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Spring-Data-Jpa使用总结

Spring-Data-Jpa使用总结

作者: 逸竹小站 | 来源:发表于2019-10-17 10:16 被阅读0次

    参考资源列表

    1. 官方文档:https://docs.spring.io/spring-data/jpa/docs/2.1.5.RELEASE/reference/html/
    2. 《Spring Data JPA入门到精通》

    前言

    JPAJava Persistence API的简称,是SpringHibernate的基础上进行的二次封装框架,为了更好更方便的融入Spring大家庭,同时也提供了一些Hibernate没有的特性,与其他ORM框架一起构成SpringData,统一封装了ORM层,使开发人员使用起来更加方便快捷。

    备注:本文所有代码都是基于SpringBoot 2.1.5版本

    JPA的使用

    基本单表操作的使用

    对于操作单表来说,jpa提供了非常方便使用的封装,我们只需要按规范编写Repository接口同时继承JpaRepository就可以享用jpa基本功能了。代码如下:

    User实体:

    package com.yizhu.entity;
    
    import lombok.Builder;
    import lombok.Data;
    import lombok.ToString;
    
    import javax.persistence.*;
    import java.io.Serializable;
    import java.util.List;
    import java.util.Set;
    
    @Entity
    @Table(name = "t_user")
    @Data
    @Builder
    public class User implements Serializable {
    
        private static final long serialVersionUID = 1L;
    
        @Id
        @GeneratedValue(strategy = GenerationType.IDENTITY)
        private Long id;
    
        private String name;
    
        private String password;
    
        private Integer age;
    
        private Integer sex;
    }
    
    

    repository接口:

    package com.yizhu.repository;
    
    import com.yizhu.entity.User;
    
    public interface UserRepository extends JpaRepository<User, Long>{
    }
    

    下面看看jpa为我们提供了哪些默认操作单表数据的方法

    package org.springframework.data.jpa.repository;
    @NoRepositoryBean
    public interface JpaRepository<T, ID> extends PagingAndSortingRepository<T, ID>, QueryByExampleExecutor<T> {
        List<T> findAll(); // 查询全表数据
    
        List<T> findAll(Sort var1); // 查询全表数据,支持排序
    
        List<T> findAllById(Iterable<ID> var1); // 根据id字段查询所有匹配数据
    
        <S extends T> List<S> saveAll(Iterable<S> var1); // 批量保存或更新数据
    
        void flush(); // 刷新本地缓存到数据库
    
        <S extends T> S saveAndFlush(S var1); // 保存或更新单挑数据及刷新本地缓存到数据库
    
        void deleteInBatch(Iterable<T> var1); // 批量删除数据
    
        void deleteAllInBatch(); // 批量删除全表数据
    
        T getOne(ID var1); // 根据id查询一条匹配数据
    
        <S extends T> List<S> findAll(Example<S> ar1); // Example方式的查询指定实体
    
        <S extends T> List<S> findAll(Example<S> var1, Sort var2);  // Example方式的查询指定实体并排序
    }
    
    package org.springframework.data.repository;
    @NoRepositoryBean
    public interface PagingAndSortingRepository<T, ID> extends CrudRepository<T, ID> {
        Iterable<T> findAll(Sort var1);  // 根据排序查询全表,返回类型是任意集合
    
        Page<T> findAll(Pageable var1); // 根据分页参数分页查询
    }
    
    package org.springframework.data.repository;
    @NoRepositoryBean
    public interface CrudRepository<T, ID> extends Repository<T, ID> {
        <S extends T> S save(S var1);   // 保存或更新单条数据
    
        <S extends T> Iterable<S> saveAll(Iterable<S> var1);  // 批量保存或更新
    
        Optional<T> findById(ID var1);  // 根据id查询数据,返回类型是Optional
    
        boolean existsById(ID var1);    // 根据id判断数据是否存在
    
        Iterable<T> findAll(); // 查询全表数据,返回类型为集合
    
        Iterable<T> findAllById(Iterable<ID> var1); // 根据id集合查询数据
    
        long count();   // 统计全表数据量
    
        void deleteById(ID var1); // 根据id删除数据
    
        void delete(T var1);    // 删除单条数据
    
        void deleteAll(Iterable<? extends T> var1);     // 删除指定集合数据
    
        void deleteAll();   // 删除全表数据
    }
    
    package org.springframework.data.repository.query;
    public interface QueryByExampleExecutor<T> {
        <S extends T> Optional<S> findOne(Example<S> var1); // 根据Example查询一条
    
