springframework内BeanUtils源码使用记录一

package org.springframework.beans;

public abstract class BeanUtils 

    /**
     * Copy the property values of the given source bean into the given target bean.
     * <p>Note: The source and target classes do not have to match or even be derived
     * from each other, as long as the properties match. Any bean properties that the
     * source bean exposes but the target bean does not will silently be ignored.
     * @param source the source bean
     * @param target the target bean
     * @param editable the class (or interface) to restrict property setting to
     * @param ignoreProperties array of property names to ignore
     * @throws BeansException if the copying failed
     * @see BeanWrapper
     */
    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<String> ignoreList = (ignoreProperties != null ? Arrays.asList(ignoreProperties) : null);

        for (PropertyDescriptor targetPd : targetPds) {
            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 value = readMethod.invoke(source);
                            if (!Modifier.isPublic(writeMethod.getDeclaringClass().getModifiers())) {
                                writeMethod.setAccessible(true);
                            }
                            writeMethod.invoke(target, value);
                        }
                        catch (Throwable ex) {
                            throw new FatalBeanException(
                                    "Could not copy property '" + targetPd.getName() + "' from source to target", ex);
                        }
                    }
                }
            }
        }
    }

我们会遇到场景：将某个Bean实例的字段全部或者拷贝到另一个Bean的实例中。

如果是项目没有使用Spring框架，我们只能免为其难，自己写了（当然我们可以把这套代码拷贝过去^_^）[貌似以前没用过Spring时，也不读Spring源码，自己用C#真写过，独读源码很重要！！！]

另外，如果字段比较多（假如几十个），用上述这种反射的方法，比用正则表达式生成的

target.setPropertie1(source.getPropertie1());

target.setPropertie2(source.getPropertie2());

......

效率会降低吗？有时间测试比较一下。

JEECG框架提供了一套上述机制。

另外，通过字节码优化，代替反射机制，则效率更高。与PowerBuilder调用C语言(大学老师这么搞过)，C#调用VC++甚至字节码汇编，基本属于同样的原理。

Python数据计算仍然是调用matlab等库。

https://blog.csdn.net/w05980598/article/details/79134379