Case

Web Dev

2009-07-29T01:07:00.000-07:00

c15c0 cafe

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What is JSP?

In its basic form, a JSP page is simply an HTML web page that contains additional bits of code that execute application logic to generate dynamic content. This application logic may involve JavaBeans, JDBC objects, Enterprise Java Beans (EJB), and Remote Method Invocation (RMI) objects, all of which can be easily accessed from a JSP page.

Features

Because JSP pages are automatically compiled as needed, web authors can make changes to presentation code without recompiling application logic. This makes JSP a more flexible method of generating dynamic web content than Java servlets, whose functionality JavaServer Pages extend.

Relation JSP - Servlet

Enter JavaServer Pages, which are an extension of the Servlet API. In fact, JSP pages are compiled into servlets before they are used, so they have all of the benefits of servlets, including access to Java APIs. Because JSP pages are generally presentation code with application logic embedded in them, they can be thought of as "inside-out" servlets.

Content

HTML tags are processed by a user's web browser to display the page;

JSP tags are used by the web server to generate dynamic content.

Sample:

<HTML>
<%@ page language="java" imports="java.util.*" %>

<H1>Welcome</H1>

<P>Today is </P>
<jsp:useBean id="clock" class="jspCalendar" />
<UL>
<LI>Day: <%= clock.getDayOfMonth() %>
<LI>Year: <%= clock.getYear() %>
</UL>
<%-- Check for AM or PM --%>
<%! int time = Calendar.getInstance().get(Calendar.AM_PM); %>
<%
if (time == Calendar.AM) {
%>
Good Morning
<%
}
else {
%>
Good Afternoon
<%
}
%>
<%@ include file="copyright.html" %>
</HTML>

Format description

JSP actions (or JSP tags)

perform a variety of functions and extend the capabilities of JSP. JSP actions use XML-like syntax, and are used to (among other things) manage JavaBean components. In the sample page, a jsp:useBean action initializes a JavaBean that is used in subsequent portions of the page:

<jsp:useBean id=="clock" class=="jspCalendar" />

If the sample page had needed to get or set properties of this bean, other JSP actions would have been given, using the following syntax:

<jsp:getProperty name="bean" property="property" />
<jsp:setProperty name="bean" property="property" value="value" />

Directives

instructions that are processed by the JSP engine when the page is compiled to a servlet. Directives are used to set page-level instructions, insert data from external files, and specify custom tag libraries. Directives are defined between <%@ and %>. In the above example, directives define the language of the page (Java), import the Java classes needed by the embedded code, and specify that the contents of an HTML file should be inserted at the bottom of the page:

<%@ page language=="java" imports=="java.util.*" %>
<%@ include file=="copyright.html" %>

Declarations

similar to variable declarations in Java, and define variables for subsequent use in expressions or scriptlets. Declarations are defined between <%! and %>. In the above sample page an int is declared and given a value corresponding to the time of day (AM or PM):

<%! int time = Calendar.getInstance().get(Calendar.AM_PM); %>

Expressions

variables or constants that are inserted into the data returned by the web server, and are defined with the <%= and %>. In the sample page, expressions make calls on a JavaBean component and insert the resulting data into the page:

<%= clock.getDayOfMonth() %>
<%= clock.getYear() %>

Scriptlets

blocks of Java code embedded within a JSP page. Scriptlet code is inserted verbatim into the servlet generated from the page, and is defined between <% and %>. A scriptlet in the above sample determines the time of day and greets the user accordingly:

<%
if (time == Calendar.AM) {
%>
Good Morning
<%
}
else {
%>
Good Afternoon
<%
}
%>

Comments

similar to HTML comments, and are stripped from the page by the JSP engine when it is executed. This means that JSP comments are not returned to the user's browser. Unlike HTML comments, which are given between  tags, JSP comments are given between <%-- and --%>. For example:

<%-- Check for AM or PM --%>

Custom Tag

Tag handler (implements javax.servlet.jsp.Tag) & tag library descriptor.

Sample of using custom tag:

<HTML>
<%@ taglib uri="/tlds/menuDB.tld" prefix="menu" %>

<H1>Today's Menu</H1>

<P>Lunch</P>
<%@ include file="lunch_menu.html" %>

<P>Our Special of the Day</P>
<menu: insertCatchOfDay meal="lunch" >

</HTML>

Applet

Used in HTML, as a tag “applet”. The Applet class should impl the interface java.applet.Applet/javax.swing.JApplet, depends on weather need Swing support.

<html>

<head>

<title>Title</title>

</head>

</body>

</html>

JavaScript

No relation to Java, owned by Netscape but not Sun.

