ognl 表达式常用表达式语言

从一个客户端的请求开始:

先经过Web.xml 到达struts.xml:


<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE struts PUBLIC
    "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"
    "http://struts.apache.org/dtds/struts-2.0.dtd">
    <struts>
        <constant name="struts.enable.DynamicMethodInvocation"
            value="false" />
                  自动编译
                 <constant name="struts.devMode" value="true" />
                访问静态属性和方法要设置的
        <constant name="struts.ognl.allowStaticMethodAccess"
            value="true">
        </constant>
                模块包含,包含ognl.xml
        <include file="/com/bjsxt/struts2/ognl/ognl.xml" />
    </struts>


被包含的ognl.xml:


<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE struts PUBLIC
        "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"
        "http://struts.apache.org/dtds/struts-2.0.dtd">
<struts>
    <package name="ognl" extends="struts-default">
        <action name="ognl" class="com.bjsxt.struts2.ognl.OgnlAction">
            <result>/ognl.jsp</result>
        </action>
        <action name="test" class="com.bjsxt.struts2.ognl.TestAction">
            <result type="chain">ognl</result>
        </action>
    </package>
</struts>



OgnlAction 类:


package com.bjsxt.struts2.ognl;
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;
public class OgnlAction extends ActionSupport {
    private Cat cat;
    private Map<String, Dog> dogMap = new HashMap<String, Dog>();
    private Set<Dog> dogs = new HashSet<Dog>();
    private String password;
    private User user;
    private String username;
    private List<User> users = new ArrayList<User>();
    public OgnlAction() {
        users.add(new User(1));
        users.add(new User(2));
        users.add(new User(3));
        dogs.add(new Dog("dog1"));
        dogs.add(new Dog("dog2"));
        dogs.add(new Dog("dog3"));
                                                                                                                                             
        dogMap.put("dog100", new Dog("dog100"));
        dogMap.put("dog101", new Dog("dog101"));
        dogMap.put("dog102", new Dog("dog102"));
                                                                                                                                             
    }
    public String execute() {
        return SUCCESS;
    }
    public Cat getCat() {
        return cat;
    }
                                                                                                                                         
    public Map<String, Dog> getDogMap() {
        return dogMap;
    }
    public Set<Dog> getDogs() {
        return dogs;
    }
                                                                                                                                         
    public String getPassword() {
        return password;
    }
                                                                                                                                         
    public User getUser() {
        return user;
    }
    public String getUsername() {
        return username;
    }
    public List<User> getUsers() {
        return users;
    }
    public String m() {
        return "hello";
    }
    public void setCat(Cat cat) {
        this.cat = cat;
    }
                                                                                                                                         
    public void setDogMap(Map<String, Dog> dogMap) {
        this.dogMap = dogMap;
    }
    public void setDogs(Set<Dog> dogs) {
        this.dogs = dogs;
    }
    public void setPassword(String password) {
        this.password = password;
    }
    public void setUser(User user) {
        this.user = user;
    }
    public void setUsername(String username) {
        this.username = username;
    }
    public void setUsers(List<User> users) {
        this.users = users;
    }
}

Cat类:

package com.bjsxt.struts2.ognl;
public class Cat {
                                                                                                        
    private Dog friend;
                                                                                                        
    public Dog getFriend() {
        return friend;
    }
    public void setFriend(Dog friend) {
        this.friend = friend;
    }
    public String miaomiao() {
        return "miaomiao";
    }
}

Dog类:

package com.bjsxt.struts2.ognl;
public class Dog {
                                                                                       
    private String name ;
                                                                                       
    public Dog() {
                                                                                           
    }
    public Dog(String name) {
        super();
        this.name = name;
    }
                                                                                       
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    @Override
    public String toString() {
        return "dog: " + name;
    }
}

S类:

package com.bjsxt.struts2.ognl;
public class S {
    public static String STR = "STATIC STRING";
                                                                           
    public static String s() {
        return "static method";
    }
}

User类:

package com.bjsxt.struts2.ognl;
public class User {
    private int age = 8;
                                                                       
    public User() {
                                                                           
    }
                                                                       
    public User(int age) {
        super();
        this.age = age;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
                                                                       
    @Override
    public String toString() {
        return "user" + age;
    }
}

最重要的ognl.jsp(包含访问值栈中各种元素的方法):

<body>
    <ol>
        <li>访问值栈中的action的普通属性: username = <s:property value="username"/> </li>
        <li>访问值栈中对象的普通属性(get set方法):<s:property value="user.age"/> | <s:property value="user['age']"/> | <s:property value="user[\"age\"]"/> | wrong: <%--<s:property value="user[age]"/>--%></li>
        <li>访问值栈中对象的普通属性(get set方法): <s:property value="cat.friend.name"/></li>
        <li>访问值栈中对象的普通方法:<s:property value="password.length()"/></li>
        <li>访问值栈中对象的普通方法:<s:property value="cat.miaomiao()" /></li>
        <li>访问值栈中action的普通方法:<s:property value="m()" /></li>
        <hr />
        <li>访问静态方法:<s:property value="@com.bjsxt.struts2.ognl.S@s()"/></li>
        <li>访问静态属性:<s:property value="@com.bjsxt.struts2.ognl.S@STR"/></li>
        <li>访问Math类的静态方法:<s:property value="@@max(2,3)" /></li>
        <hr />
        <li>访问普通类的构造方法:<s:property value="new com.bjsxt.struts2.ognl.User(8)"/></li>
        <hr />
        <li>访问List:<s:property value="users"/></li>
        <li>访问List中某个元素:<s:property value="users[1]"/></li>
        <li>访问List中元素某个属性的集合:<s:property value="users.{age}"/></li>
        <li>访问List中元素某个属性的集合中的特定值:<s:property value="users.{age}[0]"/> | <s:property value="users[0].age"/></li>
        <li>访问Set:<s:property value="dogs"/></li>
        <li>访问Set中某个元素:<s:property value="dogs[1]"/></li>
        <li>访问Map:<s:property value="dogMap"/></li>
        <li>访问Map中某个元素:<s:property value="dogMap.dog101"/> | <s:property value="dogMap['dog101']"/> | <s:property value="dogMap[\"dog101\"]"/></li>
        <li>访问Map中所有的key:<s:property value="dogMap.keys"/></li>
        <li>访问Map中所有的value:<s:property value="dogMap.values"/></li>
        <li>访问容器的大小:<s:property value="dogMap.size()"/> | <s:property value="users.size"/> </li>
        <hr />
        <li>投影(过滤):<s:property value="users.{?#this.age==1}[0]"/></li>
        <li>投影:<s:property value="users.{^#this.age>1}.{age}"/></li>
        <li>投影:<s:property value="users.{$#this.age>1}.{age}"/></li>
        <li>投影:<s:property value="users.{$#this.age>1}.{age} == null"/></li>
        <hr />
        <li>[]:<s:property value="[0].username"/></li>
           
    </ol>
       
    <s:debug></s:debug>
struts2提供了一个非常好的调试方法.就是在页面上添加一个debug标签..它会自动帮我们将一些信息显示在页面上;这个值栈又分为两种.Value Stack Contents 和 Stack Context .
(1).Value Stack Contents 里面的信息我们可以用 <s:property value="sss"> 这样来直接访问.
(2) Stack Context  里面的信息我们可以 <s:property value="#sss">这样来访问
</body>


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