OGNL的应用

OGNL介绍：

一：OGNL的全称是Object Graph Navigation Language(对象图导航语言)，

它是一种强大的表达式语言

二：OgnlContext(ongl上下文)

OgnlContext=根对象(1)+非根对象(N)

根对象有且只有一个，非根对象可以有无数个

OnglExpression类：用于OGNL表达计算的一个工具类

（1）getValue：获取值

（2）setValue：取值

package com.lsy.test;

import ognl.Ognl;
import ognl.OgnlContext;
import ognl.OgnlException;

/**
 * 用于OGNL表达计算的一个工具类
 * 
 */
public class OnglExpression {
	private OnglExpression() {
	}

	/**
	 * 根据OGNL表达式进行取值操作
	 * 
	 * @param expression
	 *            ognl表达式
	 * @param ctx
	 *            ognl上下文
	 * @param rootObject
	 *            ognl根对象
	 * @return
	 */
	public static Object getValue(String expression, OgnlContext ctx,
			Object rootObject) {
		try {
			return Ognl.getValue(expression, ctx, rootObject);
		} catch (OgnlException e) {
			throw new RuntimeException(e);
		}
	}

	/**
	 * 根据OGNL表达式进行赋值操作
	 * 
	 * @param expression
	 *            ognl表达式
	 * @param ctx
	 *            ognl上下文
	 * @param rootObject
	 *            ognl根对象
	 * @param value
	 *            值对象
	 */
	public static void setValue(String expression, OgnlContext ctx,
			Object rootObject, Object value) {
		try {
			Ognl.setValue(expression, ctx, rootObject, value);
		} catch (OgnlException e) {
			throw new RuntimeException(e);
		}
	}
}

举例演示

package com.lsy.test;

import ognl.OgnlContext;
import ognl.OgnlException;

public class Demo1 {

	/**
	 * @param args
	 * @throws OgnlException
	 */
	public static void main(String[] args)  {
		Employee e = new Employee();
		e.setName("小李");

		Manager m = new Manager();
		m.setName("张经理");

		// 创建OGNL下文,而OGNL上下文实际上就是一个Map对象
		OgnlContext ctx = new OgnlContext();

		// 将员工和经理放到OGNL上下文当中去
		ctx.put("employee", e);
		ctx.put("manager", m);
		ctx.setRoot(e);// 设置OGNL上下文的根对象

		/** ********************** 取值操作 *************************** */
		// 表达式name将执行e.getName()，因为e对象是根对象(请注意根对象和非根对象表达式的区别)
		String employeeName = (String) OnglExpression.getValue("name", ctx, e);
		System.out.println(employeeName);

		// 表达式#manager.name将执行m.getName()，注意：如果访问的不是根对象那么必须在前面加上一个名称空间，例如：#manager.name
		String managerName = (String) OnglExpression.getValue("#manager.name",
				ctx, e);
		System.out.println(managerName);

		// 当然根对象也可以使用#employee.name表达式进行访问
		employeeName = (String) OnglExpression.getValue("#employee.name", ctx,
				e);
		System.out.println(employeeName);

		/** ********************** 赋值操作 *************************** */
		OnglExpression.setValue("name", ctx, e, "小明");
		employeeName = (String) OnglExpression.getValue("name", ctx, e);
		System.out.println(employeeName);

		OnglExpression.setValue("#manager.name", ctx, e, "孙经理");
		managerName = (String) OnglExpression.getValue("#manager.name", ctx, e);
		System.out.println(managerName);

		OnglExpression.setValue("#employee.name", ctx, e, "小芳");
		employeeName = (String) OnglExpression.getValue("name", ctx, e);
		System.out.println(employeeName);
	}

}

里面有两个实体类

Employee

package com.lsy.test;

public class Employee {
	private String name;

	private Address address;

	private Integer salary;

	public Employee() {
		super();
	}

	public Employee(String name, Integer salary) {
		super();
		this.name = name;
		this.salary = salary;
	}

	public Integer getSalary() {
		return salary;
	}

	public void setSalary(Integer salary) {
		this.salary = salary;
	}

	public String getName() {
		return name;
	}

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

	public Address getAddress() {
		return address;
	}

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

	@Override
	public String toString() {
		return "Employee [name=" + name + ", address=" + address + ", salary=" + salary + "]";
	}

}

Manger

package com.lsy.test;

public class Manager {
	private String name;

	public Manager() {
		super();
	}

	public String getName() {
		return name;
	}

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

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

}

结果展示

值栈的使用

Demo7类

package com.lsy.test;

import com.opensymphony.xwork2.ActionContext;
import com.opensymphony.xwork2.ActionSupport;
import com.opensymphony.xwork2.util.ValueStack;

public class Demo7 extends ActionSupport{
	/**
	 * 
	 * 值栈的使用
	 * 
	 */
	public String ognl1 () {
		// 栈：表示一个先进后出的数据结构
		//获取实栈
		ValueStack vs = ActionContext.getContext().getValueStack();
		// push方法把项压入栈顶
		vs.push(new Employee("zs", 22));
		vs.push(new Employee("ls", 22));
		vs.push(new Employee("ww", 22));

		// pop方法移除栈顶对象并作为此函数的值返回该对象
		Employee e = (Employee) vs.pop();
		System.out.println(e.getName());
		e = (Employee) vs.pop();
		System.out.println(e.getName());
		e = (Employee) vs.pop();
		System.out.println(e.getName());
		return "bookEdit";
	}

	/**
	 * 此例用于模拟struts2的值栈计算过程
	 * 
	 * @param args
	 */
	public String ognl2 () {
		ValueStack vs = ActionContext.getContext().getValueStack();
		vs.push(new Employee("张雇员", 2000));// 1
		vs.push(new Student("小明同学", "s001"));// 0
		System.out.println(vs.findValue("name"));
		System.out.println(vs.findValue("salary"));

		ActionContext ac = ActionContext.getContext();
		return "bookEdit";
	}
}

struts-sy.xml中配置