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Struts2学习（五）

表达式

1、表达式语言 ( Expression Language )
2、表达式的本质: 就是按照某种规则书写的字符串
3、表达式的处理: 一定有一套程序对表达式中的字符串进行解析和处理，比如 Tomcat
4、常见的表达式

JSP 容器中支持 EL 表达式 ( 因此在 JSP 页面中可以直接使用 )
Spring 中可以使用 Spring Expression Language ( SpEL )
Struts2 中可以使用对象图导航语言Object Graphic Navigation Language（OGNL）

OGNL

1、定义

OGNL 是一种功能强大的表达式语言 ( Expression Language )
OGNL 在非 Web 环境下，需要用到 :javassist-3.20.0-GA.jar，ognl-3.1.12.jar
OGNL 目前是 Apache 基金会下的 commons 项目下的一个小项目: http://commons.apache.org

2、测试案例

OgnlContext两个方法测试案例

package ecut.OGNL.entity;

import java.io.Serializable;

public class Customer implements Serializable {

    private static final long serialVersionUID = 7499870485797565944L;
    
    private String username ;
    private String password ;
    private String confirm ;
    
    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 String getConfirm() {
        return confirm;
    }
    public void setConfirm(String confirm) {
        this.confirm = confirm;
    }

}

package ecut.OGNL;

import java.util.Map;

import ecut.OGNL.entity.Customer;
import ognl.Ognl;
import ognl.OgnlContext;
import ognl.OgnlException;

public class OgnlTest1 {

    public static void main(String[] args) throws OgnlException {
        /*OGNL是通常要结合Struts 2的标志一起使用，如<s:property value="#xx" /> 
        struts页面中不能单独使用，el可以单独使用 ${sessionScope.username} */
        OgnlContext context = new OgnlContext();
        //OgnlContext 实现了Map接口
        System.out.println( context instanceof Map );
        
        // Ognl.setValue( expression , root, value );
        Ognl.setValue( "customer" , context , new Customer() );  // Customer c = new Customer(); context.put( "customer" ,  c ) ;
        
        Ognl.setValue( "customer.username" , context , "张三丰"  ); // c.setUsername( "张三丰" );
        
        // JSP 表达式 : <%= c.getUsername() %>
        // EL 表达式: ${ customer.username }
        // OGNL 表达式 : customer.username(支持OGNL的环境，才可以使用)
        
        Object value = Ognl.getValue( "customer.username" , context ) ; // Ognl.getValue(expression, root)
        System.out.println( value );
        
    }

}

OGNL 在非 Web 环境下需要添加两个jar包，OGNL是通常要结合Struts 2的标志一起使用，如<s:property value="#x" /> struts页面中不能单独使用，el可以单独使用 ${sessionScope.username}。OgnlContext实现了Map接口因此可以使用相应的方法获取属性和设置属性。

单元测试测试案例

package ecut.OGNL;

import org.junit.After;
import org.junit.Before;
import org.junit.Test;

import ecut.OGNL.entity.Customer;
import ognl.Ognl;
import ognl.OgnlContext;
import ognl.OgnlException;

public class OgnlTest2 {

    private OgnlContext root;

    /* @Before 每次test都执行一次，@BeforeClass仅执行一次，方法得是静态的 */
    public @Before void init() throws OgnlException {
        root = new OgnlContext();
        Ognl.setValue("customer", root, new Customer());
        Ognl.setValue("customer.username", root, "张三丰");
    }

    public @Test void testGetValue() throws OgnlException {
        Object value = Ognl.getValue("customer.username", root);
        System.out.println(value);
    }

    public @Test void testSetValue() throws OgnlException {
        Object value = Ognl.getValue("customer.username", root);
        System.out.println(value);
        Ognl.setValue("customer.username", root, "张君宝");
        value = Ognl.getValue("customer.username", root);
        System.out.println(value);
    }

    public @After void destory() {
    }

}

首先要添加Junit 的library，然后新建Junit Test Case ，注解的位置可以在方法前也可以在修饰符后面。

获取对象属性测试案例

package ecut.OGNL.action;

import ecut.OGNL.entity.Customer;

public class CustomerAction {
    
    private Customer customer ;

    public String execute() throws Exception {
        System.out.println( "execute" );
        return "execute" ;
    }
    
    public String login() throws Exception {
        System.out.println( "login" );
        return "login" ;
    }
    
    public String logout() throws Exception {
        System.out.println( "logout" );
        return "logout" ;
    }

    public Customer getCustomer() {
        System.out.println( "CustomerAction # getCustomer()" );
        return customer;
    }

    public void setCustomer(Customer customer) {
        System.out.println( "CustomerAction # setCustomer( Customer )" );
        this.customer = customer;
    }
    
}

package ecut.OGNL;

import org.junit.After;
import org.junit.Before;
import org.junit.Test;

import ecut.OGNL.entity.Customer;
import ecut.OGNL.action.CustomerAction;
import ognl.Ognl;
import ognl.OgnlContext;
import ognl.OgnlException;

public class OgnlTest3 {
    
    private OgnlContext root ;

    public @Before void init() throws OgnlException {
        root = new OgnlContext();
        Ognl.setValue( "customerAction" , root , new CustomerAction() );  
    }

    public @Test void testGetValue() throws OgnlException {
        Object value = Ognl.getValue( "customerAction.customer" , root ) ;
        System.out.println( value );
    }

    public @Test void testSetValue() throws OgnlException {
        Object value = Ognl.getValue( "customerAction.customer" , root ) ;
        System.out.println( value );
        Ognl.setValue( "customerAction.customer" , root , new Customer()  ); 
        Ognl.setValue( "customerAction.customer.username" , root , "张翠山" ); 
        value = Ognl.getValue( "customerAction.customer.username" , root ) ;
        System.out.println( value );
    }

    public @After void destory() {
    }

}

获取方法测试案例

package ecut.OGNL;

import org.junit.After;
import org.junit.Before;
import org.junit.Test;

import ecut.OGNL.action.CustomerAction;
import ognl.Ognl;
import ognl.OgnlContext;
import ognl.OgnlException;

public class OgnlTest4 {
    
    private OgnlContext root ;

    public @Before void init() throws OgnlException {
        root = new OgnlContext();
        Ognl.setValue( "customerAction" , root , new CustomerAction() );  
    }

    public @Test void testGetValue() throws OgnlException {
        Object value = Ognl.getValue( "customerAction.login()" , root ) ;
        System.out.println( value );
    }

    public @Test void testSetValue() throws OgnlException {
    }

    public @After void destory() {
    }

}

转载请于明显处标明出处

https://www.cnblogs.com/AmyZheng/p/9217438.html

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原文地址：https://www.cnblogs.com/AmyZheng/p/9217438.html