1. CREATE TABLE `test` (
2. `id` int(11) NOT NULL AUTO_INCREMENT,
3. PRIMARY KEY (`id`)
4. ) ENGINE=InnoDB DEFAULT CHARSET=utf8

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;public class SeqGenerator {private static ExecutorService singleThreadExecutor = Executors.newSingleThreadExecutor();private static int currentVal = -1;private static int maxVal = -1;private static int fetchSize = 10000;//每次生成一万个idstatic{try {fetchFromDB();} catch (Exception e) {// TODO Auto-generated catch block
            e.printStackTrace();}}public static int getSeq() throws InterruptedException, ExecutionException {Callable<Integer> c = new Callable<Integer>() {@Overridepublic Integer call() throws Exception {int result = currentVal;if (currentVal > maxVal) {//如果当前值>数据库最大值，重新生成idfetchFromDB();result = currentVal;}currentVal++;return result;}};Future<Integer> task = singleThreadExecutor.submit(c);return task.get().intValue();}private static void fetchFromDB() throws Exception {Class.forName("com.mysql.jdbc.Driver");Connection connection = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/test", "xx", "xx");connection.setAutoCommit(false);Statement st = connection.createStatement();ResultSet rs = st.executeQuery("select * from test for update");rs.next();currentVal = rs.getInt(1) + 1;//当前值rs.close();st.executeUpdate("update test set id=id+" + fetchSize);//更新db中最大值rs = st.executeQuery("select * from test for update");rs.next();maxVal = rs.getInt(1);//最大值connection.commit();rs.close();st.close();connection.close();}public static void main(String[] args) throws Exception {int i = 1000000;long start = System.currentTimeMillis();while (i > 0) {System.out.println(SeqGenerator.getSeq());i--;}long end = System.currentTimeMillis();System.out.println(end - start);}
}