SpringBoot使用ApplicationContext.getBean启动报空指针处理记录

最新推荐文章于 2024-12-10 19:59:37 发布

原创最新推荐文章于 2024-12-10 19:59:37 发布 · 819 阅读

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文章标签：

#spring boot #java #后端

问题：项目启动报空指针

定位：新增filter中init方法使用getbean控制

解决：在新增filter上加注解

@DependsOn({"applicationContextUtils"})

@Component
@DependsOn({"applicationContextUtils"})//此处解决空指针问题
public class XssFilter implements Filter{
    @Autowired
    private MultipartResolver multipartResolver=null;

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        //注入bean
        multipartResolver=(MultipartResolver) ApplicationContextUtils.getApplicationContext().getBean("multipartResolver",MultipartResolver.class);
    }
}

package com.bonc.ds.web.utils;

import org.springframework.beans.BeansException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.context.annotation.Configuration;

import java.util.Locale;

//对Spring容器进行各种上下文操作的工具类
@Configuration
public class ApplicationContextUtils implements ApplicationContextAware {

    private static ApplicationContext context;

    @Override
    public void setApplicationContext(ApplicationContext context) throws BeansException {
        ApplicationContextUtils.context = context;
    }

    public static ApplicationContext getApplicationContext(){
        return context;
    }
    //根据Bean名称获取Bean对象
    public static Object getBean(String beanName){
        return context.getBean(beanName);
    }

    public static Object getMassage(String key){
        return context.getMessage(key, null, Locale.getDefault());
    }
}

分析:

ApplicationContextUtils是否在Configuration的Bean初始化之前初始化是未知的。

用到的@DependsOn注解，先把SpringContextUtils注册到Spring容器里面

注解含义就是组件A要依赖于另一个组件B，也就是说被依赖的组件B会比组件A先注册到Spring容器中