Java combat 04javaweb-04jsp, El expression, jstl tag library

First, the JSP part

As long as it is related to the page display is the focus

1. Script for JSP

<%java code%>: Translated into service method interior, local variables, local functions

<%= expression or variable%>: Translated into service method Out.write (expression or variable)

<%!java code%>: The global content, method, global variable that is translated into the servlet

2. How the JSP works

JSP translated into servlet at run time

index.jsp------>work/index_jsp.java----->work/index_jsp.class

3. Comments for JSP

HTML comment:<!--annotation-visible Range: HTML source visible

Java Comment: note written to script///**//***/visible range: translated servlet

JSP Comment: <%--annotation--%> visible Range: JSP source range visible

4. Instructions for JSP

JSP Directive: Page directive taglib Directive include directive

General format for JSP directives: <%@ directive Name attribute = Attribute Value Property = property value%>

(1) Page directive

Configure information for the entire JSP

Property:

Script in language:jsp can embed language code only embedded Java default embedded Java

Import: Importing packages in a JSP

Pageencoding: The code inside of the JSP itself already contains ContentType

ContentType: Translated into Response.setcontenttype ("text/html; CHARSET=GBK ");

Errorpage:jsp the address of the jump after the error

The Iserrorpage:true representative itself is an error-handling page

iselignored:jsp whether the El expression can be resolved by default is False can parse

Session: Whether to create session automatically

The size of the buffer:out buffer can be set to 0KB

(2) Taglib directive

Introducing Tag Libraries

<%@ taglib uri= "" prefix= ""%>

<%@ taglib uri="Http://java.sun.com/jsp/jstl/core" prefix="C" %>

(3) include directive

Contains pages with----static inclusions

<%@ include file="/jsp/j2.jsp" %>

5. The nine implicit objects of JSP (interview written Test frequently asked)

What is an implicit object?

Objects that are used directly in JSP scripts

Request

Response

PageContext

Session

Application

Config

Out

Page

exception

which

Out object: JspWriter

Out.write ()----> page Write content

PageContext object: Context object for the page

1) PageContext is a domain object

Visible Range: Current JSP page

SetAttribute (Name,value)

GetAttribute (name)

RemoveAttribute (name)

SetAttribute (Name,value,scope)

GetAttribute (Name,scope)

RemoveAttribute (Name,scope)

Where scope is the specified domain scope

Pagecontext.setattribute ("name", "Zhangsan", Pagecontext.session_scope);

Findattribute (name);

Bottom-up implementation: Looking for attributes from four domains from small to large in order to find properties after the domain is not looking for

Page domain---->request domain----->session domain----->application domain

${requestscope.name}

${name}-----Bottom Findattribute ()

2) PageContext can get other eight hidden objects

6. JSP tags (JSP actions)

<jsp:include>----interview Frequently asked

Include page----dynamic inclusion

What is the difference between static inclusion and dynamic inclusion?

Static inclusion: The included JSP is first merged with the included JSP at the source level and then translated into a servlet

Dynamic inclusion: Translate two JSPs Separately, and merge the results in the run phase

<jsp:forward>

<jsp:param>

<jsp:useBean>

<jsp:setProperty>

<jsp:getProperty>

Two, El expression

E L (Expression Language) Purpose: To make JSP easier to write

1. El can get data from a domain

${pagescope.name}

${requestscope.name}

${sessionscope.name}

${applicationscope.name}

${name}

2. El can perform operations

${1+1}

${name== ' Zhangsan '? True:false}

${list[2].name== ' Aaa3 '? equals ":" Does Not Equal "}

Keyword empty

${empty objects/variables in the domain}----->true/false

3. El's Built-in Objects 11 (Learn)

Pagescope Requestscope Sessionscope Applicationscope

PageContext

${pagecontext.request.contextpath}

4. El Call function (method)

Steps to use:

1) Introduction of the El Function library
<%@ taglib uri="http://java.sun.com/jsp/jstl/functions" prefix="FN" %>

2) Use the EL function on the JSP page

Syntax: ${FN: function (Parameter)} return value is the result of processing

${fn:touppercase ("Ahdkjalskhd")}

---->ahdkja ....

Three, jstl Tag library

JSTL (JSP standard tag library,jsp tag library), instead of logic code in JSP scripts

1. Jstl the composition of the label

Tag Library function description	The URI of the tag library	Recommended prefixes
Core Tag Library	Http://java.sun.com/jsp/jstl/core	C
XML Tag Library	Http://java.sun.com/jsp/jstl/xml	X
Internationalization / formatting Tag library	Http://java.sun.com/jsp/jstl/fmt	Fmt
Database Tag Library	Http://java.sun.com/jsp/jstl/sql	Sql
EL function	Http://java.sun.com/jsp/jstl/functions	Fn

2. Jstl's core library

Development steps:

1) page introduces Jstl Core library <%@ taglib%>

2) Use the JSTL Core Library tab on the page

JSTL Tags:

<c:forEach>

Two ways to use:

A) Items+var+varstatus

b) Begin+end+var

<c:if>

Test property: Internal is a Boolean judgment

<c:set>

Set data directly to a domain

var: the name of the data in the domain

Value: The value of the data in the field

Scope: which domain

Java combat 04javaweb-04jsp, El expression, jstl tag library