Spring BeanUtils 的對象復制 copyProperties

Spring提供了一個非常棒的對象復制方法, 其參數的順序和apache commons提供的同名方法是不一樣的, 這個要小心.

源碼

    public static void copyProperties(Object source, Object target) throws BeansException {
        copyProperties(source, target, (Class)null, (String[])null);
    }

    public static void copyProperties(Object source, Object target, Class<?> editable) throws BeansException {
        copyProperties(source, target, editable, (String[])null);
    }

    public static void copyProperties(Object source, Object target, String... ignoreProperties) throws BeansException {
        copyProperties(source, target, (Class)null, ignoreProperties);
    }

    private static void copyProperties(Object source, Object target, Class<?> editable, String... ignoreProperties) throws BeansException {
        Assert.notNull(source, "Source must not be null");
        Assert.notNull(target, "Target must not be null");
        Class actualEditable = target.getClass();
        if(editable != null) {
            if(!editable.isInstance(target)) {
                throw new IllegalArgumentException("Target class [" + target.getClass().getName() + "] not assignable to Editable class [" + editable.getName() + "]");
            }

            actualEditable = editable;
        }

        PropertyDescriptor[] targetPds = getPropertyDescriptors(actualEditable);
        List ignoreList = ignoreProperties != null?Arrays.asList(ignoreProperties):null;
        PropertyDescriptor[] var7 = targetPds;
        int var8 = targetPds.length;

        for(int var9 = 0; var9 < var8; ++var9) {
            PropertyDescriptor targetPd = var7[var9];
            Method writeMethod = targetPd.getWriteMethod();
            if(writeMethod != null && (ignoreList == null || !ignoreList.contains(targetPd.getName()))) {
                PropertyDescriptor sourcePd = getPropertyDescriptor(source.getClass(), targetPd.getName());
                if(sourcePd != null) {
                    Method readMethod = sourcePd.getReadMethod();
                    if(readMethod != null && ClassUtils.isAssignable(writeMethod.getParameterTypes()[0], readMethod.getReturnType())) {
                        try {
                            if(!Modifier.isPublic(readMethod.getDeclaringClass().getModifiers())) {
                                readMethod.setAccessible(true);
                            }

                            Object ex = readMethod.invoke(source, new Object[0]);
                            if(!Modifier.isPublic(writeMethod.getDeclaringClass().getModifiers())) {
                                writeMethod.setAccessible(true);
                            }

                            writeMethod.invoke(target, new Object[]{ex});
                        } catch (Throwable var15) {
                            throw new FatalBeanException("Could not copy property \'" + targetPd.getName() + "\' from source to target", var15);
                        }
                    }
                }
            }
        }

    }

可以看到, 成員變量賦值是基於目標對象的成員列表, 並且會跳過ignore的以及在源對象中不存在的, 所以這個方法是安全的, 不會因為兩個對象之間的結構差異導致錯誤, 但是必須保證同名的兩個成員變量類型相同.