170819-Knowledge points about Jstl

1.JSTL (JSP standard Tag Library)

[1] Jstl Introduction

> Jstl is the standard tag library for JSPs

> Jstl provides us with some common tags for our daily development use (if, if...else, traversal, date formatting)

> tag Library

-Core: Kernel Tag Library

-One of the most commonly used tag libraries, i.e. we are familiar with C tags.

-fn: function Tag Library

-Function Tag Library it needs to be used in conjunction with El expressions, mainly defining some methods of string manipulation.

-FMT: Formatting tag Library

-Mainly used for date, number formatting and internationalization

-20151019 2015/10/19 10/19/2015

-10000 10,000

-SQL: Database Tag Library

-Used primarily to manipulate databases in JSPs, obsolete

-Xml:xml Tag Library

-Used primarily for parsing XML documents in JSP operations, obsolete

> Use of Jstl

Using JSTL requires importing two jar packages Taglibs-standard-impl-1.2.1.jar Taglibs-standard-spec-1.2.1.jar

[2] Core Tag Library

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

-The core tag library generally uses C as the prefix, so we also call the core tag library the C tag. -The C tag is the most commonly used tag library in our Jstl, which encapsulates many of the features commonly used in development.

                                    C:out    function: Enter a content into the page, generally with the EL expression to use!    Example: <c:out value= "" default= "" escapexml= "" ></c:out>    Properties:    value : To output content    default: The default value displayed when the content is empty    escapexml: Whether special characters are automatically escaped, the default is true auto-escaping, and this property is not generally modified     

                                    c:set    function: Set a property in the domain    example: <c:set var= "name" value= "Monkey King" scope= "request" ></c:set>     Properties:    var: Attribute names stored in a domain    value: attribute values stored in a domain    scope: Adding attributes to that field Four optional VALUES (page request session application), default is page   

                                    c: Remove    Action: Remove an attribute from a field    example: <c:remove var= "Name" scope= "Session"/>    properties:     var: The name of the property to remove    scope: The field of the property to remove, four optional VALUES (page request session application)       If this property is not set, the default removal of the specified attribute in four domains.    

                                    c: If    function: Equivalent in Java If statement    example:     <c:if test= "${empty param.name}" >     

                                    C:choose C:when C:otherwise    function: equivalent to If...else    example:     <c:choose>       <c:when test= "${param.score = =" >       

                                    c:foreach    function: You can traverse a collection in a page    example:    <c:foreach items= "${list}" var= "Hero" >      ${hero} <br/>    </c:forEach>         <c:foreach items= "${map}" var= "User" >     ${user.key}---${user.value} <br/>  & Nbsp; </c:foreach>    Properties:    items: The collection to traverse    var: The name of the object reference in the collection            Note: When you traverse a map, you return a set of key-value pairs of structures     We can get through the object. Key gets the key through the object. Value gets        function: Can be used to traverse a set of numbers    example:    <c: ForEach begin= "1" end= "var=" "Index" step= "1" >     <a href=#>${index}</a>   &nBsp; </c:foreach>    Properties:    begin: Starting position, note begin cannot be less than 0    end : End position    var: reference name    step: Step, size per increment    

                                    c:url    Function: Can create a complete absolute path    example:    <c:url value= "/index.jsp" >     <c: param name= "name" value= "Monkey King" ></c:param>     <c:param name= "age" value= "all" >< /c:param>    </c:url>    Properties:    value: The address to be set, note that the address should start with/or not add the project name        You can add the C:param tag to the URL tag to automatically request parameters for the address stitching.      c:redirect    Role: Redirection of Requests    Example:    <c:redirect url= "/ index.jsp ">     <c:param name=" name "value=" Tang priest "></c:param>     </c:redirect>    Properties:    url:      Redirect to Destination address, note that the address does not add the project name by itself.          can add C:param tags to the redirect tag, and can automatically request parameters for the address stitching.        Note: The redirect tag automatically sets the project name for us and does not need to be set manually!         

Three ways to set an absolute path:

1.<c:set var= "CTX" value= "${pagecontext.request.contextpath}" ></c:set> in this way, you can use ${CTX} to replace the project name in the page

2. Use <c:url value= "/index.jsp" ></c:url> use URL tag, it will automatically add the project name to the absolute path

3.<base href= "Http://${pagecontext.request.servername}:${pagecontext.request.serverport}${ PageContext.request.contextPath}/"/> Use the base tag to make all relative paths in the page, plus the project name

[3] Function Tag Library

Role: the function tag library needs to be used in conjunction with the El expression, the method inside it is the operation of some strings into the function tag library: <%@ taglib prefix= "FN" uri= "http://java.sun.com/jsp/jstl/functions "%>

                              Example:           ${fn:contains ("Hello", "He")} <br/> Determine if the previous string contains the last string           ${fn:containsignorecase ("Hello", "He")} <br/> Determines whether the previous string contains the latter string, is case-insensitive           ${fn:endswith ("Hello", "Alo")}<br/> Determine whether the previous string ends after a string           <!--automatically escapes special characters--    ${fn:escapexml ("

170819-Knowledge points about Jstl