JSP技术在1999年由Sun引入，作为对ASP和PHP的回应。Java Server Page在被请求时，会被自动翻译为一个servlet的java文件并编译。当JSP比产生的servlet新时，则会重新翻译生成新的servlet，否则继续重用已有的servlet。载入并初始化servlet实例后，容器会调用jspInit方法。
内嵌java代码
<%@ page import= "java.util.Calendar" %>
<%@ page import= "java.util.Date" %>
<%@ page language= "java" contentType ="text/html; charset=ISO-8859-1"
pageEncoding= "ISO-8859-1" %>
DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "" >
<%! Date now = Calendar.getInstance().getTime(); %>
< html>
< head>
< meta http-equiv ="Content-Type" content= "text/html; charset=ISO-8859-1" >
< title> Embeded Java title>
head>
< body>
<%= now %>
body>
html>
注意：<%! ... %>里的声明代码，在JSP页面没有改动的情况下，只会被执行一次。
使用bean
usebean.jsp
<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
pageEncoding= "ISO-8859-1"%>
DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "" >
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title> Use Bean title>
head>
<body>
<jsp:useBean id= "simpleBean" scope ="application" class= "zp.javaee.SimpleBean"/>
<p> ${simpleBean.currentDate}p >
body>
html>
SimpleBean.java
package zp.javaee;
import java.util.Calendar;
import java.util.Date;
public class SimpleBean {
public Date getCurrentDate() {
return Calendar.getInstance().getTime();
}
}
设置bean的值
SimpleSetValue.jsp
<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
pageEncoding= "ISO-8859-1"%>
<html>
<head >
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title> Yielding and Setting Valuestitle >
head >
<body >
<jsp:useBean id= "simpleBean" scope ="page" class="zp.javaee.SimpleSetValue" />
<jsp:setProperty name= "simpleBean" property ="*"/>
<form method= "post">
Use the input text box below to set the value, and then hit submit.
<br/>< br/>
Set the field value:
<input id= "simpleValue" name ="simpleValue" type= "text" size ="30"/>
<br/>
The value contained within the field is currently:
<jsp:getProperty name= "simpleBean" property ="simpleValue"/>
<input type= "submit">
form>
body >
html>
SimpleSetValue.java
package zp.javaee;
import java.io.Serializable;
public class SimpleSetValue implements Serializable {
/**
*
*/
private static final long serialVersionUID = 4901398509868273864L;
public String getSimpleValue() {
return SimpleValue ;
}
public void setSimpleValue(String simpleValue) {
SimpleValue = simpleValue;
}
private String SimpleValue ;
}
提示：jsp:setProperty里的通配符*使得表单所有的input都会提交给bean。jsp:getProperty等价于EL（Expression Language）表达式${simpleBean.simpleValue}
条件判断
SimpleFunction.jsp
<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
pageEncoding= "ISO-8859-1"%>
DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "" >
<%@ taglib uri="" prefix ="c" %>
<%@ taglib uri="SimpleFunction.tld" prefix= "simple" %>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title> Simple Function title >
head>
<body>
<c:if test= "${simple:simpleFunction(\"\") }">
is empty
c:if>
body>
html>
SimpleFunction.tld
xml version="1.0" encoding="UTF-8"?>
SimpleFunctionClass.java
package zp.javaee;
public class SimpleFunctionClass {
public static boolean simpleFunction(String s) {
return s.isEmpty();
}
}
注意：方法必须是static的，返回boolean。需要使用Java Standard Tag Library (JSTL)，它的"test"属性用于判断条件。
JSPX
JSP的xml版本。
| Tag | Description |
|---|---|
|
|
Defines attributes for a JSP page. |
|
|
Defines an element body. |
|
|
Defines page declarations. |
|
|
Defines page includes and page directives. |
