@Autowired bean在另一个bean的构造函数中引用时为null [英] @Autowired bean is null when referenced in the constructor of another bean
问题描述
下面显示的是一段代码,我尝试引用我的ApplicationProperties bean。当我从构造函数引用它时它是null,但是当从另一个方法引用它时它很好。到目前为止,我在其他类中使用这个自动装配的bean没有任何问题。但这是我第一次尝试在另一个类的构造函数中使用它。
Shown below is a snippet of code where I try and reference my ApplicationProperties bean. When I reference it from the constructor it is null, but when referenced from another method it is fine. Up until now I have not had no problem using this autowired bean in other classes. But this is the first time I have tried to use it in the constructor of another class.
在下面的代码片段中,当从构造函数调用时,applicationProperties为null但是在引用时在转换方法中它不是。我缺少什么
In the code snippet below applicationProperties is null when called from the constructor but when referenced in the convert method it is not. What am I missing
@Component
public class DocumentManager implements IDocumentManager {
private Log logger = LogFactory.getLog(this.getClass());
private OfficeManager officeManager = null;
private ConverterService converterService = null;
@Autowired
private IApplicationProperties applicationProperties;
// If I try and use the Autowired applicationProperties bean in the constructor
// it is null ?
public DocumentManager() {
startOOServer();
}
private void startOOServer() {
if (applicationProperties != null) {
if (applicationProperties.getStartOOServer()) {
try {
if (this.officeManager == null) {
this.officeManager = new DefaultOfficeManagerConfiguration()
.buildOfficeManager();
this.officeManager.start();
this.converterService = new ConverterService(this.officeManager);
}
} catch (Throwable e){
logger.error(e);
}
}
}
}
public byte[] convert(byte[] inputData, String sourceExtension, String targetExtension) {
byte[] result = null;
startOOServer();
...
以下是来自ApplicationProperties的s片段......
Below is s snippet from ApplicationProperties ...
@Component
public class ApplicationProperties implements IApplicationProperties {
/* Use the appProperties bean defined in WEB-INF/applicationContext.xml
* which in turn uses resources/server.properties
*/
@Resource(name="appProperties")
private Properties appProperties;
public Boolean getStartOOServer() {
String val = appProperties.getProperty("startOOServer", "false");
if( val == null ) return false;
val = val.trim();
return val.equalsIgnoreCase("true") || val.equalsIgnoreCase("on") || val.equalsIgnoreCase("yes");
}
推荐答案
自动装配(来自沙丘的链接)注释)在构造对象后发生。因此,在构造函数完成之后才会设置它们。
Autowiring (link from Dunes comment) happens after the construction of an object. Therefore they will not be set until after the constructor has completed.
如果需要运行一些初始化代码,您应该能够将构造函数中的代码拉入到方法,并使用 @PostConstruct
。
If you need to run some initialization code, you should be able to pull the code in the constructor into a method, and annotate that method with @PostConstruct
.
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