项目启动初始化数据的方法

r囧r小猫 2023-02-28 11:20 46阅读 0赞

在开发过程中，可能有一些固定的数据比如字典表数据，可以在项目初始化时候获取并保存到常量类中，可以避免多次调用数据库。在项目启动时初始化数据有以下几种方法：

1、@PostConstruct注解：通过给方法名加上@PostConstruct注解，会在项目初始化时执行：

@Compant
    public class Demo{
     
        @PostConstruct
        public void init(){
            //项目启动执行方法
            
        }
    }

2、在配置文件注入bean的地方添加init-method方法：这种方法会在注入bean到容器时，主动去调用init-method指定的方法，一般用在spring项目中：

3、实现InitializingBean接口，复写afterPropertiesSet方法，如：

package com.mydemo.config;
    
    import com.mydemo.service.AreaService;
    import org.springframework.beans.factory.InitializingBean;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.stereotype.Component;
    
    import java.util.List;
    
    @Component
    public class InitDemo implements InitializingBean {
        @Autowired
        private AreaService areaService;
    
        @Override
        public void afterPropertiesSet() throws Exception {
            List<String> list = areaService.getProvinceList();
            System.out.println(list.size());
        }
    }

4、在ApplicationContextAware实现类中初始化，如：

package com.mydemo.config;
    
    import org.springframework.context.ApplicationContext;
    import org.springframework.context.support.ClassPathXmlApplicationContext;
    
    
    public class DefaultBeanFactory {
    	private static ApplicationContext context = null;
    	private static DefaultBeanFactory instance = null;
    	private static Object lock = new Object();
    
    	private DefaultBeanFactory(String filepath){
    		try {
    			context = new ClassPathXmlApplicationContext(filepath);
    		} catch (Exception e) {
    		}
    	}
    	@SuppressWarnings("static-access")
    	private DefaultBeanFactory(ApplicationContext context){
    		try {
    			this.context = context;
    		} catch (Exception e) {
    		}
    	}
    
    	public static void setSpringApplicationContext(ApplicationContext context){
    		synchronized (lock) {
    			instance = new DefaultBeanFactory(context);
    		}
    	}
    	public static DefaultBeanFactory getInstance() {
    		if(instance == null || context == null){
    			throw new RuntimeException("Spring context is null!");
    		}
    		return instance;
    	}
    
    	public static DefaultBeanFactory getInstance(String filepath) {
    		synchronized (lock) {
    			instance = new DefaultBeanFactory(filepath);
    		}
    		return instance;
    	}
    	public Object getBean(String name) {
    		return context.getBean(name);
    	}
    }

package com.mydemo.config;
    
    
    import com.mydemo.service.AreaService;
    import org.slf4j.Logger;
    import org.slf4j.LoggerFactory;
    import org.springframework.beans.BeansException;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.context.ApplicationContext;
    import org.springframework.context.ApplicationContextAware;
    import org.springframework.stereotype.Component;
    
    import java.util.List;
    
    
    @Component
    public class ApplicationContextRegister implements ApplicationContextAware {
        private static Logger logger = LoggerFactory.getLogger(ApplicationContextRegister.class);
        private static ApplicationContext APPLICATION_CONTEXT;
    
        @Autowired
        private AreaService areaService;
        /**
         * 设置spring上下文
         * @param applicationContext spring上下文
         * @throws BeansException
         * */
        @Override
        public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
            logger.debug("ApplicationContext registed-->{}", applicationContext);
            DefaultBeanFactory.setSpringApplicationContext(applicationContext);
    
            List<String> list = areaService.getProvinceList();
            System.out.println("长度"+list.size());
    
            APPLICATION_CONTEXT = applicationContext;
        }
    
        /**
         * 获取容器
         * @return
         */
        public static ApplicationContext getApplicationContext() {
            return APPLICATION_CONTEXT;
        }
    
        /**
         * 获取容器对象
         * @param type
         * @param <T>
         * @return
         */
        public static <T> T getBean(Class<T> type) {
            return APPLICATION_CONTEXT.getBean(type);
        }
    }

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