debug小记

Java

copyProperties方法

• Spring的BeanUtils不会copy字段名相同但类型不同的属性

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);
    }
}					

• apache的PropertyUtils::copyProperties若字段名相同但类型不同会抛java.lang.IllegalArgumentException异常
• apache的BeanUtils::copyProperties若字段名相同但类型不同会尝试转换类型后copy, Throws:ConversionException - if conversion cannot be performed successfully

// Convert the specified value to the required type and store it
if (index >= 0) {                    // Destination must be indexed
    value = convertForCopy(value, type.getComponentType());
    try {
        getPropertyUtils().setIndexedProperty(target, propName,
                                         index, value);
    } catch (final NoSuchMethodException e) {
        throw new InvocationTargetException
            (e, "Cannot set " + propName);
    }
}

String::substring(startIndex, endIndex) 方法的endIndex参数若大于字符串长度会直接抛异常, 而并非认为取剩余的所有字符

    public String substring(int beginIndex, int endIndex) {
        if (beginIndex < 0) {
            throw new StringIndexOutOfBoundsException(beginIndex);
        }
        if (endIndex > value.length) {
            throw new StringIndexOutOfBoundsException(endIndex);
        }
        int subLen = endIndex - beginIndex;
        if (subLen < 0) {
            throw new StringIndexOutOfBoundsException(subLen);
        }
        return ((beginIndex == 0) && (endIndex == value.length)) ? this
                : new String(value, beginIndex, subLen);
    }