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This article is about how Spring gets beans in code. Xiaobian thinks it is quite practical, so share it with everyone for reference. Let's follow Xiaobian and have a look.

method is as follows

Method 1: Method 2: Obtaining ApplicationContext object through utils class provided by Spring Method 3: Inheriting from abstract class ApplicationObjectSupport Method 4: Inheriting from abstract class WebApplicationObjectSupport Method 5: Implementing interface ApplicationContextAware Method 6: Obtaining ApplicationContext object through utils class provided by Spring

Summary of ways to get beans in spring:

Method 1: Reflect objects by reading XML files

ApplicationContext ac = new FileSystemXmlApplicationContext("applicationContext.xml");ac.getBean("userService");//Compare:

Note: This approach applies to standalone applications that use the Spring framework and require the program to manually initialize Spring through configuration files.

Method 2: Obtain ApplicationContext object through tool class provided by Spring

ApplicationContext ac1 = WebApplicationContextUtils.getRequiredWebApplicationContext(ServletContext sc);ApplicationContext ac2 = WebApplicationContextUtils.getWebApplicationContext(ServletContext sc);ac1.getBean("beanId");ac2.getBean("beanId");

Description: This method is suitable for B/S system of Spring framework, and obtains ApplicationContext object through ServletContext object. Then get the required class instance through it. The difference between the two tools is that the former throws an exception when a fetch fails. The latter returns null.

Method 3: Inherited from abstract class ApplicationObjectSupport

Description: The abstract class ApplicationObjectSupport provides getApplicationContext() method. It is easy to get the ApplicationContext.

Spring is initialized. ApplicationContext objects are injected through the abstract class's setApplicationContext(ApplicationContext) method.

Method 4: Inherited from abstract class WebApplicationObjectSupport

Note: Similar to the above method. Call getWebApplicationContext() to get WebApplicationContext

Method 5: Implement the interface ApplicationContextAware

Description: Implement the setApplicationContext(ApplicationContext) method of this interface, and save the ApplicationContext object. When Spring initializes, ApplicationContext objects are injected through this method.

Here is the code for implementing the ApplicationContextAware interface, similar to the first two methods:

public class SpringContextUtil implements ApplicationContextAware { // Spring applicationContext private static ApplicationContext applicationContext; /** * Callback methods that implement the ApplicationContextAware interface. Setting Context * * @param applicationContext */ public void setApplicationContext(ApplicationContext applicationContext) { SpringContextUtil.applicationContext = applicationContext; } /** * @return ApplicationContext */ public static ApplicationContext getApplicationContext() { return applicationContext; } /** * Get Object * * @param name * @return Object * @throws BeansException */ public static Object getBean(String name) throws BeansException { return applicationContext.getBean(name); } }

Although the last three methods provided by Spring can be implemented in ordinary classes to inherit or implement corresponding classes or interfaces to obtain Spring ApplicationContext objects, it is important to note that ordinary java classes that implement these classes or interfaces must be configured in Spring's configuration file applicationContext.xml. Otherwise, the retrieved ApplicationContext object will be null.

Method 6: ContextLoader via Spring

WebApplicationContext wac = ContextLoader.getCurrentWebApplicationContext();wac.getBean(beanID);

Finally, we provide a way to do this without servlets and without injection. One thing to note is that when the server starts up. Spring container initialization, you can not get the Spring container through the following method, details can be seen in the spring source code org.springframework.web.context.ContextLoader

ContextLoader.getCurrentWebApplicationContext()=NULL when JUNIT tests

Add the following code to the JUNIT test method, not used in the formal environment

MockServletContext sc = new MockServletContext("");sc.addInitParameter(ContextLoader.CONFIG_LOCATION_PARAM, "/applicationContext.xml");ServletContextListener listener = new ContextLoaderListener();ServletContextEvent event = new ServletContextEvent(sc);listener.contextInitialized(event);

Thank you for reading! About "Spring in the code how to get beans" this article is shared here, I hope the above content can have some help for everyone, so that we can learn more knowledge, if you think the article is good, you can share it to let more people see it!

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