JavaWeb学习十(JavaBean和EL表达式)

一.JavaBean

1.JavaBean实例

public class Person {

//必须要为成员提供get/set方法(两者只提供一个也是可以的)
//必须要有默认构造器(无参的)
//一般对于具有get/set方法的成员变量称之为属性

//其实就算一个属性没有对应的成员变量,只有get/set方法也是可以的!
//属性的名称就是get/set方法去除get/set后,再把首字母小写了!

private String username;
private int age;
private String address;

public String getId() {
return "asdfghjkl";
    }


public String getName() {
return username;
    }


public void setName(String username) {
this.username = username;
    }


public int getAge() {
return age;
    }


public void setAge(int age) {
this.age = age;
    }


public String getAddress() {
return address;
    }


public void setAddress(String address) {
this.address = address;
    }

}

2.JavaBean的规范:

必须要有一个默认构造器
提供get/set方法,如果只有get方法,那么这个属性是只读属性!
属性:有get/set方法的成员,还可以没有成员,只有get/set方法。属性名称由get/set方法来决定!而不是成员名称!(就像上面成员变量定义成username,但getName,setName,它的属性就是name,而不是username)
方法名称满足一定的规范,那么它就是属性!boolean类型的属性,它的读方法可以是is开头,也可以是get开头

 private boolean bool;




public boolean isBool() {
return bool;
    }

/*public boolean getBool(){
 return bool;
 }*/

public void setBool(boolean bool) {
this.bool = bool;
    }

3.内省

JavaWeb学习十(JavaBean和EL表达式)

内省类 –> Bean信息 –> 属性描述符 –> 属性的get/set对应的Method! –>可以反射
导包

              commons-beanutils.jar
              commons-logging.jar

我们这里提供了jar包的链接如下

内省所需jar包

 @Test
        public void fun1() throws ClassNotFoundException, InstantiationException, IllegalAccessException, InvocationTargetException, NoSuchMethodException {
            String path="cn.st.domain.Person";
            Class class1=Class.forName(path);
            Object bean=class1.newInstance();

            BeanUtils.setProperty(bean,"name","zhangsan");
            BeanUtils.setProperty(bean,"age",12);
            BeanUtils.setProperty(bean,"address","成都东软学院");

            String name=BeanUtils.getProperty(bean,"name");
            int age=Integer.parseInt(BeanUtils.getProperty(bean,"age"));
            String address=BeanUtils.getProperty(bean,"address");

            System.out.println("姓名:"+name+" 年龄:"+age+" 地址:"+address);
        }

控制台打印

姓名:zhangsan 年龄:12 地址:成都东软学院

把一个Map对象封装到一个bean里面去

 @Test
        public void fun2() throws IllegalAccessException, InvocationTargetException {
               Map<String,String> map1=new HashMap<String,String>();
               map1.put("username","zhangsan");
               map1.put("password","123456789");

               User user=new User();

               BeanUtils.populate(user,map1);

               System.out.println(user.getUsername());
               System.out.println(user.getPassword());
        }

User类

public class User {

private String username;
private String password;
public String getUsername() {
return username;
    }
public void setUsername(String username) {
this.username = username;
    }
public String getPassword() {
return password;
    }
public void setPassword(String password) {
this.password = password;
    }


}

我们可以来把map封装进一个javabean对象做成一个方法,如下所示

 public static <T> T toBean(Map map, Class<T> clazz){

try {
//创建javabean
                  T bean=clazz.newInstance();

//封装map到javabean对象中
                  BeanUtils.populate(bean,map);

//返回javabean对象 
return bean;

                 }catch (Exception e) {
throw new RuntimeException();
                }

       }

我们来进行测试一下

public void fun3() {
Map<String,String> map=new HashMap<String,String>();
map.put("username","zhangsan");
map.put("password","123456789");                    
               User user=CommonUtils.toBean(map,User.class);               
               System.out.println(user);

}

控制台打印

User [username=zhangsan, password=123456789]