        <S extends T> Iterable<S> findAll(Example<S> var1); // 根据Example查询所有数据
    
        <S extends T> Iterable<S> findAll(Example<S> var1, Sort var2);  // 根据Example查询所有数据,并排序
    
        <S extends T> Page<S> findAll(Example<S> var1, Pageable var2);  // 根据Example分页查询
    
        <S extends T> long count(Example<S> var1);  // 根据Example统计
    
        <S extends T> boolean exists(Example<S> var1);  // 根据Example判断数据是否存在
    }
    

    除此之外,jpa提供了一套新的生成sql的机制,非常方便好用,jpa根据Repository接口的方法中的关键字、实体字段及出入参,自动生成sql,这种方式启动容器的时候就可以检查语法是否正确,简单使用例子如下:

    package com.yizhu.repository;
    
    import com.yizhu .entity.User;
    import org.springframework.data.jpa.repository.EntityGraph;
    import org.springframework.data.jpa.repository.JpaRepository;
    import org.springframework.data.jpa.repository.JpaSpecificationExecutor;
    import org.springframework.data.jpa.repository.Query;
    import org.springframework.data.repository.query.Param;
    
    import java.util.List;
    
    public interface UserRepository extends JpaRepository<User, Long>{
    
        /**
         * 根据年龄查询用户信息
         * @param age
         * @return
         */
        List<User> findAllByAge(Integer age);
    
        /**
         * 根据用户性别和所属组织名称查询用户信息
         * @param userSex
         * @param orgName
         * @return
         */
        List<User> findBySexAndOrg(@Param("sex") Integer sex, @Param("name") String name);
    
        /**
         * 根据用户名模糊查询
         * @return
         */
        List<User> findAllByNameLike(@Param("name") String name);
    }
    

    除了findByAnd之外,还有一些关键词,全部定义在PartTreePart类,组装起来可以生成各种各样的sql,下面截取部分代码,感兴趣的同学可以打开源码去阅读

    package org.springframework.data.repository.query.parser;
    public class PartTree implements Streamable<PartTree.OrPart> {
        private static final String KEYWORD_TEMPLATE = "(%s)(?=(\\p{Lu}|\\P{InBASIC_LATIN}))";
        private static final String QUERY_PATTERN = "find|read|get|query|stream";
        private static final String COUNT_PATTERN = "count";
        private static final String EXISTS_PATTERN = "exists";
        private static final String DELETE_PATTERN = "delete|remove";
        private static final Pattern PREFIX_TEMPLATE = Pattern.compile("^(find|read|get|query|stream|count|exists|delete|remove)((\\p{Lu}.*?))??By");
        private final PartTree.Subject subject;
        private final PartTree.Predicate predicate;
        ...
        private static String[] split(String text, String keyword) {
            Pattern pattern = Pattern.compile(String.format("(%s)(?=(\\p{Lu}|\\P{InBASIC_LATIN}))", keyword));
            return pattern.split(text);
        }
    
        private static class Predicate implements Streamable<PartTree.OrPart> {
            private static final Pattern ALL_IGNORE_CASE = Pattern.compile("AllIgnor(ing|e)Case");
            private static final String ORDER_BY = "OrderBy";
            private final List<PartTree.OrPart> nodes;
            private final OrderBySource orderBySource;
            private boolean alwaysIgnoreCase;
    
            public Predicate(String predicate, Class<?> domainClass) {
                String[] parts = PartTree.split(this.detectAndSetAllIgnoreCase(predicate), "OrderBy");
                if (parts.length > 2) {
                    throw new IllegalArgumentException("OrderBy must not be used more than once in a method name!");
                } else {
                    this.nodes = (List)Arrays.stream(PartTree.split(parts[0], "Or")).filter(StringUtils::hasText).map((part) -> {
                        return new PartTree.OrPart(part, domainClass, this.alwaysIgnoreCase);
                    }).collect(Collectors.toList());
                    this.orderBySource = parts.length == 2 ? new OrderBySource(parts[1], Optional.of(domainClass)) : OrderBySource.EMPTY;
                }
            }
            ...
        }
    
