[ FLib ] JExpect : Python Pexpect 的 Java 版本 (1)

Preface 
Python 的 Pexpect 模組 提供使用者能夠與互動的程式進行溝通: 

Pexpect is a pure Python module for spawning child applications; controlling them; and responding to expected patterns in their output. Pexpect works like Don Libes’ Expect. Pexpect allows your script to spawn a child application and control it as if a human were typing commands.

而這裡的 JExpect 可以想像成Pexpect 模組 的 Java 版本, 並封裝到 Flib.jar 模組. 底下將針對該類別的使用進行介紹. 

Usage Of JExpect 
JExpect 上提供靜態方法 Spawn(String cmd) 讓你可以透過 Spawn 一個新的 Process 來執行給定命令: 

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1. /** 
2. * BD: Spawn a Process by executing given command. 
3. *  
4. * @param cmd: Command to execute in Spawn process. 
5. * @return 
6. * @throws Exception 
7. */  
8. public static ISpawnProcess Spawn(String cmd) throws Exception  

假設我們有一個互動的程式 HelloShell.jar (download), 使用如下: 

$ java -jar HelloShell.jar
This is Hello Shell:
> name
My name is John
> age
My age is 35
> test
Sorry, unknown workd='test'!
> bye
Nice to meet you!
Bye! # 返回 Bash Shell interactive

則你可以使用下面代碼啟動此互動程式, 並使用返回的 ISpawnProcess 介面的實作物件進行與程式互動: 

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1. ISpawnProcess sp = JExpect.Spawn("java -jar HelloShell.jar")  

接著你可以使用ISpawnProcess 介面上的方法將輸入送到 Stdin 中 (模擬從鍵盤輸入): 

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1. /** 
2. * Send input line to System.in. 
3. *  
4. * @param line: Line to be sent to System.in 
5. * @throws Exception 
6. */  
7. public void sendLine(String line) throws Exception;  

或是透過下面 API 對 Stdout/Stderr 進行 Pattern 比對: 

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1. public Future expect_asyn(String pattern) throws Exception;  
2. public boolean expect_async(String pattern, int timeout) throws Exception;  
3. public boolean expect(String pattern, int timeout) throws Exception;  
4. public boolean expect(String pattern) throws Exception;  
5. public boolean expect_exact(String pattern, int timeout) throws Exception;  
6. public boolean expect_exact(String pattern) throws Exception;  

譬如你可以在進入 Interactive 前針對 Hello Shell 在 Stdout 上輸出的 "This is Hello Shell" 中的 "Hello Shell" 字串來判斷目前已經成功進入互動模式, 範例代碼如下: 

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1. ISpawnProcess sp = JExpect.Spawn("java -jar HelloShell.jar")    
2. if(sp.expect_async("Hello Shell", 2000))  
3. {  
4.     printf("\t[Info] Entering Interactive console...\n")  
5. }    
6. else  
7. {  
8.     printf("\t[Error] Fail to open Interactive console!\n")  
9.     sp.close()  // Close Spawn Process  
10. }  

接著你便可以透過 sendLine(String msg) 傳送命令到 Stdin 與程式互動, 並從 lastExpect 取出比對到預期 String pattern 中所有 Stdout 輸出的內容: 

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1. sp.sendLine("name")  
2. printf("\t[Info] Expect Name...\n")  
3. sp.expect("My name is", 2000)  
4. printf("\t${sp.lastExpect[-1]}\n")  

底下為完整的 Groovy 範例代碼與此互動程式進行互動: 

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1. import flib.util.system.ISpawnProcess  
2. import flib.util.system.JExpect  
3.   
4. printf("\t[Info] Enter Interactive App...\n")  
5. ISpawnProcess sp = JExpect.Spawn("java -jar HelloShell.jar")  
6.   
7. printf("\t[Info] Expect Interactive...\n")  
8. sp.expect_async("Hello Shell", 2000)  
9.   
10. sp.sendLine("name")  
11. printf("\t[Info] Expect Name...\n")  
12. sp.expect_async("My name is", 2000)  
13. printf("\t${sp.lastExpect[-1]}\n")  
14.   
15. sp.sendLine("age")  
16. printf("\t[Info] Expect Age...\n")  
17. sp.expect_async("My age is", 2000)  
18. printf("\t${sp.lastExpect[-1]}\n")  
19.   
20. sp.sendLine("test")  
21. printf("\t[Info] Expect Error...\n")  
22. sp.expect_async("unknown", 2000)  
23. printf("\t${sp.lastExpect[-1]}\n")  
24.   
25. sp.sendLine("bye")  
26. printf("\t[Info] Expect Bye...\n")  
27. sp.expect_async("Bye", 2000)  
28. printf("\t${sp.lastExpect[-1]}\n")  
29.   
30.   
31. printf("\t[Info] Done...\n")  
32. sp.close()  
33. printf("\t[Info] Exit main...\n")  

執行結果如下: 

$ groovy -cp "../glibs/*:Flib.jar" HelloShellTest.groovy # JExpect 封裝於 Flib.jar 中
[Info] Change password of user='test'...
[Info] Expect Interactive...
[Info] Expect Name...
> My name is John
[Info] Expect Age...
> My age is 35
[Info] Expect Error...
> Sorry, unknown workd='test'!
[Info] Expect Bye...
Bye!
[Info] Done...
[Info] Exit main...

Supplement 
* Flib - frequent-used-functionality 
* [ Python 文章收集 ] python Pexpect