假设我们有两个员工SunA和SunB。这里的员工有两个属性，分别为名称和等级。存在经理和员工的情况下,一个员工可以设置自己名字,但他不能设置另一个员工姓名,同样一个员工不能制定自己的年级,但他可以设置另一个员工的等级。
1.首先创建一个雇员类：Employee.java
package proxypattern;
public interface Employee {
public String getName();
public int getGrade();
public void setName(String aName);
public void setGrade(int aGrade);}
2. 实现Employee类里的方法
package proxypattern;
public class EmployeeImpl implements Employee {
private String gName;
private int gGrade;
public EmployeeImpl() {
}
@Override
public String getName() {
return gName;
}
@Override
public int getGrade() {
return gGrade;
}
@Override
public void setName(String aName) {
gName = aName;
}
@Override
public void setGrade(int aGrade) {
gGrade = aGrade;
}}
3. 接着创建两个InvocationHandler。Invocationhandler实现代理的行为。
public class FirstInvocationHandler implements InvocationHandler {
Employee gEmployee;
public FirstInvocationHandler(Employee aEmployee) {
gEmployee = aEmployee;
}
@Override
public Object invoke(Object proxy, Method method, Object[] args) throws IllegalAccessException {
try {
if (method.getName().startsWith("get")) {
return method.invoke(gEmployee, args);
} else if (method.getName().equals("setGrade")) {
throw new IllegalAccessException();
} else if (method.getName().startsWith("set")) {
return method.invoke(gEmployee, args);
}
} catch (InvocationTargetException aEx) {
aEx.printStackTrace();
}
return null;
}}
-------------------------------------------------------------
/**
* Created by pingL on 16/8/28.
*/
public class SecondInvocationHandler implements InvocationHandler {
Employee gEmployee;
public SecondInvocationHandler(Employee aEmployee) {
gEmployee = aEmployee;
}
@Override
public Object invoke(Object proxy, Method method, Object[] args) throws IllegalAccessException {
try {
if (method.getName().startsWith("get")){
return method.invoke(gEmployee,args);
}
else if (method.getName().equals("setName")){
throw new IllegalAccessException();
}
else if (method.getName().startsWith("set")) {
return method.invoke(gEmployee, args);
}
} catch (InvocationTargetException aEx) {
aEx.printStackTrace();
}
return null;
}}
4. 获取代理对象
Employee getFirstProxy(Employee aEmployee) {
return (Employee) Proxy.newProxyInstance(
aEmployee.getClass().getClassLoader(),
aEmployee.getClass().getInterfaces(),
new FirstInvocationHandler(aEmployee));
}
Employee getSecondProxy(Employee bEmployee) {
return (Employee) Proxy.newProxyInstance(
bEmployee.getClass().getClassLoader(),
bEmployee.getClass().getInterfaces(),
new SecondInvocationHandler(bEmployee));
}
< 上面有两个返回代理对象的方法,用于创建代理对象我们调用代理的静态方法newProxyInstance(),这需要作为参数,分别为类对象、类加载器、interfaces和invocationhandler。>
5. 创建一个员工数据库
public class EmployeeDB {
HashMap<String, Employee> theEmployeeDB = new HashMap<String, Employee>();
public EmployeeDB() {
}
public void addEmployee(Employee aEmployee) {
theEmployeeDB.put(aEmployee.getName(), aEmployee);
}
public Employee getEmployee(String aName) {
return theEmployeeDB.get(aName);
}}
6. 测试类进行验证
/**
* Created by pingL on 16/8/28.
*/
public class TestProxyPattern {
EmployeeDB employeeDB = new EmployeeDB();
public TestProxyPattern() {
Employee aEmp = new EmployeeImpl();
aEmp.setName("SunA");
aEmp.setGrade(1);
Employee bEmp = new EmployeeImpl();
bEmp.setName("SunB");
bEmp.setGrade(2);
employeeDB.addEmployee(aEmp);
employeeDB.addEmployee(bEmp);
}
Employee getFirstProxy(Employee aEmployee) {
return (Employee) Proxy.newProxyInstance(
aEmployee.getClass().getClassLoader(),
aEmployee.getClass().getInterfaces(),
new FirstInvocationHandler(aEmployee));
}
Employee getSecondProxy(Employee bEmployee) {
return (Employee) Proxy.newProxyInstance(
bEmployee.getClass().getClassLoader(),
bEmployee.getClass().getInterfaces(),
new SecondInvocationHandler(bEmployee));
}
public void runExample() {
Employee aFirstEmp = employeeDB.getEmployee("SunA");
Employee aFirstEmpProxy = getFirstProxy(aFirstEmp);
aFirstEmpProxy.setName("SunAChanged");
System.out.println("New name of SunA is >>" + aFirstEmp.getName());
try {
aFirstEmpProxy.setGrade(10);
} catch (Exception theEx) {
System.out.println(aFirstEmp.getName() + "You can't set your grade youself," +
". You grade is still :" + aFirstEmp.getGrade());
}
Employee aSecondEmp = employeeDB.getEmployee("SunB");
Employee aSecondEmpProxy = getSecondProxy(aFirstEmp);
aSecondEmpProxy.setGrade(5);
System.out.println(aFirstEmp.getName() + "You grade is changed by " +
aSecondEmp.getName() + ". You grade is now : " + aFirstEmp.getGrade());
try {
aSecondEmpProxy.setName("SunA_changed_by_SunB");
} catch (Exception theEx) {
System.out.println("No one can change anyone name " +
"So First employee name is still :" + aFirstEmp.getName());
}
}
public static void main(String[] args) {
TestProxyPattern testProxyPattern = new TestProxyPattern();
testProxyPattern.runExample();
}}
7. 当我们运行代码，我们将可以输出下面结果：
New name of SunA is >>SunAChanged
SunAChangedYou can't set your grade youself,. You grade is still :1
SunAChangedYou grade is changed by SunB. You grade is now : 5
No one can change anyone name So First employee name is still :SunAChanged
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