Struts2-OGNL表达式

OGNL表达式

OGNL:对象视图导航语言(Object-Graph Navigation Language)，${user.addr.name} 这种写法就叫对象视图导航
OGNL不仅仅可以视图导航，支持比EL表达式更加丰富的功能

1、使用OGNL准备工作

1.1 导包：struts2 的包中已经包含了，所以不需要导入额外的jar包

2.2 代码准备

//准备工作
public void fun1() throws Exception{
	//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();
	//将rootUser作为root部分
	oc.setRoot(rootUser);
	//将context这个Map作为Context部分
	oc.setValues(context);
	//书写OGNL
	Ognl.getValue("", oc, oc.getRoot());
}

2、语法

2.1 基本取值

//基本语法演示
//取出root中的属性值
public void fun2() throws Exception{
	//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());
	System.out.println(name);
	System.out.println(age);
}

//取出context中的属性值
public void fun3() throws Exception{
	//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());
	System.out.println(name);
	System.out.println(name2);
	System.out.println(age);
}

2.2 赋值

//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());
System.out.println(name);
System.out.println(name2);

2.3 调用方法

//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());
		
System.out.println(name);
System.out.println(name2);

2.4 调用静态方法

//Double pi = (Double) Ognl.getValue("@java.lang.Math@PI", oc, oc.getRoot());
Double pi = (Double) Ognl.getValue("@@PI", oc, oc.getRoot());
System.out.println(name);
System.out.println(pi);

2.5 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 name1 = (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(name1);
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());
System.out.println(size2);
System.out.println(name3);
System.out.println(age);