Dubbo|Dubbo Wrapper 原理与实例 DubboWrapper原理与实例

Dubbo Wrapper 可以认为是一种反射机制。它既可以读写目标实例的字段，也可以调用目标实例的方法。比如

Car是接口；RaceCar是实现类，实现了Car；ferrari和porsche是RaceCar的两个实例
Dubbo为接口Car生成一个Warpper子类，比如Wrapper0；然后创建Wrapper0的实例wrapper0
通过wrapper0#setPropertyValue来修改ferrari的字段，也可以修改porsche的字段
通过wrapper0#invokeMethod来调用ferrari的方法，也可以调用porsche的方法
优点：通过一个Wrapper0实例就可以操作N个目标接口Car的实例

比如我们有一个Car接口，定义了3个方法：

package org.apache.dubbo.common.bytecode; public interface Car { String getBrand(); long getWeight(); void make(String brand, long weight); }

Wrapper#makeWrapper之后生成的Wrapper子类代码如下：

package org.apache.dubbo.common.bytecode; public class Wrapper0 extends Wrapper { // 字段名列表 public static String[] pns; // 字段名与字段类型的映射关系 public static java.util.Map> pts; // 方法名列表 public static String[] mns; // 声明的方法名列表 public static String[] dmns; // 每个public方法的参数类型 public static Class[] mts0; public static Class[] mts1; public static Class[] mts2; public String[] getPropertyNames() { return pns; }public boolean hasProperty(String n) { return pts.containsKey($1); }public Class getPropertyType(String n) { return (Class) pts.get($1); }public String[] getMethodNames() { return mns; }public String[] getDeclaredMethodNames() { return dmns; }public void setPropertyValue(Object o, String n, Object v) { org.apache.dubbo.common.bytecode.Car w; try { w = ((org.apache.dubbo.common.bytecode.Car) $1); } catch (Throwable e) { throw new IllegalArgumentException(e); } throw new org.apache.dubbo.common.bytecode.NoSuchPropertyException("Not found property \"" + $2 + "\" field or setter method in class org.apache.dubbo.common.bytecode.Car."); }public Object getPropertyValue(Object o, String n) { org.apache.dubbo.common.bytecode.Car w; try { w = ((org.apache.dubbo.common.bytecode.Car) $1); } catch (Throwable e) { throw new IllegalArgumentException(e); } if ($2.equals("brand")) { return ($w) w.getBrand(); } if ($2.equals("weight")) { return ($w) w.getWeight(); } throw new org.apache.dubbo.common.bytecode.NoSuchPropertyException("Not found property \"" + $2 + "\" field or setter method in class org.apache.dubbo.common.bytecode.Car."); }public Object invokeMethod(Object o, String n, Class[] p, Object[] v) throws java.lang.reflect.InvocationTargetException { org.apache.dubbo.common.bytecode.Car w; try { w = ((org.apache.dubbo.common.bytecode.Car) $1); } catch (Throwable e) { throw new IllegalArgumentException(e); } try { if ("make".equals($2) && $3.length == 2) { w.make((java.lang.String) $4[0], ((Number) $4[1]).longValue()); return null; } if ("getBrand".equals($2) && $3.length == 0) { return ($w) w.getBrand(); } if ("getWeight".equals($2) && $3.length == 0) { return ($w) w.getWeight(); } } catch (Throwable e) { throw new java.lang.reflect.InvocationTargetException(e); } throw new org.apache.dubbo.common.bytecode.NoSuchMethodException("Not found method \"" + $2 + "\" in class org.apache.dubbo.common.bytecode.Car."); } }

【Dubbo|Dubbo Wrapper 原理与实例】可以认为是重写了JDK的反射机制。