4.jsp中与javaBean相关的标签

<jsp:useBean>:创建或查询bean
- <jsp:useBean id="user1" class="cn.st.domain.User" scope="session"/> 在session域中查找名为user1的bean,如果不存在,创建之
- <jsp:useBean id="user1" class="cn.st.domain.User" scope="session"/>
<jsp:setProperty>
- <jsp:setProperty property="username" name="user1" value="admin"/> 设置名为user1的这个javabean的username属性值为admin
<jsp:getProperty>
- <jsp:getProperty property="username" name="user1"> 获取名为user1的javabean的名为username属性值

<%@ page language="java" contentType="text/html; charset=UTF-8"
 pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<jsp:useBean id="user1" class="cn.st.domain.User" scope="session"></jsp:useBean>
<jsp:setProperty property="username" name="user1" value="zhangsan"/>
<jsp:setProperty property="password" name="user1" value="123456789"/>
<%
 out.print(session.getAttribute("user1"));

 %>
</body>
</html>

页面运行效果

JavaWeb学习十(JavaBean和EL表达式)

二.EL表达式

1.EL表达式简介

(1).EL是JSP内置的表达式语言

jsp2.0开始不让再使用Java脚本,而是使用el表达式和动态标签来替代java脚本
EL替代的是<%=…%>,也就是说,EL只能做输出! JSTL标签才能设置

(2).EL表达式来读取四大域

${xxx} 全域查找名为xxx的属性,如果不存在,输出空字符串,而不是null,查找范围是从小范围到大范围
${pageScope.xxx},${requestScope.xxx},${sessionScope.xxx},${applicationScope.xxx}指定域获取属性!

<%@ page language="java" contentType="text/html; charset=UTF-8"
 pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<%
 pageContext.setAttribute("xxx","page_xxx");
request.setAttribute("xxx","request_xxx");
 session.setAttribute("xxx","session_xxx");
 application.setAttribute("xxx","application_xxx");

 %>

           ${xxx}<br/>
           ${pageScope.xxx}   <br/>
           ${requestScope.xxx}   <br/>
           ${sessionScope.xxx}   <br/>
           ${applicationScope.xxx}   <br/>
</body>
</html>

页面打印

page_xxx
page_xxx 
request_xxx 
session_xxx 
application_xxx

(3).javaBean导航

public class Employee {
private String name;
private String salary;
private Address address;
            @Override
public String toString() {
return "Employee [name=" + name + ", salary=" + salary + ", address=" + address + "]";
            }
public String getName() {
return name;
            }
public void setName(String name) {
this.name = name;
            }
public String getSalary() {
return salary;
            }
public void setSalary(String salary) {
this.salary = salary;
            }
public Address getAddress() {
return address;
            }
public void setAddress(Address address) {
this.address = address;
            }

public String getHehe() {//普通方法带get并且大写方法名中的第一个字符可以用EL表达式来获取
return "呵呵";
            }
}


public class Address {

private String city;
private String stress;
    @Override
public String toString() {
return "Address [city=" + city + ", stress=" + stress + "]";
    }
public String getCity() {
return city;
    }
public void setCity(String city) {
this.city = city;
    }
public String getStress() {
return stress;
    }
public void setStress(String stress) {
this.stress = stress;
    }


}

<%@page import="cn.st.domain.Address"%>
<%@page import="cn.st.domain.Employee"%>
<%@ page language="java" contentType="text/html; charset=UTF-8"
 pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<%
 Employee employee=new Employee();
 employee.setName("zhangsan");
 employee.setSalary("5000");

 Address address=new Address();
 address.setCity("chengdou");
 address.setStress("京东街道");

 employee.setAddress(address);

request.setAttribute("emp",employee);
 %>

           ${emp.address.city}<br/>
           ${emp.hehe }
</body>
</html>

页面运行效果

chengdou
呵呵

(4).EL表达式运算符

JavaWeb学习十(JavaBean和EL表达式)

