绑定到 String 属性的 h:inputText 提交空字符串而不是 null
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h:inputText which is bound to String property is submitting empty string instead of null
提问by ThreeFingerMark
I have a JSF 2.0 application on Tomcat with many <h:inputText>fields to input data in my database. Some fields are not required.
我在 Tomcat 上有一个 JSF 2.0 应用程序，其中有许多<h:inputText>字段可以在我的数据库中输入数据。某些字段不是必需的。
<h:inputText value="#{registerBean.user.phoneNumber}" id="phoneNumber">
<f:validateLength maximum="20" />
</h:inputText>
When the user leave this field empty JSF sets empty string ""instead of null.
当用户将此字段留空时，JSF 会设置空字符串""而不是null.
How can I fix this behavior without checking every String with
如何在不检查每个字符串的情况下修复此行为
if (string.equals("")) { string = null; }
回答by BalusC
You can configure JSF 2.x to interpret empty submitted values as null by the following context-paramin web.xml(which has a pretty long name, that'll also be why I couldn't recall it ;) ):
您可以配置JSF 2.x的解释由以下空提交的数据为空context-param的web.xml（其中有一个很长的名字，这也将是为什么我不记得它;））：
<context-param>
<param-name>javax.faces.INTERPRET_EMPTY_STRING_SUBMITTED_VALUES_AS_NULL</param-name>
<param-value>true</param-value>
</context-param>
For reference and for ones who are interested, in JSF 1.2 (and thus not 1.1 or older because it's by design not possible to have a Converterfor java.lang.String) this is workaroundable with the following Converter:
作为参考和感兴趣的人，在 JSF 1.2（因此不是 1.1 或更早版本，因为设计上不可能有Converterfor java.lang.String）这是可以解决的Converter：
public class EmptyToNullStringConverter implements Converter {
public Object getAsObject(FacesContext facesContext, UIComponent component, String submittedValue) {
if (submittedValue == null || submittedValue.isEmpty()) {
if (component instanceof EditableValueHolder) {
((EditableValueHolder) component).setSubmittedValue(null);
}
return null;
}
return submittedValue;
}
public String getAsString(FacesContext facesContext, UIComponent component, Object modelValue) {
return (modelValue == null) ? "" : modelValue.toString();
}
}
...which needs to be registered in faces-config.xmlas follows:
...需要注册faces-config.xml如下：
<converter>
<converter-for-class>java.lang.String</converter-for-class>
<converter-class>com.example.EmptyToNullStringConverter</converter-class>
</converter>
In case you're not on Java 6 yet, replace submittedValue.empty()by submittedValue.length() == 0.
如果您还没有使用 Java 6，请替换submittedValue.empty()为submittedValue.length() == 0.
See also
也可以看看
回答by ThreeFingerMark
i hope this is the right way to say that i can't find a solution for the Problem.
我希望这是正确的说法，我找不到问题的解决方案。
I have add the context-paramto my web.xmlbut it has no result. I use a Tomcat 6.0.24 Server with this two context-param: javax.faces.PROJECT_STAGE =Development javax.faces.VALIDATE_EMPTY_FIELDS = true
我已将其添加context-param到我的web.xml但没有结果。我使用 Tomcat 6.0.24 Server 进行这两个context-param: javax.faces.PROJECT_STAGE =开发javax.faces.VALIDATE_EMPTY_FIELDS = true
