Java 如何在Spring中定义一个String数组的bean（使用XML配置）
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How to define a bean of String array in Spring (using XML configuration)
提问by Niranjan
I am trying to define a Spring bean of type String[]and now able to find a way to do so. Sample program is shown below:
我正在尝试定义一个 Spring bean 类型String[]，现在能够找到一种方法来做到这一点。示例程序如下所示：
@Component("sampleClass")
public class SampleClass {
@Value("#{someArrayId}")
private String[] someArray;
public void doWithArray() {
System.out.println(Arrays.toString(someArray));
}
}
Spring XML Configuration
Spring XML 配置
<context:annotation-config />
<context:component-scan base-package="com.demo.spring" />
<util:list id="someArrayId">
<array>
<value>Tiger</value>
<value>Lion</value>
</array>
</util:list>
When I am running the program, I get following exception:
当我运行程序时，出现以下异常：
Exception in thread "main" org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'sampleClass': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: private java.lang.String[] com.demo.spring.SampleClass.someArray; nested exception is org.springframework.beans.ConversionNotSupportedException: Failed to convert value of type 'java.util.ArrayList' to required type 'java.lang.String[]'; nested exception is java.lang.IllegalStateException: Cannot convert value of type [java.lang.Object[]] to required type [java.lang.String]: no matching editors or conversion strategy found
I kind of understand what Spring is complaining, but I don't know how to fix it.
我有点理解 Spring 在抱怨什么，但我不知道如何解决它。
Appreciate if anyone can help.
感谢有人可以提供帮助。
Thanks, NN
谢谢，神经网络
采纳答案by Sotirios Delimanolis
I don't know if this is done for a reason, but this configuration
我不知道这样做是否出于某种原因，但是这种配置
<util:list id="someArrayId">
<array>
<value>Tiger</value>
<value>Lion</value>
</array>
</util:list>
is creating a Listbean that contains one element, a Object[]with two Stringvalues in it.
正在创建一个List包含一个元素的bean，a 中Object[]包含两个String值。
If you actually wanted a Listwith two Stringvalues in it, you should have
如果你真的想要一个List有两个String值的，你应该有
<util:list id="someArrayId">
<value>Tiger</value>
<value>Lion</value>
</util:list>
in which case you could modify your field to be annotated with
在这种情况下，您可以修改要注释的字段
@Value("#{someArrayId.toArray(new java.lang.String[0])}")
Spring's EL resolver will be able to parse it and execute the corresponding method, which will convert the Listto a String[].
Spring的EL解析器将能够分析它并执行相应的方法，这将转换List为String[]。
Alternatively, remove the @Valueannotation and add a @Resourceannotated method
或者，删除@Value注释并添加带@Resource注释的方法
@Resource(name = "someArrayId")
private void init(List<String> bean) {
this.someArray = bean.toArray(new String[0]);
}
I find this cleaner as it's more descriptive.
我觉得这个更简洁，因为它更具描述性。
回答by Evgeniy Dorofeev
try like this
像这样尝试
@Component("sampleClass")
public class SampleClass {
@Value("#{someArrayId.toArray(new String[0])}")
private String[] someArray;
...
<util:list id="someArrayId">
<value>Tiger</value>
<value>Lion</value>
</util:list>
回答by Ahsan Shah
instead of List, just define array. You can also inject it as configuration to make it less ambiguous. Here another point to note is value-typeof array.
而不是List，只需定义数组。您还可以将其作为配置注入，以减少歧义。这里还有一点要注意的是value-type数组。
<bean id="sampleClass" class="somePackage.SampleClass">
<property name="someArray">
<array value-type="java.lang.String">
<value>Tiger</value>
<value>Lion</value>
</array>
</property>
</bean>
