Question

在@Service类中有几个用@Value注释的字段。这些字段未正确填充并且为空。也许我忽略了一些事情，我已经粘贴了下面的相关代码块。尝试了具有相同结果的替代选项env.getProperty（）。

输出中以下属性的值为null。

package com.project.service.impl;
import org.springframework.beans.factory.annotation.Value

@Service("aService")
@PropertySource(value="classpath:app.properties")
public class ServiceImpl implements Service{
    private Environment environment;
    @Value("${list.size}") 
    private Integer list1;

    @Value("${list2.size}") 
    private Integer list2Size;

    @Autowired 
    public ServiceImpl(StringRedisTemplate stringTemplate){
        this.stringTemplate = stringTemplate;
        logger.info("TESTING 123: "+list1);
    }
    // ...
}

@EnableWebMvc
@ComponentScan(basePackages =  {"com.project.service","..."})
@Configuration
public class ServletConfig extends WebMvcConfigurerAdapter {
    // ...
    @Bean
    public static PropertySourcesPlaceholderConfigurer properties() {
        PropertySourcesPlaceholderConfigurer propertyPlaceholderConfigurer = new PropertySourcesPlaceholderConfigurer();        
        Resource[] resources = new ClassPathResource[] {
            new ClassPathResource("app.properties")
        };
        propertyPlaceholderConfigurer.setLocations(resources);
        propertyPlaceholderConfigurer.setIgnoreUnresolvablePlaceholders(true);
        return propertyPlaceholderConfigurer;
    }
}

Answer 1

现场注入在构造之后发生，因此出现NullPointer异常。解决方案是使用@Value注释构造函数参数，例如

public ServiceImpl(StringRedisTemplate stringTemplate, @Value("${list.size}" Integer list1, ..){}

@Service类中的@Value属性为Null

1 个答案: