如何要求 BeanUtils 忽略空值
使用 Commons beanUtils 我想知道如何要求任何转换器（例如 Dateconverter）忽略 null 值并使用 null 作为默认值。作为一个例子，考虑一个公共类，
public class X {
private Date date1;
private String string1;
//add public getters and setters
}
我的转换器测试为，
public class Apache {
@Test
public void testSimple() throws Exception {
X x1 = new X(), x2 = new X();
x1.setString1("X");
x1.setDate1(null);
org.apache.commons.beanutils.BeanUtils.copyProperties(x2, x1);
//throws ConversionException
System.out.println(x2.getString1());
System.out.println(x2.getDate1());
}
}
上面抛出一个 NPE，因为日期恰好为空。对我来说，这看起来是一个非常原始的场景，应该默认处理（例如，我希望 x2 对于 date1 具有空值）。 doco告诉我，我可以询问 转换器 来执行此操作。有人可以指出我执行此操作的最佳方法吗？
我不想让 Converter 和 isUseDefault() 为 true，因为那样我就必须对所有 Date、Enum 和许多其他转换器执行此操作！
Using Commons beanUtils I would like to know how to ask any converter say the Dateconverter to ignore null values and use null as default. As an example consider a public class,
public class X {
private Date date1;
private String string1;
//add public getters and setters
}
and my convertertest as,
public class Apache {
@Test
public void testSimple() throws Exception {
X x1 = new X(), x2 = new X();
x1.setString1("X");
x1.setDate1(null);
org.apache.commons.beanutils.BeanUtils.copyProperties(x2, x1);
//throws ConversionException
System.out.println(x2.getString1());
System.out.println(x2.getDate1());
}
}
The above throws a NPE since the date happens to be null. This looks a very primitive scenario to me which should be handled by default (as in, I would expect x2 to have null value for date1). The doco tells me that I can ask the converter to do this. Can someone point me as to the best way for doing this ?
I dont want to get hold of the Converter and isUseDefault() to be true because then I have to do it for all Date, Enum and many other converters !
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显然，有一种方法可以告诉 ConvertUtils 不要对空值抛出异常，这是通过调用来实现的
Apparently it looks like, there is a way to tell the ConvertUtils to not throw exceptions on null values which is achieved by calling
最好的解决方案是更新到 BeanUtils 1.9.0，因为这个问题已得到解决，如您在此处看到的 https://issues.apache.org/jira/browse/BEANUTILS-454
The best solution is update to BeanUtils 1.9.0, since this problem is fixed as you can see here https://issues.apache.org/jira/browse/BEANUTILS-454
也许有点晚了，但看起来你可以注册一个 DateConverter
https://issues.apache.org/jira/browse/BEANUTILS-387
Maybe a little late but looks that you can register a DateConverter
https://issues.apache.org/jira/browse/BEANUTILS-387
我最近遇到了这个问题，只是将变量转换为字符串以避免此错误，并在需要时将其转换回日期。这不是最优雅的解决方案，但为了简单起见并避免此类问题，它是一个可行的解决方案。另一个需要注意的是，BeanUtils 会在我的类加载之前触发它的方法，因此我选择了这种方法，而不是使用自定义类加载器来解决问题的更复杂的解决方案。
顺便说一下，在 1.8.0 版本之前，BeanUtils 本身会忽略这些空值。
请参阅此链接：
当字段是具有空值的 java.util.Date 时，没有为“日期”指定值 获取详细解释。
I recently ran into this issue and just converted my variable to a string to avoid this error and converted it back to a date when needed. Not the most elegant solution, but for simplicity and to avoid problems like this, it's a viable solution. The other caveat was that BeanUtils would fire off it's methods before my classes would load, so I opted for this rather than a more complicated solution to the problem using custom classloaders.
By the way, prior to verion 1.8.0, BeanUtils itself would ignore these null values.
See this link:
No value specified for 'Date' when the field is a java.util.Date with a null value for a detailed explanation.
我有点惊讶，像这样在 bean 中设置 null 值这样的简单情况，
会导致崩溃行为，如上所述。
对于它的价值，这是我的解决方法：
I am somewhat amazed that such a simple case as setting a null value in a bean, like this:
causes crashing behavior, as described above.
For what it's worth, here is my workaround: