namespace
{
// strand提供串行执行, 能够保证线程安全, 同时被post或dispatch的方法, 不会被并发的执行.
// io_service不能保证线程安全
boost::asio::io_service m_service;
boost::asio::strand m_strand(m_service);
boost::mutex m_mutex;
void print(int id)
{
// boost::mutex::scoped_lock lock(m_mutex);
static int count = 0;
PRINT_DEBUG("id: " << boost::lexical_cast<std::string>(id));
PRINT_DEBUG("count: " << boost::lexical_cast<std::string>(++count));
}
void ioRun1()
{
while(true)
{
m_service.run();
}
}
void ioRun2()
{
while(true)
{
m_service.run();
}
}
void strand_print1()
{
// PRINT_DEBUG("Enter print1");
m_strand.dispatch(boost::bind(print, 1));
// PRINT_DEBUG("Exit print1");
}
void strand_print2()
{
// PRINT_DEBUG("Enter print2");
m_strand.post(boost::bind(print, 2));
// PRINT_DEBUG("Exit print2");
}
void strand_print3()
{
// PRINT_DEBUG("Enter print3");
m_strand.post(boost::bind(print, 3));
// PRINT_DEBUG("Exit print3");
}
void strand_print4()
{
// PRINT_DEBUG("Enter print4");
m_strand.post(boost::bind(print, 4));
// PRINT_DEBUG("Exit print4");
}
// 将上面的m_strand换成m_service后，
void service_print1()
{
// PRINT_DEBUG("Enter print1");
m_service.dispatch(boost::bind(print, 1));
// PRINT_DEBUG("Exit print1");
}
void service_print2()
{
// PRINT_DEBUG("Enter print2");
m_service.post(boost::bind(print, 2));
// PRINT_DEBUG("Exit print2");
}
void service_print3()
{
// PRINT_DEBUG("Enter print3");
m_service.post(boost::bind(print, 3));
// PRINT_DEBUG("Exit print3");
}
void service_print4()
{
// PRINT_DEBUG("Enter print4");
m_service.post(boost::bind(print, 4));
// PRINT_DEBUG("Exit print4");
}
}
void test_strand()
{
boost::thread ios1(ioRun1);
boost::thread ios2(ioRun2);
boost::thread t1(strand_print1);
boost::thread t2(strand_print2);
boost::thread t3(strand_print3);
boost::thread t4(strand_print4);
t1.join();
t2.join();
t3.join();
t4.join();
m_service.run();
}
void test_service()
{
boost::thread ios1(ioRun1);
boost::thread ios2(ioRun2);
boost::thread t1(service_print1);
boost::thread t2(service_print2);
boost::thread t3(service_print3);
boost::thread t4(service_print4);
t1.join();
t2.join();
t3.join();
t4.join();
m_service.run();
}
test_strand的执行结果:2013-01-05 17:25:34 626 [8228] DEBUG - id: 4 2013-01-05 17:25:34 631 [8228] DEBUG - count: 1 2013-01-05 17:25:34 634 [5692] DEBUG - id: 1 2013-01-05 17:25:34 637 [5692] DEBUG - count: 2 2013-01-05 17:25:34 640 [5692] DEBUG - id: 2 2013-01-05 17:25:34 642 [5692] DEBUG - count: 3 2013-01-05 17:25:34 646 [5692] DEBUG - id: 3 2013-01-05 17:25:34 649 [5692] DEBUG - count: 4test_ioserivice的执行结果:
2013-01-05 17:26:28 071 [3236] DEBUG - id: 1 2013-01-05 17:26:28 071 [5768] DEBUG - id: 2 2013-01-05 17:26:28 071 [5108] DEBUG - id: 3 2013-01-05 17:26:28 076 [3236] DEBUG - count: 1 2013-01-05 17:26:28 079 [5768] DEBUG - count: 2 2013-01-05 17:26:28 083 [5108] DEBUG - count: 3 2013-01-05 17:26:28 087 [3236] DEBUG - id: 4 2013-01-05 17:26:28 099 [3236] DEBUG - count: 4从结果可以看到, 在test_strand中print中两个打印函数成对执行, 在test_ioservice两个打印函数就没有线程安全可言了.
如果要保证test_ioservice同步, 就要加上mutex, 在代码中被注释的那句.
