对ognl表达式的简单实现(Ognl.getValue(express,root)),帮助理解ognl表达式的基本原理

package core;

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

/**
 * Created by wyh on 4/11/2017.
 */
public class AccessBean  {
    class foo{
        bar bar;
        public foo(bar bar){this.bar=bar;}
        public AccessBean.bar getBar() {return bar;}}
    class bar{
        String name;
        foobar foobar;
        public bar(){}
        public bar(String name){this.name=name;}
        public bar(foobar foobar){this.foobar=foobar;}
        public String getName() {return name;}
        public foobar getFoobar() {return foobar;}}
    class foobar{
        String name;
        public foobar(String name){this.name=name;}
        public String getName() {return name;}}
    /**
     * 这是获取单个对象即 foo.bar
     * */
    @SuppressWarnings("unchecked")
    public static Object getSingleProperty(Object root, String property) throws NoSuchMethodException, InvocationTargetException, IllegalAccessException {
        Class rootClass=root.getClass();
        //得到getter方法名
        String getterStr="get"+property.substring(0,1).toUpperCase()+property.substring(1);
        //获取getter方法对象
        Method getter=rootClass.getDeclaredMethod(getterStr);
        //实施
        return getter.invoke(root);
    }

    /**
     * 利用循环获取多个对象 foo.bar.foobar
     * 表达式默认是直接从property.property2开始,而不是#root.property.property2这种表达式
     * */
    public static Object getValue(Object root,String ognlExpression) throws NoSuchMethodException, IllegalAccessException, InvocationTargetException {
        //将ognl表达式分解为单个属性
        String[] properties=ognlExpression.split("\\.");
        //循环赋值
        for(String property:properties){
            root=getSingleProperty(root,property);
        }
        return root;
    }
    public static void main(String[] args) throws NoSuchMethodException, IllegalAccessException, InvocationTargetException {
        //创建公有类对象
        AccessBean accessBean=new AccessBean();
        //通过公有类对象创建内部类
        bar bar=accessBean.new bar("i am bar");
        foo foo=accessBean.new foo(bar);
        //获取属性
        System.out.println(getValue(foo,"bar.name"));
        //获取三级属性
        foobar foobar=accessBean.new foobar("i am foobar");
        bar bar2=accessBean.new bar(foobar);
        foo foo2=accessBean.new foo(bar2);

        System.out.println(getValue(foo2,"bar.foobar.name"));
    }
}

package core;

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.HashMap;
import java.util.Map;

/**
 * Created by wyh on 4/11/2017.
 */
public class AccessBean2 {
    class foo{
　　　　 bar bar;
        public foo(bar bar){ this.bar=bar; }
        public AccessBean2.bar getBar() { return bar; }}
    class bar{
        String name;
        foobar foobar;
        public bar(){}
        public bar(String name){this.name=name;}
        public bar(foobar foobar){this.foobar=foobar; }
        public String getName() {return name; }
        public foobar getFoobar() {return foobar;}
    }
    class foobar{
        String name;
        public foobar(String name){this.name=name;}
        public String getName() {return name;}
    }
    /**
     * 这是获取单个对象即 foo.bar
     * */
    @SuppressWarnings("unchecked")
    public static Object getSingleProperty(Object root, String property) throws NoSuchMethodException, InvocationTargetException, IllegalAccessException {
        Class rootClass=root.getClass();
        //得到getter方法名
        String getterStr="get"+property.substring(0,1).toUpperCase()+property.substring(1);
        //获取getter方法对象
        Method getter=rootClass.getDeclaredMethod(getterStr);
        //实施
        return getter.invoke(root);
    }


    public static Object getValueForMap(Map<String,Object> context, String ognlExpression) throws NoSuchMethodException, IllegalAccessException, InvocationTargetException {
        //解析字符串,拿到每个属性
        String[] properties=ognlExpression.split("\\.");
        //获得map中的根key值
        String rootKey=properties[0].substring(1);
        //取出value,作为根节点
        Object root=context.get(rootKey);
        int size=properties.length;
        //因为已经有根节点对象了,从从第二个属性开始循环
        for(int i=1;i<size;i++){
            //这里其实用到了递归,即不断获取这个对象的属性,作为下一个对象(用取出属性来,说明是一个对象),直到循环结束,到达你想要获取的末端属性
            //把一个大实体类,不断解开为被聚合的对象
            root=getSingleProperty(root,properties[i]);
        }
        return root;

    }
    public static void main(String[] args) throws NoSuchMethodException, IllegalAccessException, InvocationTargetException {
        //创建公有类对象
        AccessBean2 accessBean=new AccessBean2();
        //通过公有类对象创建内部类
        bar bar=accessBean.new bar("i am bar");
        foo foo=accessBean.new foo(bar);
        //获取属性
        foobar foobar=accessBean.new foobar("i am foobar");
        bar bar2=accessBean.new bar(foobar);
        foo foo2=accessBean.new foo(bar2);

        Map<String,Object> context=new HashMap<>();
        context.put("foo",foo);
        context.put("foo2",foo2);

        //获取map中"foo"开头的对象的属性
        System.out.println(getValueForMap(context,"#foo.bar.name"));
        //获取map中"foo2"开头的对象的属性
        System.out.println(getValueForMap(context,"#foo2.bar.foobar.name"));
    }
}