2023-08-23 Spring加载问题

起因

写了一个缓存，这个缓存不会变动，我在final中加载，发现报错了。

 private final Map<Integer,String> companyMap;

    {
        departmentMap =  departmentService.list().stream()
                .collect(Collectors.toMap(DepartmentEntity::getId, DepartmentEntity::getName));

        companyMap = companyService.list().stream()
            .collect(Collectors.toMap(Company::getId, Company::getName));
    } 

代码报错 org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'jobPositionController': Unsatisfied dependency expressed through field 'jobPositionService'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'jobPositionService' defined in file [E:\Team Garde\team-garden-backend\target\classes\io\renren\modules\position\service\impl\JobPositionServiceImpl.class]: Instantiation of bean failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [io.renren.modules.position.service.impl.JobPositionServiceImpl]: Constructor threw exception; nested exception is java.lang.NullPointerException

解决

作为一个对Spring熟知的男人，我一眼就看出了问题所在，原因是在 JobPositionServiceImpl 的构造函数中使用了 departmentService 或 companyService，而这两个依赖的 bean 没有正确地注入，导致调用它们的方法时出现了空指针异常。
OK，我秒解决了这个问题

    private final Map<Integer,String> departmentMap;

    private final Map<Integer,String> companyMap;

    @Autowired
    public JobPositionServiceImpl(DepartmentService departmentService, CompanyService companyService) {
        this.departmentService = departmentService;
        this.companyService = companyService;
        this.departmentMap = initDepartmentMap();
        this.companyMap = initCompanyMap();
    }

    private Map<Integer, String> initDepartmentMap() {
        return departmentService.list().stream()
                .collect(Collectors.toMap(DepartmentEntity::getId, DepartmentEntity::getName));
    }

    private Map<Integer, String> initCompanyMap() {
        return companyService.list().stream()
                .collect(Collectors.toMap(Company::getId, Company::getName));
    }

问题解决，继续写业务代码

后续

在开发中可能遇到各种问题，但是你只要拥有对源码的理解，毛毛雨啦~~~
哈哈哈，皮一下 ！
我们日常开发，一定要停下一点时间，看看Spring源码，你会发现你的职业生涯就像开挂一样！ 什么 Mybatis，什么 Lucene，只要怼着官方手册，就是一梭子的事情。
向Spring的开发人员致敬！！！

最后：
TEAM GARDEN ！！！ 加油 ！！！