一、什么是OGNL
Object Graph Navigation Language对象图导航语言。
是Struts2默认的表达式语言，开源，功能更强大。和EL表达式有点相似
存取对象的属性，调用对象的方法
访问静态方法，静态属性
访问值栈及Stack Context
支持赋值、运算操作、字段类型转化等。
二、简单例子
导入所需要的struts2的包
web.xml增加struts2过滤器
<filter>
<filter-name>struts2</filter-name>
<filter-class>org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>struts2</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
实体类
package com.pb.entity; /*
* 街道实体类
*/
public class Street {
private int streetId; //街道ID
private String streetName; //街道名称 public Street() {
super();
// TODO Auto-generated constructor stub
}
public Street(int streetId, String streetName) {
super();
this.streetId = streetId;
this.streetName = streetName;
}
public int getStreetId() {
return streetId;
}
public String getStreetName() {
return streetName;
}
public void setStreetId(int streetId) {
this.streetId = streetId;
}
public void setStreetName(String streetName) {
this.streetName = streetName;
} }
package com.pb.entity;
/*
* 房子实体类
*/
public class Hourse { private int hourseId; //房屋ID
private String hourseName; //房屋名称
private Street street; //房屋所在街道 public Hourse() {
super();
// TODO Auto-generated constructor stub
}
public Hourse(int hourseId, String hourseName, Street street) {
super();
this.hourseId = hourseId;
this.hourseName = hourseName;
this.street = street;
}
public int getHourseId() {
return hourseId;
}
public String getHourseName() {
return hourseName;
}
public Street getStreet() {
return street;
}
public void setHourseId(int hourseId) {
this.hourseId = hourseId;
}
public void setHourseName(String hourseName) {
this.hourseName = hourseName;
}
public void setStreet(Street street) {
this.street = street;
} }
HourseAction
package com.pb.web.action; import com.opensymphony.xwork2.ActionSupport;
import com.pb.entity.Hourse;
import com.pb.entity.Street; public class HourseAction extends ActionSupport {
private Hourse hourse; @Override
public String execute() throws Exception {
//声明街道对象
Street street =new Street(001,"南新路");
hourse=new Hourse(11,"一房一厅",street);
return SUCCESS;
} public Hourse getHourse() {
return hourse;
} public void setHourse(Hourse hourse) {
this.hourse = hourse;
} }
struts.xml
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE struts PUBLIC
"-//Apache Software Foundation//DTD Struts Configuration 2.3//EN"
"http://struts.apache.org/dtds/struts-2.3.dtd"> <struts> <constant name="struts.enable.DynamicMethodInvocation" value="false" />
<constant name="struts.devMode" value="true" />
<package name="default" namespace="/" extends="struts-default">
<action name="hourse" class="com.pb.web.action.HourseAction">
<result name="success">
/ognl1.jsp
</result>
</action>
</package> </struts>
ognl1.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%@ taglib prefix="s" uri="/struts-tags" %>
<!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>OGNL一</title>
</head>
<body>
房屋的名称：<s:property value="hourse.hourseName"/>
房屋的街道名称:<s:property value="hourse.street.streetName"/>
<s:debug/>
</body>
</html>
在地址栏中输入
http://localhost:8080/OGNLDemo1/hourse.action
发生页面跳转，并取出其中的值
三、访问值栈中的值
四、访问List 、Map、Set
struts.xml
<action name="ognl" class="com.pb.web.action.OgnlAction">
<result name="success">
/ognllist.jsp
</result>
</action>
ognllistAction
package com.pb.web.action; import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set; import com.opensymphony.xwork2.ActionSupport;
import com.pb.entity.Street; public class OgnlAction extends ActionSupport {
/**
*
*/
private static final long serialVersionUID = 1L;
private List<Street> streetList;
private Map<String, Street> streetMap;
private Set <Street> streetSet;
public List<Street> getStreetList() {
return streetList;
}
public void setStreetList(List<Street> streetList) {
this.streetList = streetList;
}
public Map<String, Street> getStreetMap() {
return streetMap;
}
public void setStreetMap(Map<String, Street> streetMap) {
this.streetMap = streetMap;
}
public Set<Street> getStreetSet() {
return streetSet;
}
public void setStreetSet(Set<Street> streetSet) {
this.streetSet = streetSet;
} @Override
public String execute() throws Exception {
streetList=new ArrayList<Street>();
streetList.add(new Street(1, "高新南一路"));
streetList.add(new Street(2, "高新南二路"));
streetList.add(new Street(3, "高新南三路"));
streetMap=new HashMap<String,Street>();
streetMap.put("k1", new Street(4, "高新南四路"));
streetMap.put("k2", new Street(5, "高新南五路"));
streetMap.put("k3", new Street(6, "高新南六路"));
streetSet =new HashSet<Street>();
