Javaweb Learning JSP Common tags, el expression operators, Jstl tag Library (6)

1 , jsp commonly used tags * As long as supporting JSP files, commonly used tags can be used directly * format: JSP:XXXX * Jsp:forward,complete the forwarding of the JSP page * Page property: Forwarding Address <% request.setcharacterencoding ("UTF-8");%><jsp:forward page= "/index.jsp"> <jsp:param Value= "Zhang San" name= "UserName"/> </jsp:forward> Browse this page will jump to index.jsp page, the browser address is unchanged ${param.username} * Operating principle The JSP engine, which processes the JSP file, parses the specific tag itself and compiles it into Java code Jsp:forward-Application.getrequestdispatcher ("/forward.jsp");* Note: In a JSP page, you can start with a slash * String path= Getabsolutepathrelativetocontext (Relativeurlpath);handle yourself individually, if not/start, automatically add* Jsp:include, dynamic inclusion,merging files when executing the current Servlet * page property: included pages * principle of execution * org.apache.jasper.runtime.JspRuntimeLibrary.inc Lude * Request.getRequestDispatcher.include * Jsp:param,set parameters, use with Jsp:forward or Jsp:include * Name property: Specify the name of the parameter * Value property: Specify the value of the parameter * Jsp:usebean tag: Create class designation Class and adds this class to the scope * Class Property: Specifies the full pathname of the class * ID property: Determines the object's instance object <jsp:usebean ID= "cal" class= "Cn.itcast.domain.Calculator"></jsp:useBean> * jsp:setproperty Tag: Set the property value for the specified JavaBean object * Name property: An existing JavaBean object in the web domain        * Property Properties: Determine the properties of the JavaBean that need to be used * The Value property: determines the specific contents of the setting * param property: Gets the contents of the specified parameter * Note: When the content is null, no value will be assigned <jsp:setproperty Property= "*" Name= "cal" Param= ""/> Get all cal values param to get the value of a parameter, such as Get <input type= "text" name= "Firstnum"/&GT;, you can write <jsp:setproperty property= "*" Name= "cal" param= "Firstnum"/> If the value of Param and property is the same, you can omit the <jsp:setproperty property= "Firstnum" Name= "cal" value= "1"/> The Firstnum property of the Cal object is set to a value of 12 , an operator of the EL expression * performs an operation. * Gets the value of the current object's properties *[]* Write a number and get the value corresponding to the subscript * Write the attribute name, get the corresponding value * escape character: * * invalidate el expression * arithmetic operators, logical operators, relationships operator * Empty three mesh operator
${empty user} returns True or False3. Jstl Tag Library 1, the process of using the Tag Library * Guide Package (myeclipse) * In the current JSP page Header declaration reference * <%@ taglib URI= "Http://java.sun.com/jsp/jstl/core" prefix= "C"%> * taglib directive: Determine the tag library used * URI: Determine the tag library used, specific name * prefix: an alias for the current tag library * Use * <prefix:xxx or < aliases: xxx2, domain object operation * Set: the var attribute to the Web domain setting value: The name of the property: The value of the property property, the scope property: scoping * Page * Request * session * Application <c:set var= "GF" value= "Fengjie" scope= "page"></c:set> <c:set var= "GF" value= "Fengjie" scope= "Request"></c:set> <c:set var= "GF" value= "Fengjie" scope= "Session"></c:set> <c:set var= "GF" value= "Fengjie" scope= "Application"></c:set> \${GF}--${requestscope.gf}<br/> \${GF}--${requestscope.gf}& Lt;br/> \${GF}--${sessionscope.gf}<br/> \${GF}--${APPLICATIONSCOPE.GF}<BR/&G        T * Remove: Delete the value of the web domain with the specified name * var property: OK Name * Note: Delete all scope contents <c:remove var= "GF"/> * out: Content output * Value: Specified content * Note: You can use el Expression * EscapeXML: whether to escape HTML-defined characters * Default value True, Escape * default: Show defaults <c:set var when current output is empty= "GF" value= "<a href= ' # ' >fengjieout</a>" scope= "page"></c:set> <c:out Value= "${gf2}" default= "No Value"></c:out>3, data manipulation * If tag: logical judgment * Test attribute: Logical value True|false * Support El expression <c:set var= "User" value= "xx"></c:set> <c:if Test= "${empty User}"> User object is null <br/> </c:if> * Choose tag: Determines a set of display results that can be selected * When label must be placed * sub-label * When tag: logical judgment * Test attribute: Fill logical value * Otherwis E Tags: handling no processing items, default items <c:choose> <c:when test= "${empty User}"> When:user null </c:when> <c:when test= "${!empty User2}"> When:user NOT NULL </c:when> <C:OTHERWISE&G                        T No processing items </c:otherwise> </c:choose> * foreach tag: Iterate,each piece of information will be displayed in the label Body * Items Property: Determine traversed Object * Support El expression or * Begin property: * End Properties: * Total * var attribute: Determine traversal variable * Step property: Step i+=2 i++--I+=1<c:foreach Items= "${headervalues}" var= "Hvs"> \${hvs}--${hvs.key}: <c:foreach items= "${hvs.value}" var= "H"> ${h} * * * * </c:forEach> <br/> </c:for Each> *url tag: Generates the current response relative to the Web site's completion Path * Value property: The location of the specified page * Note: Content if/start, relative to the current Web project &L T;c:url var= "Demourl" value= "/demo1/calculator.jsp"></c:url>

Javaweb Learning JSP Common tags, el expression operators, Jstl tag Library (6)