1.为什么需要ModelDriven？
所谓ModelDriven，意思是直接把实体类当成页面数据的收集对象。比如，有实体类User如下：
package cn.com.leadfar.struts2.actions;
public class User {
private int id;
private String username;
private String password;
private int age;
private String address;
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
}
假如要写一个Action，用来添加User。
第一种做法是直接在Action中定义所有需要的属性，然后在JSP中直接用属性名称来提交数据：
UserAction:
public class UserAction {
private int id;
private String username;
private String password;
private int age;
private String address;
public String add(){
User user = new User();
user.setId(id);
user.setUsername(username);
user.setPassword(password);
user.setAge(age);
user.setAddress(address);
new UserManager().addUser(user);
return "success";
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
}
add_input.jsp:
<form action="test/user.action" method="post">
<input type="hidden" name="method:add">
username:<input type="text" name="username"> <br/>
password:<input type="text" name="password"> <br/>
age:<input type="text" name="age"> <br/>
address:<input type="text" name="address"> <br/>
<input type="submit" name="submit" value="添加用户">
</form> <br/>
上述做法不好之处是：如果实体类的属性非常多，那么Action中也要定义相同的属性。
第二种做法是将User对象定义到UserAction中，然后在JSP中通过user属性来给user赋值：
UserAction:
public class UserAction {
private User user;
public String add(){
new UserManager().addUser(user);
return "success";
}
public User getUser() {
return user;
}
public void setUser(User user) {
this.user = user;
}
}
add_input.jsp:
<form action="test/user.action" method="post">
<input type="hidden" name="method:add">
username:<input type="text" name="user.username"> <br/>
password:<input type="text" name="user.password"> <br/>
age:<input type="text" name="user.age"> <br/>
address:<input type="text" name="user.address"> <br/>
<input type="submit" name="submit" value="添加用户">
</form> <br/>
这种做法不好的地方是：JSP页面上表单域中的命名变得太长
第三种做法是利用ModelDriven机制，让UserAction实现一个ModelDriven接口，同时实现接口中的方法：getModel()。如下所示：
public class UserAction implements ModelDriven{
private User user;
@Override
public Object getModel() {
if(user == null){
user = new User();
}
return user;
}
public String add(){
new UserManager().addUser(user);
return "success";
}
public User getUser() {
return user;
}
public void setUser(User user) {
this.user = user;
}
}
JSP的代码如下：
<form action="test/user.action" method="post">
<input type="hidden" name="method:add">
username:<input type="text" name="username"> <br/>
password:<input type="text" name="password"> <br/>
age:<input type="text" name="age"> <br/>
<input type="submit" name="submit" value="添加用户">
</form> <br/>
可见，第三种做法是比较好的，Action和JSP写起来都比较简单。
2.ModelDriven背后的机制？
ModelDriven背后的机制就是ValueStack。界面通过：username/age/address这样的名称，就能够被直接赋值给user对象，这证明user对象正是ValueStack中的一个root对象！
那么，为什么user对象会在ValueStack中呢？它是什么时候被压入ValueStack的呢？答案是：ModelDrivenInterceptor（关于Interceptor的概念，请参考后续章节的说明）。ModelDrivenInterceptor是缺省的拦截器链的一部分，当一个请求经过ModelDrivenInterceptor的时候，在这个拦截器中，会判断当前要调用的Action对象是否实现了ModelDriven接口，如果实现了这个接口，则调用getModel()方法，并把返回值（本例是返回user对象）压入ValueStack。
请看ModelDrivenInterceptor的代码：
public class ModelDrivenInterceptor extends AbstractInterceptor {
protected boolean refreshModelBeforeResult = false;
public void setRefreshModelBeforeResult(boolean val) {
this.refreshModelBeforeResult =
<Window x:Class="WpfApp2.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:objs="clr-namespace:WpfApp2.Objects"
xmlns:col="clr-namespace:System.Collections;assembly=mscorlib"
xmlns:sys="clr-namespace:System;assembly=mscorlib"
Title="MainWindow" Height="300" Width="300">
<Window.Resources>
<col:ArrayList x:Key="ds">
<objs:Student Name="Timothy" Skill="WPF" HasJob="True" Id="1"/>
<objs:Student Name="Anders" Skill="C#" HasJob="True" Id="2"/>
<objs:Student Name="Tommy" Skill="ASP.NET" HasJob="True" Id="3"/>
<objs:Student Name="Jim" Skill="WCF" HasJob="True" Id="4"/>
<objs:Student Name="Andy" Skill="WF" HasJob="False" Id="5"/>