|
|
Executes the body of the JSP tag that is used by the calling JSP page to invoke the tag. |
|
|
Generates an XML element dynamically. |
|
|
Inserts the value of a scripting language expression, converted into a string. |
|
|
Forwards a request to another page. The new page can be HTML, JSP, or servlet. |
|
|
Obtains the value of a bean property and places it in the page. |
|
|
Includes another JSP or web resource in the page. |
|
|
Invokes a specified JSP fragment. |
|
|
Specifies the document type declaration. |
|
|
Executes an applet or bean with the specified plug-in. |
|
|
Defines standard elements and tag library namespaces. |
|
|
Embeds code fragment into a page if necessary. |
|
|
Sets specified value(s) into a bean property. |
|
|
Encloses template data. |
|
|
References and instantiates (if needed) a JavaBean class using a name and providing a scope. |
获得请求参数
< jsp:expression>request.getParameter( "a") jsp:expression>
等价于
${param.a }
自定义tag
SimpleTag.java
xml version= "1.0" encoding ="ISO-8859-1" ?>
<jsp:root xmlns:jsp="" version="2.0">
<jsp:directive.page contentType="text/html; charset=ISO-8859-1"
pageEncoding="ISO-8859-1" session="false"/>
<jsp:output doctype-root-element="html"
doctype-public="-//W3C//DTD XHTML 1.0 Transitional//EN"
doctype-system=""
omit-xml-declaration="true" />
<html xmlns= ""
xmlns:simple="simple" >
<head>
<title> Simple Tag title >
head>
<body>
<simple:simple-tag owner= "zp"/>
body>
html>
jsp:root>
SimpleTag.tld
xml version="1.0" encoding="UTF-8"?>
taglib PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.2//EN" "" >
SimpleTag.jspx
xml version= "1.0" encoding ="ISO-8859-1" ?>
<jsp:root xmlns:jsp="" version="2.0">
<jsp:directive.page contentType="text/html; charset=ISO-8859-1"
pageEncoding="ISO-8859-1" session="false"/>
<jsp:output doctype-root-element="html"
doctype-public="-//W3C//DTD XHTML 1.0 Transitional//EN"
doctype-system=""
omit-xml-declaration="true" />
<html xmlns= ""
xmlns:simple="simple" >
<head>
<title> Insert title heretitle >
head>
<body>
<simple:simple-tag owner= "zp"/>
body>
html>
jsp:root>
提示：tld文件可以放在任何地方，比如WEB-INF/tlds里。
引用别的JSP
xml version= "1.0" encoding ="ISO-8859-1" ?>
<jsp:root xmlns:jsp="" version="2.0">
<jsp:directive.page contentType="text/html; charset=ISO-8859-1"
pageEncoding="ISO-8859-1" session="false"/>
<jsp:output doctype-root-element="html"
doctype-public="-//W3C//DTD XHTML 1.0 Transitional//EN"
doctype-system=""
omit-xml-declaration="true" />
<html xmlns= "" >
<head>
<title> Include JSPtitle >
head>
<body>
<h2> include: h2>
<jsp:include page= "SimpleTag.jspx">
<jsp:param value= "zp" name ="owner"/>
jsp:include>
body>
html>
jsp:root>
错误页面
当一个jsp的脚本运行抛出异常时，可以用
在xxx.jsp里，可以用pageContext.errorData来得到错误信息。比如${pageContext.errorData.statusCode}。
| Expression | Value |
|---|---|
| pageContext.errorData | Provides access to the error information |
| pageContext.exception | Returns the current value of the exception object |
| pageContext.errorData.requestURI | Returns the request URI |
| pageContext.errorData.servletName | Returns the name of the servlet invoked |
| pageContext.errorData.statusCode | Returns the error status code |
| pageContext.errorData.throwable |
Returns the throwable that caused the error |
禁用内嵌java
在web.xml里，配置：
忽略EL
方法1：
\${elBean.myProperty}
方法2：
在web.xml里
方法3：
<%@ page isELIgnored="true" %>