blocks|key|2006350|text|Spring在独立应用程序中工作。您正在使用错误的方式创建spring+bean。正确的方法如下：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2006351|@Component
public+class+Main+{

++++public+static+void+main(String[]+args)+{
++++++++ApplicationContext+context+=+
++++++++++++new+ClassPathXmlApplicationContext("META-INF/config.xml");

++++++++Main+p+=+context.getBean(Main.class);
++++++++p.start(args);
++++}

++++@Autowired
++++private+MyBean+myBean;
++++private+void+start(String[]+args)+{
++++++++System.out.println("my+beans+method:+"+%2B+myBean.getStr());
++++}
}

@Service+
public+class+MyBean+{
++++public+String+getStr()+{
++++++++return+"string";
++++}
}|code-block|syntax|javascript|2006352|在第一种情况下(问题中的情况)，您将自己创建对象，而不是从Spring上下文中获取它。因此，Spring没有机会对依赖项进行Autowire+(这会导致NullPointerException)。|offset|length|style|CODE|2006353|在第二种情况下(此答案中的情况)，您从Spring上下文中获取bean，因此它是Spring托管的，而Spring负责autowiring。|2006354|entityMap^0|0|0|1Q|8|24|K|0|1N|A|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|S|8|@$I|T|J|U|K|L]|$I|V|J|W|K|L]]|9|@]|A|$]]|$1|M|3|N|5|6|7|X|8|@$I|Y|J|Z|K|L]]|9|@]|A|$]]|$1|O|3|-4|5|6|7|10|8|@]|9|@]|A|$]]]|P|$]]

Spring works in standalone application. You are using the wrong way to create a spring bean. The correct way to do it like this:

<pre><code>@Component
public class Main {

 public static void main(String[] args) {
 ApplicationContext context = 
 new ClassPathXmlApplicationContext("META-INF/config.xml");

 Main p = context.getBean(Main.class);
 p.start(args);
 }

 @Autowired
 private MyBean myBean;
 private void start(String[] args) {
 System.out.println("my beans method: " + myBean.getStr());
 }
}

@Service 
public class MyBean {
 public String getStr() {
 return "string";
 }
}
</code></pre>

In the first case (the one in the question), you are creating the object by yourself, rather than getting it from the Spring context. So Spring does not get a chance to <code>Autowire</code> the dependencies (which causes the <code>NullPointerException</code>). 

In the second case (the one in this answer), you get the bean from the Spring context and hence it is Spring managed and Spring takes care of <code>autowiring</code>.

blocks|key|2006428|text|Spring不再使用XML文件，而是大量使用注释。下面的示例是一个简单的独立Spring应用程序，它使用注释而不是XML文件。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2006429|package+com.zetcode.bean;

import+org.springframework.stereotype.Component;

@Component
public+class+Message+{

+++private+String+message+=+"Hello+there!";

+++public+void+setMessage(String+message){

++++++this.message++=+message;
+++}

+++public+String+getMessage(){

++++++return+message;
+++}
}|code-block|syntax|javascript|2006430|这是一个简单的bean。它使用@Component注释进行装饰，以便由Spring容器进行自动检测。|offset|length|style|CODE|2006431|package+com.zetcode.main;

import+com.zetcode.bean.Message;
import+org.springframework.beans.factory.annotation.Autowired;
import+org.springframework.context.ApplicationContext;
import+org.springframework.context.annotation.AnnotationConfigApplicationContext;
import+org.springframework.context.annotation.ComponentScan;

@ComponentScan(basePackages+=+"com.zetcode")
public+class+Application+{

++++public+static+void+main(String[]+args)+{

++++++++ApplicationContext+context
++++++++++++++++=+new+AnnotationConfigApplicationContext(Application.class);

++++++++Application+p+=+context.getBean(Application.class);
++++++++p.start();
++++}

++++@Autowired
++++private+Message+message;
++++private+void+start()+{
++++++++System.out.println("Message:+"+%2B+message.getMessage());
++++}
}|2006432|这是主要的Application类。@ComponentScan注释将搜索组件。@Autowired注释将bean注入到message变量中。AnnotationConfigApplicationContext用于创建Spring应用程序上下文。|2006433|我的Standalone+Spring+tutorial展示了如何创建同时包含XML和注解的独立Spring应用程序。|2006434|entityMap|0|LINK|mutability|MUTABLE|url|http://zetcode.com/articles/standalonespring/^0|0|0|F|A|0|0|5|B|I|E|14|A|1O|7|1Z|Y|0|2|Q|0|0^^$0|@$1|2|3|4|5|6|7|10|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|11|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|12|8|@$I|13|J|14|K|L]]|9|@]|A|$]]|$1|M|3|N|5|D|7|15|8|@]|9|@]|A|$E|F]]|$1|O|3|P|5|6|7|16|8|@$I|17|J|18|K|L]|$I|19|J|1A|K|L]|$I|1B|J|1C|K|L]|$I|1D|J|1E|K|L]|$I|1F|J|1G|K|L]]|9|@]|A|$]]|$1|Q|3|R|5|6|7|1H|8|@]|9|@$I|1I|J|1J|1|1K]]|A|$]]|$1|S|3|-4|5|6|7|1L|8|@]|9|@]|A|$]]]|T|$U|$5|V|W|X|A|$Y|Z]]]]

Spring is moving away from XML files and uses annotations heavily. The following example is a simple standalone Spring application which uses annotation instead of XML files.

