Struts——OGNL表达式与Struts2结合

一、OGNL表达式

OGNL:对象视图导航语言. ${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而且还支持比EL表达式更加丰富的功能.

语法：

public void func() throws OgnlException {
    // 1.准备Root
    User rootUser = new User("jiaxin",23);
    // 2.准备Context
    Map<String,User> context = new HashMap<String,User>();

    context.put("user1",new User("计震宇",22));
    context.put("user2",new User("baoyan",25));
    // 3.实例化OnglContext
    OgnlContext oc = new OgnlContext();
    // 4.设置进OnglContext中
    oc.setRoot(rootUser);
    oc.setValues(context);

    // ***************从root中取值***************
    String name = (String) Ognl.getValue("name", oc, oc.getRoot());
    Integer age = (Integer) Ognl.getValue("age", oc, oc.getRoot());

    System.out.println("name:"+name+"\tage:"+age);

    // ***************从context中取值***************
    String name1 = (String) Ognl.getValue("#user1.name", oc, oc.getRoot());
    Integer age1 = (Integer) Ognl.getValue("#user1.age", oc, oc.getRoot());

    System.out.println("name:"+name1+"\tage:"+age1);

    // ***************赋值****************
    Ognl.getValue("name='计宝宝'", oc, oc.getRoot());
    String name2 = (String) Ognl.getValue("name", oc, oc.getRoot());

    // 先改值再取值
    String name3 = (String) Ognl.getValue("#user1.name='计宝宝',#user1.name", oc, oc.getRoot());

    System.out.println(name2+"\t"+name3);

    // *****************调普通方法****************
    String name4 = (String) Ognl.getValue("setName('计震宇'),getName()", oc, oc.getRoot());

    String name5 = (String) Ognl.getValue("#user2.setName='张军',#user2.getName()", oc, oc.getRoot());

    System.out.println(name4+"\t"+name5);

    // *****************调用静态方法*****************
    Double PI = (Double) Ognl.getValue("@java.lang.Math@PI",oc,oc.getRoot());
    Double PI2 = (Double) Ognl.getValue("@@PI",oc,oc.getRoot());

    System.out.println(PI);

    // ******************创建List，Map对象****************
    Integer len = (Integer) Ognl.getValue("{'ji','zhen','yu','bao'}.size()", oc, oc.getRoot());
    String value = (String) Ognl.getValue("{'ji','zhen','yu','bao'}.get(0)", oc, oc.getRoot());
    String value2 = (String) Ognl.getValue("{'ji','zhen','yu','bao'}[2]", oc, oc.getRoot());

    System.out.println(len+"\t"+value+"\t"+value2);

    // 字典前面要加“#”，注意和取context中的内个“#”没有任何关系
    Integer len2 = (Integer) Ognl.getValue("#{'k1':'v1','k2':'v2'}.size()",oc,oc.getRoot());
    String value3 = (String) Ognl.getValue("#{'k1':'v1','k2':'v2'}['k1']",oc,oc.getRoot());
    String value4 = (String) Ognl.getValue("#{'k1':'v1','k2':'v2'}['k2']",oc,oc.getRoot());

    System.out.println(len2+"\t"+value3+"\t"+value4);
}