我需要一个Java代码来根据用户输入创建一个cron表达式。 用户输入是时间，频率和执行次数。
答案 0 :(得分：13)
只需添加自己创建的评论。
以下是一个示例：提示用户输入值并将其传递给以下方法，Javadoc解释了允许哪个值（取自http://en.wikipedia.org/wiki/Cron#Format）。
这是未经测试的，不会验证任何输入字符串，但我相信你可以这样做。
/**
* Generate a CRON expression is a string comprising 6 or 7 fields separated by white space.
*
* @param seconds mandatory = yes. allowed values = {@code 0-59 * / , -}
* @param minutes mandatory = yes. allowed values = {@code 0-59 * / , -}
* @param hours mandatory = yes. allowed values = {@code 0-23 * / , -}
* @param dayOfMonth mandatory = yes. allowed values = {@code 1-31 * / , - ? L W}
* @param month mandatory = yes. allowed values = {@code 1-12 or JAN-DEC * / , -}
* @param dayOfWeek mandatory = yes. allowed values = {@code 0-6 or SUN-SAT * / , - ? L #}
* @param year mandatory = no. allowed values = {@code 1970–2099 * / , -}
* @return a CRON Formatted String.
*/
private static String generateCronExpression(final String seconds, final String minutes, final String hours,
final String dayOfMonth,
final String month, final String dayOfWeek, final String year)
{
return String.format("%1$s %2$s %3$s %4$s %5$s %6$s %7$s", seconds, minutes, hours, dayOfMonth, month, dayOfWeek, year);
}
Cron格式信息取自此处：http://en.wikipedia.org/wiki/Cron#Format
答案 1 :(得分：4)
您可以根据需要更改以下实施方案。
import java.io.Serializable;
public class CronExpressionCreator implements Serializable {
private static final long serialVersionUID = -1676663054009319677L;
public static void main(String[] args) {
CronExpressionCreator pCron = new CronExpressionCreator();
pCron.setTime("12:00 PM");
pCron.setMON(true);
pCron.setStartDate("12-05-2011");
System.out.println(pCron.getCronExpression());
}
public String getCronExpression() {
String time = getTime();
String[] time1 = time.split("\\:");
String[] time2 = time1[1].split("\\ ");
String hour = "";
if (time2[1].equalsIgnoreCase("PM")) {
Integer hourInt = Integer.parseInt(time1[0]) + 12;
if (hourInt == 24) {
hourInt = 0;
}
hour = hourInt.toString();
} else {
hour = time1[0];
}
String minutes = time2[0];
String cronExp = "";
if (isRecurring()) {
String daysString = "";
StringBuilder sb = new StringBuilder(800);
boolean moreConditions = false;
if (isSUN()) {
sb.append("SUN");
moreConditions = true;
}
if (isMON()) {
if (moreConditions) {
sb.append(",");
}
sb.append("MON");
moreConditions = true;
}
if (isTUE()) {
if (moreConditions) {
sb.append(",");
}
sb.append("TUE");
moreConditions = true;
}
if (isWED()) {
if (moreConditions) {
sb.append(",");
}
sb.append("WED");
moreConditions = true;
}
if (isTHU()) {
if (moreConditions) {
sb.append(",");
}
sb.append("THU");
moreConditions = true;
}
if (isFRI()) {
if (moreConditions) {
sb.append(",");
}
sb.append("FRI");
moreConditions = true;
}
if (isSAT()) {
if (moreConditions) {
sb.append(",");
}
sb.append("SAT");
moreConditions = true;
}
daysString = sb.toString();
cronExp = "0 " + minutes + " " + hour + " ? * " + daysString;
} else {
String startDate = getStartDate();
String[] dateArray = startDate.split("\\-");
String day = dateArray[0];
if (day.charAt(0) == '0') {
day = day.substring(1);
}
String month = dateArray[1];
if (month.charAt(0) == '0') {
month = month.substring(1);
}
String year = dateArray[2];
cronExp = "0 " + minutes + " " + hour + " " + day + " " + month
+ " ? " + year;
}
return cronExp;
}
String startDate;
String time;
boolean recurring;
boolean SUN;
boolean MON;
boolean TUE;
boolean WED;
boolean THU;
boolean FRI;
boolean SAT;
