java 如何使用@Named 注释从 Spring 3.0 中的属性注入构造函数参数？
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How to inject constructor parameters from properties in Spring 3.0 with the @Named annotation?
提问by binkley
I'm having trouble putting it all together:
我很难把它们放在一起：
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context.xsd">
<context:property-placeholder location="classpath:some-useful.properties"/>
<context:component-scan base-package="scan.me.scotty"/>
</beans>
Main is this:
主要是这个：
@Named
@Singleton
public class MySpringMain {
@Inject
public MySpringMain(final AReallyCool component) {
component.runForAWhile();
}
public static void main(final String... args) {
new ClassPathXmlApplicationContext(args);
}
}
Component is this:
组件是这样的：
@Named
public class AReallyCool {
@Inject
public AReallyCool(@Named("whoAmI") final String whoAmI) {
// do something here
}
}
And properties is:
和属性是：
whoAmI=Who is anyone, really?
Naturally (for me) Spring dies the death:
自然地（对我来说）春天死了：
Caused by: org.springframework.beans.factory.NoSuchBeanDefinitionException: No matching bean of type [java.lang.String] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {@javax.inject.Named(value=whoAmI)}
Questions:
问题：
- Is this even a reasonable approach?I'm trying to avoid Spring-specific annotations.
- How would you make this work?
- 这甚至是一种合理的方法吗？我试图避免特定于 Spring 的注释。
- 你将如何使这项工作？
回答by Bill
A couple of Spring specific examples may help. As always the documentation at http://static.springsource.org/spring/docs/3.0.x/spring-framework-reference/htmlis quite useful.
一些 Spring 特定示例可能会有所帮助。与往常一样，http://static.springsource.org/spring/docs/3.0.x/spring-framework-reference/html 上的文档非常有用。
To read from a properties file look for the @Value annotation. Example:
要从属性文件中读取，请查找 @Value 注释。例子：
@Component
@Scope("prototype")
@ImportResource("classpath:spring/app-config.xml")
public class RancidService {
private String filepath;
private String filename;
/**
* Default constructor
*
* @param pathname
*/
@Autowired
public RancidService(@Value("#{ nccProperties['rancid.path']}") String filepath) {
this.filepath = filepath;
}
Here is an example of a main function @Autowired in
这是一个主函数@Autowired 的例子
@Component
public class GetCurrentMetric {
/**
* @param args
*/
public static void main(String[] args) {
ApplicationContext context = new ClassPathXmlApplicationContext("classpath:spring/app-config.xml");
GetCurrentMetric p = context.getBean(GetCurrentMetric.class);
p.start(args);
}
@Autowired
private WhipService service;
private void start(String[] args) {
if (args.length != 2) {
System.out.println("Usage: GetCurrentMetric <device> <interface> Example: GetCurrentMetric cr1.lax1 p9/2");
} else {
String device = args[0];
String iface = args[1];
Map<String, String> map = service.getCurrentMetric(device, iface);
if (map.size() == 2) {
System.out.println("Level: " + map.get("level"));
System.out.println("Metric: " + map.get("metric"));
}
}
}
}
EDIT: Missed one important thing, for the properties file example at the top you'll need something in your application context file to tie it together. Example for above:
编辑：错过了一件重要的事情，对于顶部的属性文件示例，您需要在应用程序上下文文件中将其绑定在一起。上面的例子：
<!-- define the properties file to use -->
<util:properties id="nccProperties" location="classpath:spring/ncc.properties" />
