SpringBoot如何使用ApplicationContext獲取bean對象

第SpringBoot如何使用ApplicationContext獲取bean對象目錄使用ApplicationContext獲取bean對象SpringBootBean注入的深入研究下面代碼可正常運行下面代碼不能正常運行比較解決方案應(yīng)用

使用ApplicationContext獲取bean對象

編寫一個ApplicationContextFactory工廠類

publicclassApplicationContextFactory{

privatestaticApplicationContextapplicationContext=null;

publicstaticvoidsetApplicationContext(ApplicationContextapplicationContext)throwsBeansException{

applicationContext=applicationContext;

publicstaticApplicationContextgetApplicationContext(){

returnapplicationContext;

}

在SpringBoot的啟動類中設(shè)置ApplicationContext

publicclassApplication{

publicstaticvoidmain(String[]args){

ConfigurableApplicationContextapp=SpringApplication.run(Application.class,args);

ApplicationContextFactory.setApplicationContext(app);

通過ApplicationContextFactory獲取SpringApplication從而獲取bean對象

ApplicationContextapplicationContext=ApplicationContextFactory.getApplicationContext();

Clazzclazz=applicationContext.getBean(Clazz.class);

SpringBootBean注入的深入研究

下面代碼可正常運行

DemoService

@Service

publicclassDemoService{

publicvoidsave(){

System.out.println("DemoServicesave");

}

CommonClass

@Component

publicclassCommonClass{

@Resource

privateDemoServicedemoService;

publicvoidfun(){

System.out.println("fun");

demoService.save();

Controller

@Resource

privateCommonClasscommonClass;

@ResponseBody

@GetMapping("/fun")

publicvoidfun(){

commonClass.fun();

下面代碼不能正常運行

DemoService

@Service

publicclassDemoService{

publicvoidsave(){

System.out.println("DemoServicesave");

}

CommonClass

publicclassCommonClass{

@Resource

privateDemoServicedemoService;

publicvoidfun(){

System.out.println("fun");

demoService.save();

Controller

@ResponseBody

@GetMapping("/fun")

publicvoidfun(){

CommonClasscommonClass=newCommonClass();

commonClass.fun();

}

比較

比較兩個代碼發(fā)現(xiàn)后者與前者的區(qū)別：因后者的CommonClass沒有使用@Component標(biāo)注，所以在Controller中不能才用注入方式生成CommonClass對象，而是才用new的方式生成了該對象。

這樣一來，CommonClass對象是手工創(chuàng)建，所以在它內(nèi)部注入DemoService對象的代碼就錯誤了。

解決方案

新建工具類

@Component

publicclassApplicationContextUtilimplementsApplicationContextAware{

privatestaticApplicationContextact;

@Override

publicvoidsetApplicationContext(ApplicationContextapplicationContext)throwsBeansException{

act=applicationContext;

*根據(jù)bean的名字獲取工廠中對應(yīng)的bean對象

*@parambeanName

*@return

publicstaticObjectgetBean(StringbeanName){

returnact.getBean(beanName);

注：實際測試發(fā)現(xiàn)上面代碼中的static不能省略

DemoService

@Service

publicclassDemoService{

publicvoidsave(){

System.out.println("DemoServicesave");

}

CommonClass

publicclassCommonClass{

@Resource

privateDemoServicedemoService;

publicvoidfun(){

DemoServicedemoService=(DemoService)ApplicationContextUtil.getBean("demoService");

System.out.println("fun");

demoService.save();

此處不再采用注入的方式獲取DemoService對象，而是通過工具類的方式

Controller

@ResponseBody

@GetMapping("/fun")

publicvoidfun(){

CommonClasscommonClass=newCommonClass();

commonClass.fun();

}

再次運行程序，一切正常

應(yīng)用

在Sprin