streetSet.add(new Street(7, "高新南七路"));
streetSet.add(new Street(8, "高新南八路"));
streetSet.add(new Street(9, "高新南九路"));
return SUCCESS;
} }
jsp页页
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%@ taglib prefix="s" uri="/struts-tags" %>
<!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>OGNL一</title>
</head>
<body>
<h1>List</h1>
访问List<s:property value="streetList" /><br/>
访问List中第一个元素:<s:property value="streetList[0].streetName" /><br/>
List中的大小:<s:property value="streetList.size()" /><br/>
List是否为空:<s:property value="streetList.isEmpty()" /><br/>
自定义集合List:<s:property value="{1,2,3,4,5}" /><br/>
自定义集合List访问第一个元素:<s:property value="{1,2,3,4,5}[0]" /><br/>
<hr/>
<h1>Map</h1>
访问Map<s:property value="streetMap" /><br/>
访问Map中第一个元素:<s:property value="streetMap['k1'].streetName" />|<s:property value="streetMap.k1.streetName"/><br/>
访问Map 中所有key:<s:property value="streetMap.keys" /><br/>
访问Map 中所有values:<s:property value="streetMap.values" /><br/>
Map中的大小:<s:property value="streetMap.size()" /><br/>
Map是否为空:<s:property value="streetMap.isEmpty()" /><br/>
自定义集合Map:<s:property value="#{'k1':'v1','k2':'v2','k3':'v3'}" /><br/>
自定义集合Mapt访问第一个元素:<s:property value="#{'k1':'v1','k2':'v2','k3':'v3'}['k1']" />|<s:property value="#{'k1':'v1','k2':'v2','k3':'v3'}.k1" /> <br/>
<hr/>
<h1>Set</h1>
访问Set<s:property value="streetSet" /><br/>
访问Set中第一个元素:<s:property value="streetSet.toArray()[0].streetName" />|<s:property value="streetSet.toArray()[0].streetName"/><br/>
Set中的大小:<s:property value="streetSet.size()" /><br/>
Set是否为空:<s:property value="streetSet.isEmpty()" /><br/>
<hr/>
<s:debug/>
</body>
</html>
在页面中输入：http://localhost:8080/OGNLDemo1/ognl.action访问
五、访问静态方法和投影
5.1、访问静态方法和静态属性
package com.pb.demo;
public class Demo {
public final static String STR="STATIC STR";
public static String staticMethod(){
String info="Demo Static Method";
return info;
}
}
在ognl2.jsp 中可以通过如下代码访问该类的静态属性以及静态方法：
<%@taglib uri="/struts-tags" prefix="s"%>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<h1>OGNL 对象图导航语言</h1>
调用静态方法：<s:property value="@com.pb.demo.Demo@staticMethod()"/> <br>
调用静态常量：<s:property value="@com.pb.demo.Demo@STR"/>
<s:debug/>
</body>
</html>
struts.xml
//开启静态方法
<constant name="struts.ognl.allowStaticMethodAccess" value="true" />
其中<constant>常量你可以去default.properties 文件中查找并复制使用。
5.2、访问投影
选择就是过滤满足选择条件的集合元素。选择操作的语法是：collection.{X YYY},其中X
是一个选择操作符，后面则是选择用的逻辑表达式，而选择操作符有三种：
?选择满足条件的所有元素
^选择满足条件的第一个元素
$选择满足条件的最后一个元素
package com.pb.entity;
/*
* 用户名
*/
public class User {
private Integer age;
private String name;
private String pasword;
public User() {
super();
// TODO Auto-generated constructor stub
}
public User(String name, String pasword, Integer age) {
super();
this.name = name;
this.pasword = pasword;
this.age = age;
}
public Integer getAge() {
return age;
}
public String getName() {
return name;
}
public String getPasword() {
return pasword;
}
public void setAge(Integer age) {
this.age = age;
}
public void setName(String name) {
this.name = name;
}
public void setPasword(String pasword) {
this.pasword = pasword;
} }
package com.pb.web.action; import java.util.ArrayList;
import java.util.List; import com.opensymphony.xwork2.ActionSupport;
import com.pb.entity.User; public class UserAction extends ActionSupport {
private User user;
private List<User> users=new ArrayList<User>();
public User getUser() {
return user;
}
public void setUser(User user) {
this.user = user;
}
public List<User> getUsers() {
return users;
}
public void setUsers(List<User> users) {
this.users = users;
}
@Override
public String execute() throws Exception {
User u1 = new User();
u1.setName("zhangsan");
u1.setPasword("zhangsan");
u1.setAge(10);
this.users.add(u1);
User u2 = new User();
u2.setName("lisi");
u2.setPasword("lisi");
u2.setAge(23);
this.users.add(u2);
User u3 = new User();
u3.setName("wangwu");
u3.setPasword("wangwu");
u3.setAge(22);
this.users.add(u3);
return SUCCESS;
} }
struts.xml
<package name="default" namespace="/" extends="struts-default">
<action name="login" class="com.pb.web.action.UserAction">
<result name="success">
/ognl.jsp
</result>
</action>
</package>
jsp页面
<%@taglib prefix="s" uri="/struts-tags" %>
<!-- 年龄大于18 的所有用户的姓名 -->
集合元素过滤：<s:property value="users.{?#this.age>18}.{name}"/><br/>
<!-- 年龄大于18 的所有用户的第一个用户的姓名 -->
集合元素过滤：<s:property value="users.{^#this.age>18}.{name}"/><br/>
<!-- 年龄大于18 的所有用户的最后一个用户的姓名 -->
集合元素过滤：<s:property value="users.{$#this.age>18}.{name}"/><br/>