        private static class Subject {
            private static final String DISTINCT = "Distinct";
            private static final Pattern COUNT_BY_TEMPLATE = Pattern.compile("^count(\\p{Lu}.*?)??By");
            private static final Pattern EXISTS_BY_TEMPLATE = Pattern.compile("^(exists)(\\p{Lu}.*?)??By");
            private static final Pattern DELETE_BY_TEMPLATE = Pattern.compile("^(delete|remove)(\\p{Lu}.*?)??By");
            private static final String LIMITING_QUERY_PATTERN = "(First|Top)(\\d*)?";
            private static final Pattern LIMITED_QUERY_TEMPLATE = Pattern.compile("^(find|read|get|query|stream)(Distinct)?(First|Top)(\\d*)?(\\p{Lu}.*?)??By");
            private final boolean distinct;
            private final boolean count;
            private final boolean exists;
            private final boolean delete;
            private final Optional<Integer> maxResults;
    
            public Subject(Optional<String> subject) {
                this.distinct = (Boolean)subject.map((it) -> {
                    return it.contains("Distinct");
                }).orElse(false);
                this.count = this.matches(subject, COUNT_BY_TEMPLATE);
                this.exists = this.matches(subject, EXISTS_BY_TEMPLATE);
                this.delete = this.matches(subject, DELETE_BY_TEMPLATE);
                this.maxResults = this.returnMaxResultsIfFirstKSubjectOrNull(subject);
            }
    
            private Optional<Integer> returnMaxResultsIfFirstKSubjectOrNull(Optional<String> subject) {
                return subject.map((it) -> {
                    Matcher grp = LIMITED_QUERY_TEMPLATE.matcher(it);
                    return !grp.find() ? null : StringUtils.hasText(grp.group(4)) ? Integer.valueOf(grp.group(4)) : 1;
                });
            }
            ...
    
            private boolean matches(Optional<String> subject, Pattern pattern) {
                return (Boolean)subject.map((it) -> {
                    return pattern.matcher(it).find();
                }).orElse(false);
            }
        }
    }
    
    package org.springframework.data.repository.query.parser;
    public class Part {
        private static final Pattern IGNORE_CASE = Pattern.compile("Ignor(ing|e)Case");
        private final PropertyPath propertyPath;
        private final Part.Type type;
        private Part.IgnoreCaseType ignoreCase;
        ...
        public static enum Type {
            BETWEEN(2, new String[]{"IsBetween", "Between"}),
            IS_NOT_NULL(0, new String[]{"IsNotNull", "NotNull"}),
            IS_NULL(0, new String[]{"IsNull", "Null"}),
            LESS_THAN(new String[]{"IsLessThan", "LessThan"}),
            LESS_THAN_EQUAL(new String[]{"IsLessThanEqual", "LessThanEqual"}),
            GREATER_THAN(new String[]{"IsGreaterThan", "GreaterThan"}),
            GREATER_THAN_EQUAL(new String[]{"IsGreaterThanEqual", "GreaterThanEqual"}),
            BEFORE(new String[]{"IsBefore", "Before"}),
            AFTER(new String[]{"IsAfter", "After"}),
            NOT_LIKE(new String[]{"IsNotLike", "NotLike"}),
            LIKE(new String[]{"IsLike", "Like"}),
            STARTING_WITH(new String[]{"IsStartingWith", "StartingWith", "StartsWith"}),
            ENDING_WITH(new String[]{"IsEndingWith", "EndingWith", "EndsWith"}),
            IS_NOT_EMPTY(0, new String[]{"IsNotEmpty", "NotEmpty"}),
            IS_EMPTY(0, new String[]{"IsEmpty", "Empty"}),
            NOT_CONTAINING(new String[]{"IsNotContaining", "NotContaining", "NotContains"}),
            CONTAINING(new String[]{"IsContaining", "Containing", "Contains"}),
            NOT_IN(new String[]{"IsNotIn", "NotIn"}),
            IN(new String[]{"IsIn", "In"}),
            NEAR(new String[]{"IsNear", "Near"}),
            WITHIN(new String[]{"IsWithin", "Within"}),
            REGEX(new String[]{"MatchesRegex", "Matches", "Regex"}),
            EXISTS(0, new String[]{"Exists"}),
            TRUE(0, new String[]{"IsTrue", "True"}),
            FALSE(0, new String[]{"IsFalse", "False"}),
            NEGATING_SIMPLE_PROPERTY(new String[]{"IsNot", "Not"}),
            SIMPLE_PROPERTY(new String[]{"Is", "Equals"});
    