<pre><code>package com.zetcode.bean;

import org.springframework.stereotype.Component;

@Component
public class Message {

 private String message = "Hello there!";

 public void setMessage(String message){

 this.message = message;
 }

 public String getMessage(){

 return message;
 }
}
</code></pre>

This is a simple bean. It is decorated with the <code>@Component</code> annotation for auto-detection by Spring container.

<pre><code>package com.zetcode.main;

import com.zetcode.bean.Message;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.ComponentScan;

@ComponentScan(basePackages = "com.zetcode")
public class Application {

 public static void main(String[] args) {

 ApplicationContext context
 = new AnnotationConfigApplicationContext(Application.class);

 Application p = context.getBean(Application.class);
 p.start();
 }

 @Autowired
 private Message message;
 private void start() {
 System.out.println("Message: " + message.getMessage());
 }
}
</code></pre>

This is the main <code>Application</code> class. The <code>@ComponentScan</code> annotation searches for components. The <code>@Autowired</code> annotation injects the bean into the <code>message</code> variable. The <code>AnnotationConfigApplicationContext</code> is used to create the Spring application context.

My <a href="http://zetcode.com/articles/standalonespring/" rel="noreferrer">Standalone Spring tutorial</a> shows how to create a standalone Spring application with both XML and annotations.

blocks|key|2006540|text|对于Spring4，使用Spring+Boot，我们可以在不使用直接从ApplicationContext获取Bean的反模式的情况下获得以下示例：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2006541|package+com.yourproject;

@SpringBootApplication
public+class+TestBed+implements+CommandLineRunner+{

++++private+MyService+myService;

++++@Autowired
++++public+TestBed(MyService+myService){
++++++++this.myService+=+myService;
++++}

++++public+static+void+main(String...+args)+{
++++++++SpringApplication.run(TestBed.class,+args);
++++}

++++@Override
++++public+void+run(String...+strings)+throws+Exception+{
++++++++System.out.println("myService:+"+%2B+MyService+);
++++}

}

@Service+
public+class+MyService{
++++public+String+getSomething()+{
++++++++return+"something";
++++}
}|code-block|syntax|javascript|2006542|确保所有注入的服务都在com.yourproject或其子包下。|offset|length|style|CODE|2006543|entityMap^0|0|0|B|F|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@$I|R|J|S|K|L]]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

For Spring 4, using Spring Boot we can have the following example without using the anti-pattern of getting the Bean from the ApplicationContext directly:

<pre><code>package com.yourproject;

@SpringBootApplication
public class TestBed implements CommandLineRunner {

 private MyService myService;

 @Autowired
 public TestBed(MyService myService){
 this.myService = myService;
 }

 public static void main(String... args) {
 SpringApplication.run(TestBed.class, args);
 }

 @Override
 public void run(String... strings) throws Exception {
 System.out.println("myService: " + MyService );
 }

}

@Service 
public class MyService{
 public String getSomething() {
 return "something";
 }
}
</code></pre>

Make sure that all your injected services are under <code>com.yourproject</code> or its subpackages.

blocks|key|1792996|text|一个很好的解决方案是执行以下操作，|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1792997|import+org.springframework.beans.BeansException;
import+org.springframework.context.ApplicationContext;
import+org.springframework.context.ApplicationContextAware;
import+org.springframework.stereotype.Component;

@Component
public+class+SpringContext+implements+ApplicationContextAware+{

private+static+ApplicationContext+context;

/**
+*+Returns+the+Spring+managed+bean+instance+of+the+given+class+type+if+it+exists.
+*+Returns+null+otherwise.
+*+@param+beanClass
+*+@return
+*/
public+static+<T+extends+Object>+T+getBean(Class<T>+beanClass)+{
++++return+context.getBean(beanClass);
}

@Override
public+void+setApplicationContext(ApplicationContext+context)+throws+BeansException+{

