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  • 依赖Spring的情况下,Java Web项目如何在启动时加载数据库中的数据?

    原文:https://blog.csdn.net/u012345283/article/details/39558537

    原文:https://blog.csdn.net/wandrong/article/details/44782627

    我的尝试:

    1、继承HttpServlet,在web.xml中配置servlet的<load-on-startup>1</load-on-startup>,项目启动时globalParaService被注入了,但是跟踪到init方法里面,globalParaService为null。(失败)

    public class InitSysServlet extends HttpServlet {
    
        private SysGlobalParaServiceI globalParaService;
        
        @Autowired
        public void setGlobalParaService(SysGlobalParaServiceI globalParaService) {
            this.globalParaService = globalParaService;
        }
    
        @Override
        public void init(ServletConfig config) throws ServletException {
            super.init(config);
            
            SysGlobalPara codeRule = globalParaService.getCodeRule();
            if (null != codeRule) {
                SystemConfig.IS_SET_WIZADED = "true".equals(codeRule.getSysValue());
            } else {
                SystemConfig.IS_SET_WIZADED = false;
            }
            
        }
    }

    然后,我试着手动创建globalParaService,代码调整为

    public class InitSysServlet extends HttpServlet {
    
        @Override
        public void init(ServletConfig config) throws ServletException {
            super.init(config);
            
            SysGlobalParaServiceI globalParaService = new SysGlobalParaServiceImpl();
            SysGlobalPara codeRule = globalParaService.getCodeRule();
            if (null != codeRule) {
                SystemConfig.IS_SET_WIZADED = "true".equals(codeRule.getSysValue());
            } else {
                SystemConfig.IS_SET_WIZADED = false;
            }
            
        }
    }

    然而,SysGlobalParaServiceImpl里面依赖的其他由Spring注入的对象为null。

    搞不定了,百度到以上两篇文章,根据上面文章进行尝试都成功了。

    2、直接在init方法中获取Spring的bean (成功)

    首先在Spring配置文件中配置SysGlobalParaServiceImpl类对应的bean,然后在代码中获取,最终代码如下:

    public class InitSysServlet extends HttpServlet {
    
        private SysGlobalParaServiceI globalParaService;
        
        @Override
        public void init(ServletConfig config) throws ServletException {
            super.init(config);
            
            WebApplicationContext wac = ContextLoader.getCurrentWebApplicationContext();          
            globalParaService = (SysGlobalParaServiceI) wac.getBean("gpservice");
    
            SysGlobalPara codeRule = globalParaService.getCodeRule();
            if (null != codeRule) {
                SystemConfig.IS_SET_WIZADED = "true".equals(codeRule.getSysValue());
            } else {
                SystemConfig.IS_SET_WIZADED = false;
            }
        }
    }

    以下两种则与servlet无关,而是继承spring提供的接口。

    3、实现Spring的接口InitializingBean,则实现类在被Sping初始化之后,会调用其中的afterPropertiesSet方法,代码如下:

    @Component
    public class InitSysServlet implements InitializingBean {
    
        private SysGlobalParaServiceI globalParaService;
        
        @Autowired
        public void setGlobalParaService(SysGlobalParaServiceI globalParaService) {
            this.globalParaService = globalParaService;
        }
    
        @Override
        public void afterPropertiesSet() throws Exception {
            SysGlobalPara codeRule = globalParaService.getCodeRule();
            if (null != codeRule) {
                SystemConfig.IS_SET_WIZADED = "true".equals(codeRule.getSysValue());
            } else {
                SystemConfig.IS_SET_WIZADED = false;
            }
        }
    
    
    }

    4、实现Spring的接口ApplicationListener<ContextRefreshedEvent>,在所有的bean初始化之后会调用其中的方法onApplicationEvent,代码如下:

    @Component
    public class InitSysServlet implements ApplicationListener<ContextRefreshedEvent> {
    
        private SysGlobalParaServiceI globalParaService;
        
        @Autowired
        public void setGlobalParaService(SysGlobalParaServiceI globalParaService) {
            this.globalParaService = globalParaService;
        }
    
        @Override
        public void onApplicationEvent(ContextRefreshedEvent arg0) {
            SysGlobalPara codeRule = globalParaService.getCodeRule();
            if (null != codeRule) {
                SystemConfig.IS_SET_WIZADED = "true".equals(codeRule.getSysValue());
            } else {
                SystemConfig.IS_SET_WIZADED = false;
            }
        }
    
    }

    最后,我采用的是第4中,实现Spring的接口ApplicationListener<ContextRefreshedEvent>。

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  • 原文地址:https://www.cnblogs.com/yarightok/p/9765791.html
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