            private static final List<Part.Type> ALL = Arrays.asList(IS_NOT_NULL, IS_NULL, BETWEEN, LESS_THAN, LESS_THAN_EQUAL, GREATER_THAN, GREATER_THAN_EQUAL, BEFORE, AFTER, NOT_LIKE, LIKE, STARTING_WITH, ENDING_WITH, IS_NOT_EMPTY, IS_EMPTY, NOT_CONTAINING, CONTAINING, NOT_IN, IN, NEAR, WITHIN, REGEX, EXISTS, TRUE, FALSE, NEGATING_SIMPLE_PROPERTY, SIMPLE_PROPERTY);
            public static final Collection<String> ALL_KEYWORDS;
            private final List<String> keywords;
            private final int numberOfArguments;
            ...
            static {
                List<String> allKeywords = new ArrayList();
                Iterator var1 = ALL.iterator();
    
                while(var1.hasNext()) {
                    Part.Type type = (Part.Type)var1.next();
                    allKeywords.addAll(type.keywords);
                }
    
                ALL_KEYWORDS = Collections.unmodifiableList(allKeywords);
            }
        }
    }
    

    可以看到单表操作的大部分需求jpa都为我们提供了现成的实现,但也支持我们使用@Query注解自定义查询sql,方便有sql基础的同学使用,sql可控性强。

    package com.yizhu.repository;
    
    import com.yizhu .entity.User;
    import org.springframework.data.jpa.repository.EntityGraph;
    import org.springframework.data.jpa.repository.JpaRepository;
    import org.springframework.data.jpa.repository.JpaSpecificationExecutor;
    import org.springframework.data.jpa.repository.Query;
    import org.springframework.data.repository.query.Param;
    
    import java.util.List;
    
    public interface UserRepository extends JpaRepository<User, Long>{
    
        /**
         * 查询所有用户信息
         * @return
         */
        @Query(value = "from User u")
        List<User> findAll();
    
        /**
         * 根据年龄查询用户信息
         * @param age
         * @return
         */
        @Query(value = "select * from t_user u where u.user_age = ?1", nativeQuery = true)
        List<User> findAllByAge(Integer age);
    
        /**
         * 根据用户性别和所属组织名称查询用户信息
         * @param userSex
         * @param orgName
         * @return
         */
        @Query(value = "select u from User u left join u.org o where u.userSex = :userSex and o.orgName = :orgName")
        List<User> findUsersBySexAndOrg(@Param("userSex") Integer userSex, @Param("orgName") String orgName);
    
    }
    

    多表关联

    @OneToOne@OneToMany@ManyToOne@ManyToMany

    @Entity
    @Table(name = "t_user")
    @NamedEntityGraph(name = "User.findUsers", attributeNodes = {@NamedAttributeNode("jobs"), @NamedAttributeNode("roles")})
    @Data
    @Builder
    @NoArgsConstructor
    @AllArgsConstructor
    public class User implements Serializable {
    
        private static final long serialVersionUID = 1L;
    
        @ApiModelProperty(hidden = true)
        @Id
        @GeneratedValue(strategy = GenerationType.IDENTITY)
        private Long id;
    
        @ApiModelProperty(value = "用户名")
        @Column(name = "user_name")
        private String name;
    
        @ApiModelProperty(value = "用户密码")
        @Column(name = "user_password")
        private String password;
    
        @ApiModelProperty(value = "用户年龄")
        @Column(name = "user_age")
        private Integer age;
    
        @ApiModelProperty(value = "用户性别")
        @Column(name = "user_sex")
        private Integer sex;
    
        @ApiModelProperty(value = "所属组织id")
        @Column(name = "org_id")
        private Long orgId;
    
        @ApiModelProperty(value = "用户信息")
        @OneToOne
        @JoinColumn(name = "id", updatable = false, insertable = false)
        private UserInfo userInfo;
    
        @ApiModelProperty(value = "用户所属组织")
        @ManyToOne
        @JoinColumn(name = "org_id", updatable = false, insertable = false)
        private Organization org;
    
        @ApiModelProperty(value = "用户角色")
        @OneToMany
        @JoinColumn(name = "user_id", referencedColumnName = "id", insertable = false, updatable = false)
        @NotFound(action = NotFoundAction.IGNORE)
        private Set<Role> roles;
    
        @ApiModelProperty(value = "用户工作")
        @ManyToMany
        @JoinTable(
                name = "t_user_job",
                joinColumns = @JoinColumn(name = "user_id", referencedColumnName = "id"),
                inverseJoinColumns = @JoinColumn(name = "job_id", referencedColumnName = "id")
        )
        @NotFound(action = NotFoundAction.IGNORE)
        private Set<Job> jobs;
    

    private Set<Role> roles;private Set<Job> jobs;不能用同时使用List集合代替,会报错org.hibernate.loader.MultipleBagFetchException: cannot simultaneously fetch multiple bags: [com.yizhu.entity.User.jobs, com.yizhu.entity.User.roles]

