SSH combat OA 04: OGNL expression of Struts2

I haven't had time to update the blog recently. The content of the blog may have to skip the system management module, and I will add it later, but I believe that the blog of the system management module will be added soon. Recently, when I was working on the rights management module, I found that I encountered some unsolvable problems when using el/jstl expressions for echoing and data submission. The problem, so it is to use the OGNL expression of Struts2.

Struts2 supports the following expression languages:

OGNL (Object-Graph Navigation Language), an open source expression language that can easily manipulate object properties;
JSTL (JSP Standard Tag Library), a standard expression language integrated with JSP 2.0;
Groovy, a dynamic language based on the Java platform, has some features of the more popular dynamic languages (such as Python, Ruby and Smarttalk, etc.);
Velocity, strictly speaking is not an expression language, it is a Java-based template matching engine with better performance than JSP.

Jstl is supported in both Struts and Spring Mvc, today's topic is to talk about OGNL.

The simplest case of using OGNL expressions is as follows:

ognl.jsp

<?xml version="1.0" encoding="UTF-8" ?>
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<%@ taglib prefix="s" uri="/struts-tags" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<title>OGNL表达式语言学习</title>
</head>
<body>
    <ol>
        <li>访问值栈中action的普通属性username: <s:property value="username"/>, 
            password: <s:property value="password" />
        </li>
    </ol>

    <s:debug></s:debug>
</body>
</html>

Just like our JSTL, importing OGNL expressions also requires importing our taglib.

OgnlAction.java

public class OgnlAction extends ActionSupport {

    private String username;

    private String password;

    @Override
    public String execute() {

        return SUCCESS;
    }

    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;
    }

}

Enter the following url address in your browser:

http://localhost:8080/struts_ognl/ognl.action?username=shizongger&password=5476499

This url passes username and password to the action in the background. These two values are placed in the value stack and passed to the jsp page. The ognl expression parses these two attributes and displays them on the page.

The struts.xml configuration of the project is as follows:

<?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" />
    <constant name="struts.devMode" value="true" />
    <constant name="struts.ognl.allowStaticMethodAccess" value="true"></constant>
    <include file="/com/shizongger/ognl/ognl.xml"/>

</struts>

Here you need to introduce an xml file, the content of 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.shizongger.ognl.OgnlAction">
            <result>/ognl.jsp</result>
        </action>
</struts>

This is the minimum configuration method of the project. Some comprehensive cases are given below, including accessing the value of the value stack, the access methods of the collection List, Set and Map, etc.

ognl.jsp

    <ol>
        <li>访问值栈中action的普通属性username: <s:property value="username"/>, 
            password: <s:property value="password" />
        </li>
        <li>密码是:<s:password value="password" id="password" name="password" /></li>
        <li>访问对象栈中属性:name:<s:property value="user.name" /> age:<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="user.age"/> | 
            <s:property value="user['age']"/> | 
            <s:property value="user[\"age\"]"/> | 
        </li>
        <li>访问值栈中的普通属性(get set方法):<s:property value="cat.friend.name" /></li>
        <li>字符串<s:property value="username" />，字符串长度(用法一)：<s:property value="username.length()"/></li>
        <li>访问值栈中对象的普通方法：<s:property value="cat.shout('sam')" /> </li>
        <li>访问值栈中action的普通方法：<s:property value="toUpperCase(\"Hello My Name is Shizongger\")" /> </li>
        <li>访问静态方法:转为小写之后的字符串是=[<s:property value="@com.shizongger.ognl.Common@toLowerCase('Hello Csdn')" />],
            长度是:<s:property value="@com.shizongger.ognl.Common@count('Hello Csdn')" /></li>
        <li>访问java.lang包下类的静态方法一:<s:property value="@java.lang.Math@abs('-123')" /></li>
        <li>访问java.lang包下类的静态方法二:<s:property value="@@abs('-123')" /></li>
        <li>访问普通类的构造方法:<s:property value="new com.shizongger.ognl.User.User(22, 'lily')" /></li>
        <hr />