/**
* @return the startDate
*/
public String getStartDate() {
return startDate;
}
/**
* The date set should be of the format (MM-DD-YYYY for example 25-04-2011)
*
* @param startDate
* the startDate to set
*/
public void setStartDate(String startDate) {
this.startDate = startDate;
}
/**
* @return the time
*/
public String getTime() {
return time;
}
/**
* The time set should be of the format (HH:MM AM/PM for example 12:15 PM)
*
* @param time
* the time to set
*/
public void setTime(String time) {
this.time = time;
}
public boolean isRecurring() {
return recurring;
}
public void setRecurring(boolean recurring) {
this.recurring = recurring;
}
public boolean isSUN() {
return SUN;
}
public void setSUN(boolean sUN) {
SUN = sUN;
}
public boolean isMON() {
return MON;
}
/**
* @param mON
* the mON to set
*/
public void setMON(boolean mON) {
MON = mON;
}
public boolean isTUE() {
return TUE;
}
public void setTUE(boolean tUE) {
TUE = tUE;
}
public boolean isWED() {
return WED;
}
public void setWED(boolean wED) {
WED = wED;
}
public boolean isTHU() {
return THU;
}
public void setTHU(boolean tHU) {
THU = tHU;
}
public boolean isFRI() {
return FRI;
}
public void setFRI(boolean fRI) {
FRI = fRI;
}
public boolean isSAT() {
return SAT;
}
public void setSAT(boolean sAT) {
SAT = sAT;
}
public int hashCode() {
return this.getCronExpression().hashCode();
}
public boolean equals(Object obj) {
if (obj == null) {
return false;
}
if (obj instanceof CronExpressionCreator) {
if (((CronExpressionCreator) obj).getCronExpression()
.equalsIgnoreCase(this.getCronExpression())) {
return true;
}
} else {
return false;
}
return false;
}
}
答案 2 :(得分：4)
我认为你可以使用cron-utils，它带来了一个CronBuilder类并允许导出为多种格式。该功能从4.0.0版开始提供。
自述文件的一个例子：
//Create a cron expression. CronMigrator will ensure you remain cron provider agnostic
import static com.cronutils.model.field.expression.FieldExpressionFactory.*;
Cron cron = CronBuilder.cron(CronDefinitionBuilder.instanceDefinitionFor(CronType.QUARTZ))
.withYear(always())
.withDoM(between(1, 3))
.withMonth(always())
.withDoW(questionMark())
.withHour(always())
.withMinute(always())
.withSecond(on(0))
.instance();
//Obtain the string expression
String cronAsString = cron.asString();//0 * * 1-3 * ? *
//Migrate to Unix format
cron = CronMapper.fromQuartzToUnix().map(cron);
cronAsString = cron.asString();//* * 1-3 * *
答案 3 :(得分：3)
The snippet submitted by edwardsmatt above与Quartz的CronExpression无法正常工作。这是一个更正版本：
/**
* Generate a CRON expression is a string comprising 6 or 7 fields separated by white space.
*
* @param seconds mandatory = yes. allowed values = {@code 0-59 * / , -}
* @param minutes mandatory = yes. allowed values = {@code 0-59 * / , -}
* @param hours mandatory = yes. allowed values = {@code 0-23 * / , -}
* @param dayOfMonth mandatory = yes. allowed values = {@code 1-31 * / , - ? L W}
* @param month mandatory = yes. allowed values = {@code 1-12 or JAN-DEC * / , -}
* @param dayOfWeek mandatory = yes. allowed values = {@code 0-6 or SUN-SAT * / , - ? L #}
* @param year mandatory = no. allowed values = {@code 1970–2099 * / , -}
* @return a CRON Formatted String.
*/
private static String generateCronExpression(final String seconds, final String minutes, final String hours,
final String dayOfMonth,
final String month, final String dayOfWeek, final String year)
{
return String.format("%1$s %2$s %3$s %4$s %5$s %6$s %7$s", seconds, minutes, hours, dayOfMonth, month, dayOfWeek, year);
}