Java的ExecutorService的实施协助 [英] Java ExecutorService Implementation Assistance

问题描述

在以下code，用户列表获取数据的高容量，由于其发送电子邮件需要很长的时间。

我怎样才能加快，使得50000电子邮件发送更快的应用程序？也许与使用的的ExecutorService ？

 列表＆LT;的String []＆GT;用户列表=新的ArrayList＆LT;的String []＆GT;（）;
无效getRecords（）{
    的String []道具= NULL;
    而（rs.next（））{
    道具=新的String [2];
    道具[0] = rs.getString（USEREMAIL）;
    道具[1] = rs.getString（活性）;
    userList.add（道具）;
    如果（userList.size（）＆0）sendEmail（）;
}
无效sendEmail（）{
    的String []用户= NULL;
    对于（INT K = 0; K＆LT; userList.size（）; K ++）{
        用户= userList.get（K）;
        USEREMAIL =用户[0];
        //发送电子邮件code
    }
}
 

解决方案

尝试并行化code在这样的方式：

 私人最终诠释THREADS_NUM = 20;无效sendEmail（）抛出InterruptedException的{
    ExecutorService的执行人= Executors.newFixedThreadPool（THREADS_NUM）;
    对于（字符串[]用户：用户列表）{
        最后弦乐USEREMAIL =用户[0];
        executor.submit（新的Runnable（）{
            @覆盖
            公共无效的run（）{
                sendMailTo（USEREMAIL）;
            }
        }）;
    }
    长超时= ...
    的TimeUnit TIMEUNIT = ...
    executor.shutdown（）;
    executor.awaitTermination（超时，TIMEUNIT）;
}无效sendMailTo（字符串USEREMAIL）{
// code发送电子邮件
}
 

此外，请注意，如果你不希望有一个头痛 - 方法 sendMailTo 必须是无状态

In the following code, userList gets high volume of data due to which sending email takes too long time.

How can I speed up the application such that 50000 emails are sent faster? Maybe with the use of an ExecutorService?

List<String[]> userList = new ArrayList<String[]>();
void getRecords() {
    String [] props=null;
    while (rs.next()) {
    props = new String[2];
    props[0] = rs.getString("useremail");
    props[1] = rs.getString("active");
    userList.add(props);
    if (userList.size()>0) sendEmail();   
}
void sendEmail() {
    String [] user=null;
    for (int k=0; k<userList.size(); k++) { 
        user = userList.get(k);
        userEmail = user[0];         
        //send email code
    }
}

解决方案

Try parallelize your code in such way:

private final int THREADS_NUM = 20;

void sendEmail() throws InterruptedException {
    ExecutorService executor = Executors.newFixedThreadPool( THREADS_NUM );
    for ( String[] user : userList ) { 
        final String userEmail = user[0];         
        executor.submit( new Runnable() {
            @Override
            public void run() {
                sendMailTo( userEmail );
            }
        } );
    }
    long timeout = ...
    TimeUnit timeunit = ...
    executor.shutdown();
    executor.awaitTermination( timeout, timeunit );
}

void sendMailTo( String userEmail ) {
// code for sending e-mail
}

Also, note, if you don't want to have a headache - method sendMailTo must be stateless.

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