(5).EL可以输出的东西都在11个内置对象中!11个内置对象,其中10个是Map,pageContext不是map 它就是PageContext类型,1个顶9个

参数的内置对象
- param:Map<String,String>类型param对象可以用来获取参数,key是参数名,value是参数值,适用于单值的参数
- paramValues:Map<String,String[]>类型,对应参数 key是参数名,value是多个参数值,适用于多值的参数

<%@ page language="java" contentType="text/html; charset=UTF-8"
 pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<%--map.key这是el的语法!
 map['key']也可以操作map
 --%>
              ${param.username}<br/>
              ${paramValues.hobby[0] }<br/>
              ${paramValues.hobby[1] }<br/>
</body>
</html>

访问http://localhost:8080/javaweb8/el/c.jsp?username=123456789&hobby=123&hobby=321
页面打印

123456789
123
321

请求头内置对象
- header:对应请求头Map,key表示头名称,value是单个头值,适用于单值的参数,User-Agent
- headerValues:对应请求头Map,key表示头名称,value是多个头值,适用于多值的参数
- initParam:获取<context-param>内的参数

<%@ page language="java" contentType="text/html; charset=UTF-8"
 pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>


              ${header['User-Agent'] }
</body>
</html>

页面打印效果
JavaWeb学习十(JavaBean和EL表达式)

在web.xml中添加以下信息

 <context-param>
         <param-name>xxx</param-name>
         <param-value>XXX</param-value>
  </context-param>

  <context-param>
         <param-name>yyy</param-name>
         <param-value>YYY</param-value>
  </context-param>

<%@ page language="java" contentType="text/html; charset=UTF-8"
 pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>


              ${initParam.xxx }<br/>
               ${initParam.yyy }
</body>
</html>

页面显示效果
JavaWeb学习十(JavaBean和EL表达式)

Cookie相关内置对象
- cookie:Map<String,Cookie>类型,其中key是cookie的name,value是cookie对象

获取当前JSESSIONID的值

<%@ page language="java" contentType="text/html; charset=UTF-8"
 pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
           ${cookie.JSESSIONID.value }<!--这个cookie对象的值-->
           ${cookie.JSESSIONID.name}<!--这个cookie对象的名字-->
           ${cookie.JSESSIONID}<!--这个cookie对象的toString方法-->
</body>
</html>

页面显示效果

JavaWeb学习十(JavaBean和EL表达式)

pageContext对象
- pageContext:他是PageContext类型

<%@ page language="java" contentType="text/html; charset=UTF-8"
 pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
           ${pageContext.request.scheme }<!-- 协议 --><br/>
            ${pageContext.request.method }<!-- 请求方式 --><br/>
             ${pageContext.request.contextPath }<!-- 当前项目名,前面有斜线 --><br/>
             ${pageContext.session.id }<!-- 获取sessionid -->

</body>
</html>

页面显示效果

JavaWeb学习十(JavaBean和EL表达式)

2.EL函数库(由JSTL提供的)

注意:像Myeclipse就不需要进行导包,eclipse想使用则需要导入一个jstl的jar包

jstl-1.2.jar

导入标签库: <%@ tablib prefix="fn" uri="http://java.sun.com/jsp/jstl/functions"%>
String toUpperCase(String input):把参数转换成大写
String toLowerCase(String input):把参数转换成小写
int indexOf(String input,String substring):从大串输出小串的位置
boolean contains(String input,String substring):查看大串中是否包含小串
boolean containsIgnoreCase(String input,String substring):忽略大小写的是否包含
boolean startsWith(String input,String substring):是否以小串为前缀
boolean endsWith(String input,String substring):是否以小串为后缀
String substring(String input,int beginIndex,int endIndex):截取子串
String substringAfter(String input,String substring):获取大串中小串所在位置后面的字符串
String substringBefore(String input,String substring):获取大串中小串所在位置前面的字符串
String escapeXml(String input):把input中”<” “>” “&” “’” “”” 进行转义
String trim(String input):去除前后空格
String replace(String input,String substringBefore,String sustringAfter):替换
String [] split(String input,String delimiters):分割字符串得到字符串数组
int length(Object obj):可以获取字符串数组各种集合的长度
String join(String array[],String separator):联合字符串数组

