假设我有一个Java GUI,它在面板中显示40个来自所选区域的批处理对象,可以从A到Z.
从数据库中查询40个Batch对象,按区域缓存它们,以便每次对区域的每个请求都不涉及数据库。
public class BatchView
{
private int drawIt(Graphics g, String zone)
{
for(int i = 0; i<40; i++)
{
Batch tmpBatch = BatchDAO.getBatch(zone, i);
//draw the tmpBatch object
}
}
}
public class BatchDAO
{
public static MyCache cache = new MyCache(5000);
public getAllBatches(String zone)
{
ArrayList<Batch> batchArrayList = cache.get("batch-" + zone);
if(batchArrayList == null)
{
BuildBatchSwingWorker buildBatchSwingWorker = new BuildBatchSwingWorker(zone);
buildBatchSwingWorker.execute();
}
return batchList;
}
public Batch getBatch(String zone, int id)
{
//here I don't query database but exploit the cache
ArrayList<Batch> batchArrayList = getAllBatches(String zone);
for(int i = 0; i< batchArrayList.size(); i++)
{
if(batchArrayList.get(i).getId() == i)
return batchArrayList.get(i);
}
//if batch is not found it means it hasn't loaded yet so I return null
return null;
}
}
假设使用一系列通知正确更新缓存,并且每次drawIt()方法正确更新时,如何进行更新,以便不会同时为同一区域多次调用BuildBatchSwingWorker?
答案 0 :(得分:1)
鉴于您的代码,我认为您真正关心的不是SwingWorker执行多少次,而是只执行一次数据库调用,然后使用BatchDAO
缓存。
你需要正确地分离责任,缓存维护是BatchDAO
类的工作,因此摇摆工作者与它无关:
public class BatchDAO {
...
public getAllBatches(String zone) {
ArrayList<Batch> batchArrayList = cache.get("batch-" + zone);
if(batchArrayList == null) {
// here goes database call not swing worker!
}
return batchList;
}
...
}
然后在GUI类中执行swing worker(它所属的位置):
public class BatchView {
private int drawIt(Graphics g, String zone) {
SwingWorker<Void, Batch> worker = new SwingWorker<Void, Batch>() {
@Override
protected Void doInBackground() throws Exception {
for(int i = 0; i<40; i++) {
Batch tmpBatch = BatchDAO.getBatch(zone, i);
publish(tmpBatch);
}
return null;
}
@Override
protected void process(List<Batch> batches) {
for(Batch batch : batches) {
//draw the batch object
}
}
};
worker.execute();
}
}
注意如果cache.get("batch-" + zone) == null
那么数据库调用只执行一次,但如果没有,那么你将使用你的chache并且doInBackground()
方法将在眨眼间执行,我认为是你的目标。
由于我在BatchView
课程中看到了Graphics个参数作为参数。构造函数,我建议你仔细阅读Performing Custom Painting教程,以避免自定义绘制不需要的问题(当然,如果你还没有读过它)。
答案 1 :(得分:0)
这是你可以调用的Swing实用程序的一个很好的例子:)
/*
* To change this template, choose Tools | Templates
* and open the template in the editor.
package com.verve.swinguti;
import javax.swing.SwingUtilities;
/**
*
* @author kishan
*/
public class Utilities extends javax.swing.JFrame {
/**
* Creates new form Utilities
*/
public Utilities() {
initComponents();
}
/**
* This method is called from within the constructor to initialize the form.
* WARNING: Do NOT modify this code. The content of this method is always
* regenerated by the Form Editor.
*/
@SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">
private void initComponents() {
jPanel1 = new javax.swing.JPanel();
jButton2 = new javax.swing.JButton();
jButton1 = new javax.swing.JButton();
setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
jButton2.setText("jButton2");
jButton2.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
jButton2ActionPerformed(evt);
}
});
javax.swing.GroupLayout jPanel1Layout = new javax.swing.GroupLayout(jPanel1);
jPanel1.setLayout(jPanel1Layout);
jPanel1Layout.setHorizontalGroup(
jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(jPanel1Layout.createSequentialGroup()
.addGap(71, 71, 71)
.addComponent(jButton2)
.addContainerGap(155, Short.MAX_VALUE))
);
jPanel1Layout.setVerticalGroup(
jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(jPanel1Layout.createSequentialGroup()
.addGap(118, 118, 118)
.addComponent(jButton2)
.addContainerGap(128, Short.MAX_VALUE))
);
jButton1.setText("jButton1");
jButton1.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
jButton1ActionPerformed(evt);
}
});
javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
getContentPane().setLayout(layout);
layout.setHorizontalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addContainerGap()
.addComponent(jButton1)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
.addComponent(jPanel1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
.addContainerGap())
);
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addContainerGap()
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addComponent(jButton1)
.addGap(0, 0, Short.MAX_VALUE))
.addComponent(jPanel1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
.addContainerGap())
);
pack();
}// </editor-fold>
private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {
// TODO add your handling code here:
try {
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
try {
for (int i = 0; i < 10; i++) {
System.out.println("This is Good Example**");
Thread.sleep(2000);
}
} catch (Exception e) {
e.printStackTrace();
}
}
});
} catch (Exception e) {
e.printStackTrace();
}
}
private void jButton2ActionPerformed(java.awt.event.ActionEvent evt) {
// TODO add your handling code here:
try {
System.out.println("This is Second Button");
} catch (Exception e) {
e.printStackTrace();
}
}
/**
* @param args the command line arguments
*/
public static void main(String args[]) {
/*
* Set the Nimbus look and feel
*/
//<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
/*
* If Nimbus (introduced in Java SE 6) is not available, stay with the
* default look and feel. For details see
* http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html
*/
try {
for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
if ("Nimbus".equals(info.getName())) {
javax.swing.UIManager.setLookAndFeel(info.getClassName());
break;
}
}
} catch (ClassNotFoundException ex) {
java.util.logging.Logger.getLogger(Utilities.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (InstantiationException ex) {
java.util.logging.Logger.getLogger(Utilities.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (IllegalAccessException ex) {
java.util.logging.Logger.getLogger(Utilities.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (javax.swing.UnsupportedLookAndFeelException ex) {
java.util.logging.Logger.getLogger(Utilities.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
}
//</editor-fold>
/*
* Create and display the form
*/
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
new Utilities().setVisible(true);
}
});
}
// Variables declaration - do not modify
private javax.swing.JButton jButton1;
private javax.swing.JButton jButton2;
private javax.swing.JPanel jPanel1;
// End of variables declaration
}