Struts2-lesson3

OGNL表达式

Object Graphic Navigation Language

对象，图，导航，语言

OGNL表达式取值范围

OGNL基本语法

// 准备ONGLContext
// 准备Root
User rootUser = new User("tom", 18);
// 准备Context
Map<String, User> context = new HashMap<String, User>();
context.put("user1", new User("jack", 18));
context.put("user2", new User("rose", 22));
OgnlContext oc = new OgnlContext();
oc.setRoot(rootUser);
oc.setValues(context);
// 书写OGNL

// 取出root中user对象的name属性
String name = (String) Ognl.getValue("name", oc, oc.getRoot());
Integer age = (Integer) Ognl.getValue("age", oc, oc.getRoot());

// 取出context中键为user1对象的name属性
String name = (String) Ognl.getValue("#user1.name", oc, oc.getRoot());
String name2 = (String) Ognl.getValue("#user2.name", oc, oc.getRoot());
Integer age = (Integer) Ognl.getValue("#user2.age", oc, oc.getRoot());

// 将root中的user对象的name属性赋值
Ognl.getValue("name='jerry'", oc, oc.getRoot());
String name = (String) Ognl.getValue("name", oc, oc.getRoot());
String name2 = (String) Ognl.getValue("#user1.name='郝强勇',#user1.name",oc, oc.getRoot());

// 调用root中user对象的setName方法
Ognl.getValue("setName('lilei')", oc, oc.getRoot());
String name = (String) Ognl.getValue("getName()", oc, oc.getRoot());
String name2 = (String) Ognl.getValue("#user1.setName('lucy'),#user1.getName()", oc, oc.getRoot());


// 调用静态方法
String name = (String) Ognl.getValue("@cn.itheima.a_ognl.HahaUtils@echo('hello 强勇!')", oc,oc.getRoot());
// Double pi = (Double) Ognl.getValue("@java.lang.Math@PI", oc,
// oc.getRoot());
Double pi = (Double) Ognl.getValue("@@PI", oc, oc.getRoot());

// ognl创建对象-list|map
// 创建list对象
Integer size = (Integer) Ognl.getValue("{'tom','jerry','jack','rose'}.size()", oc, oc.getRoot());
String name = (String) Ognl.getValue("{'tom','jerry','jack','rose'}[0]", oc, oc.getRoot());
String name2 = (String) Ognl.getValue("{'tom','jerry','jack','rose'}.get(1)", oc, oc.getRoot());

/*
 * System.out.println(size); System.out.println(name);
 * System.out.println(name2);
 */
// 创建Map对象
Integer size2 = (Integer) Ognl.getValue("#{'name':'tom','age':18}.size()", oc, oc.getRoot());
String name3 = (String) Ognl.getValue("#{'name':'tom','age':18}['name']", oc, oc.getRoot());
Integer age = (Integer) Ognl.getValue("#{'name':'tom','age':18}.get('age')", oc, oc.getRoot());

OGNL与Struts2的结合

（用List可设计一个栈）

查看值栈中的两部分内容

http://localhost:8080/test_struts2/hello/D3Demo1Action.action

Struts2与ognl结合体现

参数接收中

配置文件中

Struts2标签中

http://localhost:8080/test_struts2/form.jsp

http://localhost:8080/test_struts2/hello/D3Demo3Action.action