++++//+store+ApplicationContext+reference+to+access+required+beans+later+on
++++SpringContext.context+=+context;
}
}|code-block|syntax|javascript|1792998|然后你可以像这样使用它：|1792999|YourClass+yourClass+=+SpringContext.getBean(YourClass.class);|1793000|我在下面的网站上找到了这个非常好的解决方案：https://confluence.jaytaala.com/pages/viewpage.action?pageId=18579463|offset|length|1793001|entityMap|0|LINK|mutability|MUTABLE|url|https://confluence.jaytaala.com/pages/viewpage.action?pageId=18579463^0|0|0|0|0|M|1X|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|X|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Y|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|Z|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|10|8|@]|9|@$M|11|N|12|1|13]]|A|$]]|$1|O|3|-4|5|6|7|14|8|@]|9|@]|A|$]]]|P|$Q|$5|R|S|T|A|$U|V]]]]

A nice solution would be to do following,

<pre><code>import org.springframework.beans.BeansException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.stereotype.Component;

@Component
public class SpringContext implements ApplicationContextAware {

private static ApplicationContext context;

/**
 * Returns the Spring managed bean instance of the given class type if it exists.
 * Returns null otherwise.
 * @param beanClass
 * @return
 */
public static &lt;T extends Object&gt; T getBean(Class&lt;T&gt; beanClass) {
 return context.getBean(beanClass);
}

@Override
public void setApplicationContext(ApplicationContext context) throws BeansException {

 // store ApplicationContext reference to access required beans later on
 SpringContext.context = context;
}
}
</code></pre>

Then you can use it like:

<pre><code>YourClass yourClass = SpringContext.getBean(YourClass.class);
</code></pre>

I found this very nice solution in the following website: <a href="https://confluence.jaytaala.com/pages/viewpage.action?pageId=18579463" rel="nofollow noreferrer">https://confluence.jaytaala.com/pages/viewpage.action?pageId=18579463</a>

blocks|key|1793062|text|如果您运行的是SpringBoot：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1793063|我只是遇到了同样的问题，我无法从static+main方法中自动连接我的服务之一。|1793064|如果您依赖于SpringApplication.run，请参阅下面的方法|1793065|@SpringBootApplication
public+class+PricingOnlineApplication+{

++++@Autowired
++++OrchestratorService+orchestratorService;

++++public+static+void+main(String[]+args)+{
++++++++ConfigurableApplicationContext+context+=+SpringApplication.run(PricingOnlineApplication.class,+args);
++++++++PricingOnlineApplication+application+=+context.getBean(PricingOnlineApplication.class);

++++++++application.start();
++++}

++++private+void+start()+{
++++++++orchestratorService.performPricingRequest(null);
++++}

}|code-block|syntax|javascript|1793066|我注意到SpringApplication.run返回一个上下文，可以使用类似于上面描述的方法。从那里开始，它与上面完全相同;-)|1793067|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|P|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|Q|8|@]|9|@]|A|$]]|$1|F|3|G|5|H|7|R|8|@]|9|@]|A|$I|J]]|$1|K|3|L|5|6|7|S|8|@]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

I case you are running SpringBoot:

I just had the same problem, that I could not Autowire one of my services from the static main method.

See below an approach in case you are relying on SpringApplication.run:

<pre><code>@SpringBootApplication
public class PricingOnlineApplication {

 @Autowired
 OrchestratorService orchestratorService;

 public static void main(String[] args) {
 ConfigurableApplicationContext context = SpringApplication.run(PricingOnlineApplication.class, args);
 PricingOnlineApplication application = context.getBean(PricingOnlineApplication.class);

 application.start();
 }

 private void start() {
 orchestratorService.performPricingRequest(null);
 }

}
</code></pre>

I noticed that SpringApplication.run returns a context which can be used similar to the above described approaches. From there, it is exactly the same as above ;-)

Here is my code:

<pre><code>public class Main {

 public static void main(String[] args) {
 Main p = new Main();
 p.start(args);
 }

 @Autowired
 private MyBean myBean;
 private void start(String[] args) {
 ApplicationContext context = 
 new ClassPathXmlApplicationContext("META-INF/config.xml");
 System.out.println("my beans method: " + myBean.getStr());
 }
}

@Service 
public class MyBean {
 public String getStr() {
 return "string";
 }
}
</code></pre>

<hr>

<pre><code>&lt;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-3.0.xsd
 http://www.springframework.org/schema/context
 http://www.springframework.org/schema/context/spring-context-3.0.xsd"&gt; 
 &lt;context:annotation-config /&gt; 
 &lt;context:component-scan base-package="mypackage"/&gt;
&lt;/beans&gt;
</code></pre>

Why doesn't this work? I get <code>NullPointerException</code>. Is it possible to use autowiring in a standalone application?

Using Spring 3 autowire in a standalone Java application

Spring Boot

容器

下面是我的代码：public class Main {    public static void main(String[] args) {        Main p = new Main();        p.start(args);    }    @Autowired    private MyBean m...

问在独立的Java应用程序中使用Spring3自动线缆
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