这是我的第一篇文章，所以如果需要，请让我知道是否有任何我应该添加到帖子中的内容。
我有一个程序，它从我的 MySQL 数据库中获取 url，并将它们发送到一个类，该类会将图像下载到我的桌面。
我需要获取 80,000 张图像，而且我想利用多线程来加快速度。
我已经到了某个地方，但现在我被困住了，因为我是多线程的新手，所以我花了几个小时研究。
问题是当程序运行时，它会一遍又一遍地处理前 5 个条目。这恰好是 ExecutorFixedPoolSize。
有人能帮助我吗。
我的代码如下。
public static void main(String[] args) {
try{
countAllAltPicsNotSaved();
System.out.println("Not saved: " + totalAltPicsNotSaved);
Class.forName("com.mysql.jdbc.Driver");
Connection conn =DriverManager.getConnection(dbUrl + dbName, userName, password);
Statement s = conn.createStatement ();
s.executeQuery ("SELECT DISTINCT id from productsaltimages WHERE saved != 1");
ResultSet rs = s.getResultSet();
int saveCounter = 0, altImageCount = 0;
List<Thread> threads = new ArrayList<Thread>();
while (rs.next()) { //Get ID
altImageCount = 0; //Product Alt Image Counter
String id = rs.getString("id"); //Product Table ID
Statement news = conn.createStatement (); //New Conn for get Alt Images From ID
news.executeQuery ("SELECT url from productsaltimages WHERE id ='"+id+"' AND saved != 5"); //Gets query from mySQL
ResultSet newrs = news.getResultSet(); //Resultset for AltImges for ID
ExecutorService executor = Executors.newFixedThreadPool(5);
Runnable task = null;
while (newrs.next()){ //Get Images
altImageCount++; //Increment ID Alt Image Counter
String url = newrs.getString("url");
task = new DownloadImage(url, id, altImageCount);
executor.execute(task);
}
}
} catch (Exception e){
}
}
public static void countAllAltPicsNotSaved() throws Exception {
try{
totalAltPicsNotSaved=0;
Class.forName("com.mysql.jdbc.Driver");
Connection conn =DriverManager.getConnection(dbUrl + dbName, userName, password);
Statement s = conn.createStatement ();
boolean sqlExecuteok = false;
s.executeQuery ("SELECT * from productsaltimages WHERE saved = '0'");
ResultSet rs = s.getResultSet ();
while (rs.next()) {
totalAltPicsNotSaved++;
}
rs.close();
s.close();
conn.close();
} catch (Exception e){
}
}
For my DownloadImage class code is:
public class DownloadImage implements Runnable
{
String url, id, threadName;
private int altImageCount = 0;
private static String userName = "owner";
private static String password = "hello123";
private static String dbUrl = "jdbc:mysql://localhost/";
private static String dbName = "shop";
private static String dbClass = "com.mysql.jdbc.Driver";
public DownloadImage(String url, String id, int altImageCount)
{
this.url = url;
this.id = id;
this.altImageCount = altImageCount;
}
public void run()
{
while(true)
{
File file=new File("D:\\FBShop_AltImages\\" + id + "\\");
boolean exists = file.exists();
if (!exists) {
// Create multiple directories
boolean success = (new File("D:\\FBShop_AltImages\\" + id + "\\")).mkdirs();
}
String newFilename = "D:\\FBShop_AltImages\\" + id + "\\" + id + "_" + altImageCount + ".jpg";
try {
try {
BufferedImage image = null;
URL imgurl = new URL(url);
URLConnection con = imgurl.openConnection();
con.setConnectTimeout(50 * 10000);
con.setReadTimeout(50 * 10000);
InputStream in = con.getInputStream();
image = ImageIO.read(in);
ImageIO.write(image, "jpg", new File(newFilename));
} catch (Exception e) {
System.out.println("Error getting image: " + url);
}
try {
//UpdateTable
Class.forName("com.mysql.jdbc.Driver");
String updatesql = "UPDATE productsaltimages SET saved = '1' WHERE id = '"+id+"'";
Connection conn =DriverManager.getConnection(dbUrl + dbName, userName, password);
Statement ups = conn.createStatement ();
int val = ups.executeUpdate(updatesql);
System.out.println("Task Complete: " + url);
try {
Thread.sleep(5000);
} catch (Exception e) {
}
} catch (Exception e) {
}
} catch (Exception e) {
}
//System.out.println("Thread Finished: " + threadName);
}
}
}