Spring boot在普通类中使用service、dao层中的类，只需三步

痛定思痛。 2022-02-28 02:58 337阅读 0赞

在一个web项目的jsp中想要使用service中的一个类来获取数据库中的数据，但是用完之后报错说是空指针异常，上网查了之后总结了一下解决办法，只需三步。

##### 1、写一个工具类 SpringUtil #####

package com.shop.util;
    
    import org.springframework.beans.BeansException;
    import org.springframework.context.ApplicationContext;
    import org.springframework.context.ApplicationContextAware;
    
    public final class SpringUtil implements ApplicationContextAware {
    	private static ApplicationContext applicationContext = null;
    
    	@Override
    	public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
    		// TODO Auto-generated method stub
    		if (SpringUtil.applicationContext == null) {
    			SpringUtil.applicationContext = applicationContext;
    			System.out.println(
    					"========ApplicationContext配置成功,在普通类可以通过调用ToolSpring.getAppContext()获取applicationContext对象,applicationContext="
    							+ applicationContext + "========");
    		}
    	}
    	
    	public static ApplicationContext getApplicationContext() {
    		return applicationContext;
    	}
    	
    	//通过
    	public static Object getBean(String name) {
    		return getApplicationContext().getBean(name);
    	}
    	
    	//通过class获取Bean.
        public static <T> T getBean(Class<T> clazz){
               return getApplicationContext().getBean(clazz);
        }
    }

##### 2、在Application启动类中将工具类导入，不然依然无法使用 #####

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2tfeW91bmcxOTk3_size_16_color_FFFFFF_t_70]

##### 3、在ApplicationTests测试类中调用 #####

package com.shop.JZShop;
    
    import org.junit.Test;
    import org.junit.runner.RunWith;
    import org.springframework.boot.test.context.SpringBootTest;
    import org.springframework.test.context.junit4.SpringRunner;
    
    import com.shop.serviceImpl.GoodsServiceImpl;
    import com.shop.util.SpringUtil;
    
    @RunWith(SpringRunner.class)
    @SpringBootTest
    public class JzShopApplicationTests {
    	
    
    	@Test
    	public void contextLoads() {
    		//GoodsServiceImpl为我想要获取的service层中的类
    		GoodsServiceImpl goodsServiceImpl = (GoodsServiceImpl)SpringUtil.getBean(GoodsServiceImpl.class);
    		System.out.println(goodsServiceImpl.getGoodsByID(27).getGoodsName());
    	}
    }

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