我应该如何在SpringBoot中使用JpaRepository.findOne（）？

Question

我刚刚通过阅读《Spring Boot in Action》一书开始学习Spring Boot，并且正在学习本书的示例，尝试自己运行它们，但是使用时遇到了问题JpaRepository.findOne()。我遍历了本章以查找可能的不匹配之处。但是，它根本不起作用。该项目应该是一个简单的阅读清单。这是代码：Jpa界面：package com.lixin.readinglist;import org.springframework.data.jpa.repository.JpaRepository;/** * @author lixin */public interface ReaderRepository extends JpaRepository<Reader, String> {}SecurityConfig：package com.lixin.readinglist;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.context.annotation.Configuration;import org.springframework.security.config.annotation.authentication.builders.AuthenticationManagerBuilder;import org.springframework.security.config.annotation.web.builders.HttpSecurity;import org.springframework.security.config.annotation.web.configuration.EnableWebSecurity;import org.springframework.security.config.annotation.web.configuration.WebSecurityConfigurerAdapter;import org.springframework.security.core.userdetails.UserDetailsService;/** * @author lixin */@Configuration@EnableWebSecuritypublic class SecurityConfig extends WebSecurityConfigurerAdapter {    private final ReaderRepository readerRepository;    @Autowired    public SecurityConfig(ReaderRepository readerRepository) {        this.readerRepository = readerRepository;    }而且我不断收到此错误：Error:(40, 86) java: method findOne in interface org.springframework.data.repository.query.QueryByExampleExecutor<T> cannot be applied to given types;  required: org.springframework.data.domain.Example<S>  found: java.lang.String  reason: cannot infer type-variable(s) S    (argument mismatch; java.lang.String cannot be converted to org.springframework.data.domain.Example<S>)

Answer 1

您可以使用findById，而不是findOne，findOne需要一个示例对象，您可以在此处查找更多信息