java 如何在 spring 中定义非强制属性？
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how to define not mandatory property in spring?
提问by Julias
I'm using spring 3 with PropertyPlaceholderConfigurator.
我将 spring 3 与 PropertyPlaceholderConfigurator 一起使用。
My properties code looks like as following:
我的属性代码如下所示：
@Configuration
public class MyProps {
@Value("${prop1}")
public String prop1;
...
}
If I do not have a prop1 in my .properties file the spring fails to initialize it's context.
如果我的 .properties 文件中没有 prop1，则 spring 无法初始化它的上下文。
The question is how can I define that this property is not mandatory? some annotation, configuration?
问题是我如何定义这个属性不是强制性的？一些注释，配置？
回答by tibtof
You could use a default value:
您可以使用默认值：
@Value("${prop1:}")
public String prop1;
and spring will inject an empty string if the property isn't defined. The syntax is ${property:defaultValue}.
如果未定义属性，则 spring 将注入一个空字符串。语法是${property:defaultValue}.
回答by adamoldak
I'm not sure if it is possible to make a single property optional but surely you can force the property placeholder to ignore unresolved properties:
我不确定是否可以将单个属性设为可选，但您肯定可以强制属性占位符忽略未解析的属性：
<context:property-placeholder ignore-unresolvable="true" ... />