<%@page import="java.util.List"%>
<%@page import="java.util.ArrayList"%>
<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%@ taglib prefix="fn" uri="http://java.sun.com/jsp/jstl/functions" %>    
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
           <%
String[] strs={"a","b","c"};
List list = new ArrayList();
           list.add("a");
           pageContext.setAttribute("arr",strs);
           pageContext.setAttribute("list",list);

           %>

${fn:length(arr)}<br/>
${fn:length(list)}<br/>
${fn:toLowerCase("Hello")}<br/>
${fn:toUpperCase("Hello")}<br/>
${fn:contains("abc","a")}<br/>
${fn:containsIgnoreCase("abc","Ab")}<br/>
${fn:contains(arr,"a")}<br/>
${fn:containsIgnoreCase(list,"A")}<br/>
${fn:endsWith("Hello.java",".java")}<br/>
${fn:startsWith("Hello.java","Hell")}<br/>
${fn:indexOf("Hello-World","-")}<br/>
${fn:join(arr,";")}<br/>
${fn:replace("Hello-World","-","+")}<br/>
${fn:join(fn:split("a;b;c",";"),"-")}<br/>
${fn:substring("0123456789",6,9)}<br/>
${fn:substring("0123456789",5,-1)}<br/>
${fn:substringAfter("Hello-World","-")}<br/>
${fn:substringBefore("Hello-World","-")}<br/>
${fn:trim(" a b c ")}<br/>
${fn:escapeXml("<html></html>")}
</body>
</html>

打印效果

3
1
 hello
 HELLO
true
true
true
true
true
true
5
a;b;c
 Hello+World
a-b-c
678
56789
 World
 Hello
a b c
 <html></html>

3.自定义函数库

写一个Java类,类中可以定义0-N个方法,必须是静态的,必须有返回值

public class ELUtils {
public static String fun() {
return "0123456789";
            }
}

           <?xml version="1.0" encoding="UTF-8"?>
<taglib xmlns="http://java.sun.com/xml/ns/j2ee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee
 http://java.sun.com/xml/ns/j2ee/web-jsptaglibrary_2_0.xsd"
version="2.0">


<description>sstt</description>
<tlib-version>1.0</tlib-version><!--版本-->
<short-name>st</short-name><!--短名-->
<uri>http://www.harmel.cn/tag</uri><!--随便写地址-->

<function>
<name>fun</name><!--方法名-->
<function-class>cn.st.common.util.ELUtils</function-class><!--类所在包-->
<function-signature>java.lang.String fun()</function-signature><!--返回类型 以及方法()-->
</function>

</taglib>

在web.xml设置路径

  <jsp-config>
<taglib>
<taglib-uri>http://www.harmel.cn/tag</taglib-uri>
<taglib-location>/WEB-INF/tag/harmel.tld</taglib-location><!--tld所在路径-->
</taglib>
</jsp-config>

在jsp页面中导入标签库

<%@ taglib prefix="st" uri="http://www.harmel.cn/tag" %>//uri写上面web.xml配置的路径

在jsp页面中使用自定义的函数

  ${st:fun() }

页面打印效果

0123456789

END！！！！！！！！！！！！！！！！！

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JavaWeb学习十(JavaBean和EL表达式)

一.JavaBean

1.JavaBean实例

2.JavaBean的规范:

3.内省

4.jsp中与javaBean相关的标签

二.EL表达式

1.EL表达式简介

(1).EL是JSP内置的表达式语言

(2).EL表达式来读取四大域

(3).javaBean导航

(4).EL表达式运算符

(5).EL可以输出的东西都在11个内置对象中!11个内置对象,其中10个是Map,pageContext不是map 它就是PageContext类型,1个顶9个

2.EL函数库(由JSTL提供的)

3.自定义函数库

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