String Empty To Null - 将表单字段清空为 null - Spring Editor - StringTrimmerEditor答案

【问题标题】：String Empty To Null - Empty Form Fields to null - Spring Editor - StringTrimmerEditorString Empty To Null - 将表单字段清空为 null - Spring Editor - StringTrimmerEditor
【发布时间】：2014-12-09 06:51:46
【问题描述】：

我已经阅读了几篇文章，并尝试以相同的方式实现，但不知何故我遇到了错误。我想通过XML based configuration实现。

两种方式

基于注释 - 工作正常

@ControllerAdvice
@Controller
public class AppBindingInitializer {

    @InitBinder
    public void initBinder(WebDataBinder binder) {
        binder.registerCustomEditor(String.class, new StringTrimmerEditor(true));
    }

}

基于 XML - 出现错误

<bean id="coreCustomEditors" class="org.springframework.beans.factory.config.CustomEditorConfigurer">
     <property name="customEditors">
        <map>
            <entry key="java.lang.String">
                <bean class="org.springframework.beans.propertyeditors.StringTrimmerEditor">
                    <constructor-arg name="emptyAsNull" value="true" />
                </bean>
            </entry>
        </map>
    </property>
 </bean>

例外

Caused by: org.springframework.beans.TypeMismatchException: Failed to convert property value of type 'java.util.LinkedHashMap' to required type 'java.util.Map' for property 'customEditors'; nested exc
eption is java.lang.IllegalArgumentException: Cannot convert value of type [org.springframework.beans.propertyeditors.StringTrimmerEditor] to required type [java.lang.Class] for property 'customEditor
s[java.lang.String]': PropertyEditor [org.springframework.beans.propertyeditors.ClassEditor] returned inappropriate value of type [org.springframework.beans.propertyeditors.StringTrimmerEditor]
        at org.springframework.beans.BeanWrapperImpl.convertIfNecessary(BeanWrapperImpl.java:479)
        at org.springframework.beans.BeanWrapperImpl.convertForProperty(BeanWrapperImpl.java:511)
        at org.springframework.beans.BeanWrapperImpl.convertForProperty(BeanWrapperImpl.java:505)
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.convertForProperty(AbstractAutowireCapableBeanFactory.java:1502)
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyPropertyValues(AbstractAutowireCapableBeanFactory.java:1461)
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1197)
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:537)
        ... 53 more
Caused by: java.lang.IllegalArgumentException: Cannot convert value of type [org.springframework.beans.propertyeditors.StringTrimmerEditor] to required type [java.lang.Class] for property 'customEdito
rs[java.lang.String]': PropertyEditor [org.springframework.beans.propertyeditors.ClassEditor] returned inappropriate value of type [org.springframework.beans.propertyeditors.StringTrimmerEditor]
        at org.springframework.beans.TypeConverterDelegate.convertIfNecessary(TypeConverterDelegate.java:263)
        at org.springframework.beans.TypeConverterDelegate.convertToTypedMap(TypeConverterDelegate.java:623)
        at org.springframework.beans.TypeConverterDelegate.convertIfNecessary(TypeConverterDelegate.java:208)
        at org.springframework.beans.BeanWrapperImpl.convertIfNecessary(BeanWrapperImpl.java:459)

【问题讨论】：

标签： java spring spring-mvc property-editor

【解决方案1】：

您必须将类名指定为值，而不是 bean（如消息所述），如下所示：

<bean id="coreCustomEditors" class="org.springframework.beans.factory.config.CustomEditorConfigurer">
     <property name="customEditors">
         <map>
             <entry key="java.lang.String" value="your.package.EmptyAsNullStringTrimmerEditor"/>
         </map>
    </property>
</bean>

EmptyAsNullStringTrimmerEditor 是：

package your.package;

public class EmptyAsNullStringTrimmerEditor extends StringTrimmerEditor {
    public YourClass() { super(true); }
}

见CustomEditorConfigurer javadoc

【讨论】：

怎么传<constructor-arg name="emptyAsNull" value="true" />
在第二个选项中，它如何识别哪个编辑器用于哪种类型的数据类型，与第一个选项不同的是，我们提供 `key as java.lanag.String' 和 value 作为其编辑器
对不起，我看错了文档，你必须在这里子类化，看我的编辑
我试过你的方法，做了所有可能的改变，添加依赖等，但似乎是通过 xml 做的，它甚至没有注册我的 bean。但如果我按照我的第一种方法似乎可以正常工作。