象 */
private static final Object lockObj = new Object();
/** 存放不同的日期模板格式的sdf的Map */
private static Map<String, ThreadLocal<SimpleDateFormat>> sdfMap = new HashMap<String, ThreadLocal<SimpleDateFormat>>();
/**
* 返回一个ThreadLocal的sdf,每个线程只会new一次sdf
*
* @param pattern
* @return
*/
private static SimpleDateFormat getSdf(final String pattern) {
ThreadLocal<SimpleDateFormat> tl = sdfMap.get(pattern);
// 此处的双重判断和同步是为了防止sdfMap这个单例被多次put重复的sdf
if (tl == null) {
synchronized (lockObj) {
tl = sdfMap.get(pattern);
if (tl == null) {
// 只有Map中还没有这个pattern的sdf才会生成新的sdf并放入map
System.out.println("put new sdf of pattern " + pattern + " to map");
// 这里是关键,使用ThreadLocal<SimpleDateFormat>替代原来直接new SimpleDateFormat
tl = new ThreadLocal<SimpleDateFormat>() {
@Override
protected SimpleDateFormat initialValue() {
System.out.println("thread: " + Thread.currentThread() + " init pattern: " + pattern);
return new SimpleDateFormat(pattern);
}
};
sdfMap.put(pattern, tl);
}
}
}
return tl.get();
}
/**
* 是用ThreadLocal<SimpleDateFormat>来获取SimpleDateFormat,这样每个线程只会有一个SimpleDateFormat
*
* @param date
* @param pattern
* @return
*/
public static String format(Date date, String pattern) {
return getSdf(pattern).format(date);
}
public static Date parse(String dateStr, String pattern) throws ParseException {
return getSdf(pattern).parse(dateStr);
}
}
测试类
import java.text.ParseException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
/**
* @author zhenyu.nie created on 2013 13-8-26 下午2:13
* @version 1.0.0
*/
public class Test {
public static void main(String[] args) {
final String patten1 = "yyyy-MM-dd";
final String patten2 = "yyyy-MM";
Thread t1 = new Thread() {
@Override
public void run() {
try {
DateUtil.parse("1992-09-13", patten1);
} catch (ParseException e) {
e.printStackTrace();
}
}
};
Thread t2 = new Thread() {
@Override
public void run() {
try {
DateUtil.parse("2000-09", patten2);
} catch (ParseException e) {
e.printStackTrace();
}
}
};
Thread t3 = new Thread() {
@Override
public void run() {
try {
DateUtil.parse("1992-09-13", patten1);
} catch (ParseException e) {
e.printStackTrace();
}
}
};
Thread t4 = new Thread() {
@Override
public void run() {
try {
DateUtil.parse("2000-09", patten2);
} catch (ParseException e) {
e.printStackTrace();
}
}
};
Thread t5 = new Thread() {
@Override
public void run() {
try {
DateUtil.parse("2000-09-13", patten1);
} catch (ParseException e) {
e.printStackTrace();
}
}
};
Thread t6 = new Thread() {
@Override
public void run() {
try {
DateUtil.parse("2000-09", patten2);
} catch (ParseException e) {
e.printStackTrace();
}
}
};
System.out.println("单线程执行: ");
ExecutorService exec = Executors.newFixedThreadPool(1);
exec.execute(t1);
exec.execute(t2);
exec.execute(t3);
exec.execute(t4);
exec.execute(t5);
exec.execute(t6);
exec.shutdown();
sleep(1000);
System.out.println("双线程执行: ");
ExecutorService exec2 = Executors.newFixedThreadPool(2);
exec2.execute(t1);
exec2.execute(t2);
exec2.execute(t3);
exec2.execute(t4);
exec2.execute(t5);
exec2.execute(t6);
exec2.shutdown();
}
private static void sleep(long millSec) {
try {
TimeUnit.MILLISECONDS.sleep(millSec);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
输出
单线程执行:
put new sdf of pattern yyyy-MM-dd to map
thread: Thread[pool-1-thread-1,5,main] init pattern: yyyy-MM-dd
put new sdf of pattern yyyy-MM to map
thread: Thread[pool-1-thread-1,5,main] init pattern: yyyy-MM
双线程执行:
thread: Thread[pool-2-thread-1,5,main] init pattern: yyyy-MM-dd
thread: Thread[pool-2-thread-2,5,main] init pattern: yyyy-MM
thread: Thread[pool-2-thread-1,5,main] init pattern: yyyy-MM
thread: Thread[pool-2-thread-2,5,main] init pattern: yyyy-MM-dd
从输出我们可以看出:
1) 1个线程执行这6个任务的时候,这个线程首次使用过的时候会new一个新的sdf,并且以后都一直用这个sdf,而不是每次处理任务都新建一个新的sdf
2) 2个线程执行6个任务的时候也是同理,但是2个线程的sdf是分开的,每个线程都有自己的"yyyy-MM-dd", "yyyy-MM"的sdf,所以他们不会有线程安全安全问题
试想,如果使用的是new的实现方法,那么不管是用1个线程去执行,还是用2个线程去执行这6个任务,都需要new 6个sdf