<objs:Student Name="Jack" Skill="JAVA" HasJob="True" Id="6"/>
</col:ArrayList>
<Style TargetType="{x:Type TextBlock}">
<Setter Property="Width" Value="60"/>
</Style>
<DataTemplate x:Key="nameDT" DataType="{x:Type objs:Student}">
<TextBox x:Name="textBoxName" Width="60" Text="{Binding Name}" GotFocus="textBoxName_GotFocus"/>
</DataTemplate>
<DataTemplate x:Key="skillDT">
<TextBox x:Name="textBoxSkill" Width="60" Text="{Binding Skill}"/>
</DataTemplate>
<DataTemplate x:Key="hasJobDT">
<CheckBox Width="60" IsChecked="{Binding HasJob}"/>
</DataTemplate>
</Window.Resources>
<StackPanel>
<ListView x:Name="lv" ItemsSource="{StaticResource ds}">
<ListView.View>
<GridView>
<GridViewColumn Header="ID" DisplayMemberBinding="{Binding Id}"/>
<GridViewColumn Header="姓名" CellTemplate="{StaticResource nameDT}"/>
<GridViewColumn Header="技术" CellTemplate="{StaticResource skillDT}"/>
<GridViewColumn Header="已工作" CellTemplate="{StaticResource hasJobDT}"/>
</GridView>
</ListView.View>
</ListView>
<Button Content="Find" Margin="5,5" Click="Button_Click" Width="80"/>
</StackPanel>
</Window>
private void textBoxName_GotFocus(object sender, RoutedEventArgs e)
{
TextBox tb = e.OriginalSource as TextBox;
ContentPresenter cp = tb.TemplatedParent as ContentPresenter;
Student stu = cp.Content as Student;
this.lv.SelectedItem = stu;
ListViewItem lvi = this.lv.ItemContainerGenerator.ContainerFromItem(stu) as ListViewItem;
CheckBox cb = FindVisualChild<CheckBox>(lvi);
MessageBox.Show(cb.IsChecked.ToString());
}
public ChildType FindVisualChild<ChildType>(DependencyObject obj)
where ChildType:DependencyObject
{
//借助VisualTreeHelper类获取子控件
for (int i = 0; i < VisualTreeHelper.GetChildrenCount(obj); i++)
{
DependencyObject child = VisualTreeHelper.GetChild(obj, i);
if (child != null && child is ChildType)
return child as ChildType;
else
{
ChildType childOfChild = FindVisualChild<ChildType>(child);
if (childOfChild != null)
return childOfChild;
}
}
return null;
}11.5 深入浅出话Style
构成Style最重要的两种元素是Setter和Trigger，Setter类帮助我们设置控件的静态外观风格，Trigger类则帮助我们设置控件的行为风格。
11.5.1 Style中的Setter
<Window x:Class="WpfApp3.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="350" Width="525">
<Window.Resources>
<Style TargetType="{x:Type TextBlock}">
<Setter Property="FontSize" Value="24"/>
<Setter Property="TextDecorations" Value="Underline"/>
<Setter Property="FontStyle" Value="Italic"/>
</Style>
</Window.Resources>
<Grid>
<StackPanel>
<TextBlock Text="Hello WPF!"/>
<TextBlock Text="This is a sample Style!"/>
<TextBlock Text="by Anders 1/5/13" Style="{x:Null}"/>
</StackPanel>
</Grid>
</Window>
11.5.2 Style中的Trigger
1. 基本Trigger
<Window x:Class="WpfApp3.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="350" Width="525">
<Window.Resources>
<Style TargetType="{x:Type CheckBox}">
<Style.Triggers>
<Trigger Property="IsChecked" Value="True">
<Setter Property="FontSize" Value="24"/>
<Setter Property="Foreground" Value="Orange"/>
</Trigger>
</Style.Triggers>
</Style>
</Window.Resources>
<Grid>
<StackPanel>
<CheckBox Content="月光宝盒" IsChecked="True"/>
<CheckBox Content="大话西游" IsChecked="False"/>
</StackPanel>
</Grid>
</Window>
2. MultiTrigger
MultiTrigger实际上叫MultiConditionTrigger更合适，因为必须多个条件同时成立时才会被触发。
<Window x:Class="WpfApp3.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="350" Width="525">
<Window.Resources>
<Style TargetType="{x:Type CheckBox}">
<Style.Triggers>
<MultiTrigger>
<MultiTrigger.Conditions>
<Condition Property="IsChecked" Value="True"/>
<Condition Property="Content" Value="大话西游"/>
</MultiTrigger.Conditions>
<Setter Property="FontSize" Value="24"/>
<Setter Property="Foreground" Value="Orange"/>
</MultiTrigger>
</Style.Triggers>
</Style>
</Window.Resources>
<Grid>
<StackPanel>
<CheckBox Content="月光宝盒" IsChecked="True"/>
<CheckBox Content="大话西游" IsChecked="True"/>
<CheckBox Content="大话西游" IsChecked="False"/>
<CheckBox Content="月光宝盒" IsChecked="True"/>
</StackPanel>
</Grid>
</Window>