DOCSIS

2009-04-09T10:45:00.000-07:00

JLSNet :: Projects : DOCSIS - 3. Architecture - Protocols: "Error Co"

2009-04-03T07:38:00.001-07:00

status from Ping.fm

2009-04-03T07:37:00.001-07:00

dummy micro-blogs from Ping.fm

recall Maths ...

2009-04-02T22:11:00.000-07:00

e (mathematical constant) - Wikipedia, the free encyclopedia:

The exponential function e^x may be written as a Taylor series

Because this series keeps many important properties for e^x even when x is complex, it is commonly used to extend the definition of e^x to the complex numbers. This, with the Taylor series for sin and cos x, allows one to derive Euler's formula:

which holds for all x. The special case with x = π is known as Euler's identity:

Consequently,

from which it follows that, in the principal branch of the logarithm,

Furthermore, using the laws for exponentiation,

which is de Moivre's formula.

The case,

is commonly referred to as Cis(x).

awk for multiple pattern

2009-04-02T20:36:00.000-07:00

awk /"(CmMacAddr)|(ChSet)|(CmServiceType)"/

windows cheat sheet

2009-02-11T07:49:00.000-08:00

nbstat: tracking IPs: "nbtstat –a "

[socket] shutdown vs close

2008-11-10T07:19:00.000-08:00

for a tcp case,
can used to close read-half, write-half, or both-halves of a connection;
will close the socket, and remove from process resource ...

球迷－孙／9第一次国内转播亮相

2008-10-24T22:13:00.000-07:00

4：30左右的时间，防守可以，但之后一个空位三分偏差较大，突破分球挺没谱。剩下1分钟左右时间，心里那个不舒坦，有点看不下去。感慨一个后卫登录nba的艰辛，能否进入最终名单的担忧，挺复杂。
然后，惊喜来了，右边3分线45度附近得球，面对外线变相运球，左边突破到罚球区右侧顶，面对多人防守，运球后转身晃动后仰跳投，干脆2分。一阵欣喜。
看中国球员就是牵挂，当球迷不容易。

NBA new session...

2008-10-08T09:34:00.000-07:00

Rudy/Oden@Blazer
YAO@Rocket
--
Go go go!

wakeup process from interrupt

2008-10-06T10:32:00.000-07:00

a case of synchronize between process context and interrupt context, this is quite useful for driver code.
e.g. block operation is executed in a user process, which then can be switch out, ISR will be responsible to wake it up, and resume the operation.

in linux, the "WAIT QUEUE" is used to solve such a scenario, for convenience, add an url of this topic here. go back to this topic later.
http://hi.baidu.com/spiderjun/blog/item/d43de7c4bcd3c3ca39db493a.html

while, some other managed object, such as boolean can also be a method, generally,
1. create managed object,
2. wait on it;
3. ISR set the object value to notify the process.
this should be a simple idea especially for the 1-on-1 mode, while queue can deal more complex mode.

[灌水]摄像头之大发现

2008-09-03T09:20:00.000-07:00

身边有个摄像头已经2年多了,今天的发现在于:
1. 镜头有旋钮能调节焦距;
2. 内置了麦克风.

嘿嘿,加班后的惊喜,聊以振奋下,明儿下午打球...

linux mmap: vm_area_struct->vm_ops->nopage

2008-08-28T00:07:00.000-07:00

in case impl mmap with nopage in device driver

sys flow:

page fault when looking at page table
interrupt for the fault
...

--stack1
asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long error_code)
@http://lxr.linux.no/linux-old+v2.4.31/arch/i386/mm/fault.c#L140
{
...
switch (handle_mm_fault(mm, vma, address, write))
...
}

--stack2
int handle_mm_fault(struct mm_struct *mm, struct vm_area_struct * vma,
unsigned long address, int write_access)
@http://lxr.linux.no/linux-old+v2.4.31/mm/memory.c#L1370
{
...
return handle_pte_fault(mm, vma, address, write_access, pte);
...
}

--stack3
static inline int handle_pte_fault(struct mm_struct *mm,
struct vm_area_struct * vma, unsigned long address,
int write_access, pte_t * pte)
@http://lxr.linux.no/linux-old+v2.4.31/mm/memory.c#L1337
{
...
return do_no_page(mm, vma, address, write_access, pte);
...
}

--stack4
static int do_no_page(struct mm_struct * mm, struct vm_area_struct * vma,
unsigned long address, int write_access, pte_t *page_table)
@http://lxr.linux.no/linux-old+v2.4.31/mm/memory.c#L1249
{
..
vma->vm_ops->nopage(vma, address & PAGE_MASK, 0);
..
}

yet another hello world~

2008-02-09T05:55:00.000-08:00

place holder~~