Java中利用動態代理,生成“空”對象的例子

Java中利用動態代理,生成"空"對象的例子:

1. package com.eric.reflect;
3. import java.lang.reflect.InvocationHandler;
4. import java.lang.reflect.Method;
5. import java.lang.reflect.Proxy;
6. import java.util.Arrays;
7. import java.util.Collections;
8. import java.util.List;
10. public class SnowRemovalRobot implements Robot {
11. //generate a NULL robot object
12. static Robot generateNullRobotObj(Robot obj) {
13. return (Robot) Proxy.newProxyInstance(Robot.class.getClassLoader(), new Class[] {Robot.class,Null.class},
14. new NullRobotHandler(obj.getClass()));
15. }
17. public static void main(String[] args) {
18. Robot.Test.test(new SnowRemovalRobot("sample "));
19. System.out.println();
20. Robot.Test.test(generateNullRobotObj(new SnowRemovalRobot("sample ")));
21. }
23. private String name;
25. public SnowRemovalRobot(String name) {
26. this.name = name;
27. }
29. public String name() {
30. return name;
31. }
33. public String model() {
34. return "SnowBot Series 11";
35. }
37. public List<Operation> operations() {
38. return Arrays.asList(new Operation() {
39. public String description() {
40. return name + " can shovel snow";
41. }
43. public void command() {
44. System.out.println(name + " shoveling snow");
45. }
46. }, new Operation() {
47. public String description() {
48. return name + " can chip ice";
49. }
51. public void command() {
52. System.out.println(name + " chipping ice");
53. }
54. }, new Operation() {
55. public String description() {
56. return name + " can clear the roof";
57. }
59. public void command() {
60. System.out.println(name + " clearing roof");
61. }
62. });
63. }
65. }
67. // null object handler, that use dynamic proxy to generate sepcial class null object
68. class NullRobotHandler implements InvocationHandler {
69. private String name;
70. private Robot nullRobot = new NullRobot();
72. public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
73. return method.invoke(nullRobot, args);
74. }
76. public NullRobotHandler(Class<? extends Robot> type) {
77. name = "NULL " + type.getSimpleName() + " obj";
78. }
80. class NullRobot implements Robot, Null {
82. public String name() {
83. return name;
84. }
86. public String model() {
87. return name;
88. }
90. public List<Operation> operations() {
91. return Collections.emptyList();
92. }
94. }
96. }
98. interface Robot {
99. String name();
101. String model();
103. List<Operation> operations();
105. class Test {
106. static void test(Robot robot) {
107. System.out.println("name" + robot.name());
108. System.out.println("model" + robot.model());
109. for (Operation ope : robot.operations()) {
110. System.out.print("description:" + ope.description() + " command:");
111. ope.command();
112. }
113. }
114. }
116. }
118. interface Operation {
119. String description();
121. void command();
122. }
124. /*
125. *
126. * History:
127. *
128. *
129. *
130. * $Log: $
131. */