        <li>访问List<s:property value="users" /></li>
        <li>访问List的第一个元素<s:property value="users[0]"/></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List链表中的年龄集合:<s:property value="users.{name}" /></li>
        <li>访问Lis的年龄集合中的第一个: age=<s:property value="users.{age}[0]" />, 
            name=<s:property value="users.{name}[0]"/></li>
        <li>访问Set集合:<s:property value="dogs" /></li>
        <li>访问Set集合的第一个元素<s:property value="dogs[0]" /> </li>
        <li>访问Map的元素:<s:property value="dogMap"/></li>
        <li>访问Map中某个元素:
            <s:property value="dogMap.001"/> | 
            <s:property value="dogMap['001']"/> | 
            <s:property value="dogMap[\"001\"]"/>
        </li>
        <li>访问Map中所有的keys:<s:property value="dogMap.keys" /> </li>
        <li>访问Map中所有的values<s:property value="dogMap.values" /></li>
        <li>得到Map的长度size:<s:property value="dogMap.size()" />|<s:property value="dogMap.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>

OgnlAction.java

import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Set;

import com.opensymphony.xwork2.ActionSupport;

public class OgnlAction extends ActionSupport {

    private String username;

    private String password;

    private User user;

    private Cat cat;

    private List<User> users = new LinkedList<User>();

    private Set<Dog> dogs = new HashSet<Dog>();

    private Map<String, Dog> dogMap = new HashMap<String, Dog>();

    public OgnlAction() {
        dogs.add(new Dog("山姆"));
        dogs.add(new Dog("追风"));

        dogMap.put("001", new Dog("Dog001"));
        dogMap.put("002", new Dog("Dog002"));
        dogMap.put("003", new Dog("Dog003"));
    }

    @Override
    public String execute() {
        users.add(new User(1, "shizongger"));
        users.add(new User(2, "lily"));
        users.add(new User(3, "admin"));
        users.add(new User(4, "root"));
        System.out.println("users list的长度:" + users.size());
        cat = new Cat();
        cat.setFriend(new Dog("山姆"));

        return SUCCESS;
    }

    /**
     * 将传递过来的字符转换为大写
     * @return 返回大写字母
     */
    public String toUpperCase(String str) {
        System.out.println("传递过来的原字符串:" + str);

        return str.toUpperCase();
    }

    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;
    }

    public User getUser() {
        return user;
    }

    public void setUser(User user) {
        this.user = user;
    }

    public Cat getCat() {
        return cat;
    }

    public void setCat(Cat cat) {
        this.cat = cat;
    }

    public List<User> getUsers() {
        return users;
    }

    public void setUsers(List<User> users) {
        this.users = users;
    }

    public Set<Dog> getDogs() {
        return dogs;
    }

    public void setDogs(Set<Dog> dogs) {
        this.dogs = dogs;
    }

    public Map<String, Dog> getDogMap() {
        return dogMap;
    }

    public void setDogMap(Map<String, Dog> dogMap) {
        this.dogMap = dogMap;
    }

}

There are also tools used in Common.java

/**
 * common工具类
 * @author shizongger
 *
 */
public class Common {

    /**
     * 将字符串转换为小写
     * @param str 原字符串
     * @return
     * @throws Exception
     */
    public static String toLowerCase(String str) throws Exception {
        if(str == null || "".equals(str)) {
            return "NULL";
        }

        return str.toLowerCase();
    }

    public static int count(String str) throws Exception {
        if(str == null || "".equals(str)) {
            return 0;
        }

        return str.length();
    }
}

And three javaBeans are used, as follows:

User.java

public class User {
    private int age;

    private String name;

    public User() {
    }

    public User(int age, String name) {
        System.out.println("[age = " + age + ",name = " + name + "]");

        this.age = age;
        this.name = name;
    }

    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }

    @Override
    public String toString() {
        return "User [age=" + age + ", name=" + name + "]";
    }

}

Cat.java

public class Cat {

    private Dog friend;

    public Dog getFriend() {
        return friend;
    }

    public void setFriend(Dog friend) {
        this.friend = friend;
    }

    public String shout(String str) {
        return "miaomiao, my name is " + str;
    }
}

Dog.java

public class Dog {

    private String name;

    public Dog() {

    }

    public Dog(String name) {
        this.name = name;
    }

    public String getName() {
        return name;
    }

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

    @Override
    public String toString() {
        return "dog: " + name;
    }
}

These three javaBeans have rewritten the toString method, in order to facilitate the output of the jsp page. In the jsp page of ongl, in order to view and debug various values at will, you can use the <s:debug> tag to output the value in the value stack.

The browser output is as follows:
write picture description here

Runable case free download csdn_download address

SSH combat OA 04: OGNL expression of Struts2

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