    动态查询

    package com.yizhu.repository;
    
    import com.yizhu.dto.UserQueryDto;
    import com.yizhu.entity.Organization;
    import com.yizhu.entity.User;
    import org.springframework.data.jpa.domain.Specification;
    
    import javax.persistence.criteria.Join;
    import javax.persistence.criteria.JoinType;
    import javax.persistence.criteria.Predicate;
    import java.util.ArrayList;
    import java.util.List;
    import java.util.Optional;
    
    public class UserSpecs {
    
        public static Specification<User> listQuerySpec(UserQueryDto userQueryDto){
            return (root, query, builder) -> {
                List<Predicate> predicates = new ArrayList<>();
    
                Optional.ofNullable(userQueryDto.getId()).ifPresent(i -> predicates.add(builder.equal(root.get("id"), i)));
                Optional.ofNullable(userQueryDto.getName()).ifPresent(n -> predicates.add(builder.equal(root.get("name"), n)));
                Optional.ofNullable(userQueryDto.getAge()).ifPresent(a -> predicates.add(builder.equal(root.get("age"), a)));
                Optional.ofNullable(userQueryDto.getOrgId()).ifPresent(oi -> predicates.add(builder.equal(root.get("orgId"), oi)));
                Optional.ofNullable(userQueryDto.getOrgName()).ifPresent(on -> {
                    Join<User, Organization> userJoin = root.join(root.getModel().getSingularAttribute("org", Organization.class), JoinType.LEFT);
                    predicates.add(builder.equal(userJoin.get("orgName"), on));
                });
    
                return builder.and(predicates.toArray(new Predicate[predicates.size()]));
            };
        }
    }
    
    package com.yizhu.service;
    
    import com.yizhu.dto.UserQueryDto;
    import com.yizhu.entity.User;
    import com.yizhu.repository.UserRepository;
    import com.yizhu.repository.UserSpecs;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.stereotype.Service;
    
    import java.util.List;
    
    @Service
    public class UserService {
    
        @Autowired
        private UserRepository userRepository;
    
        public List<User> findUsersDynamic(UserQueryDto userQueryDto){
            return userRepository.findAll(UserSpecs.listQuerySpec(userQueryDto));
        }
    }
    

    审计功能使用

    在启动类添加@EnableJpaAuditing注解表示开启jpa审计功能

    package com.yizhu;
    
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    import org.springframework.data.jpa.repository.config.EnableJpaAuditing;
    
    @EnableJpaAuditing
    @SpringBootApplication
    public class DemoApplication {
    
        public static void main(String[] args) {
            SpringApplication.run(DemoApplication.class, args);
        }
    }
    

    在需要使用审计功能的实体类添加@EntityListeners(AuditingEntityListener.class)注解

    package com.yizhu.entity;
    
    import lombok.Builder;
    import lombok.Data;
    import org.springframework.data.jpa.domain.support.AuditingEntityListener;
    
    import javax.persistence.*;
    import java.io.Serializable;
    import java.util.Date;
    
    @Entity
    @Table(name = "t_role")
    @Data
    @Builder
    @EntityListeners(AuditingEntityListener.class)
    public class Role implements Serializable {
        private static final long serialVersionUID=1L;
    
        @ApiModelProperty(hidden = true)
        @Id
        @GeneratedValue(strategy = GenerationType.AUTO)
        private Long id;
    
        private String roleName;
    
        @CreatedDate
        private Date createTime;
        
        @CreatedBy
        private Long createId;
        
        @LastModifiedDate
        private Date updateTime;
        
        @LastModifiedBy
        private Long updateId;
    }
    

    实现AuditorAware接口,告诉容器当前登录人id

    package com.yizhu.configuration;
    
    import org.springframework.data.domain.AuditorAware;
    import org.springframework.web.context.request.RequestContextHolder;
    import org.springframework.web.context.request.ServletRequestAttributes;
    
    import java.util.Optional;
    
    public class UserAuditorAwareImpl implements AuditorAware<Long> {
        @Override
        public Optional<Long> getCurrentAuditor() {
            // 从session中获取登录人id
            ServletRequestAttributes servletRequestAttributes = (ServletRequestAttributes) RequestContextHolder.getRequestAttributes();
            Long userId = (Long)servletRequestAttributes.getRequest().getSession().getAttribute("userId");
            return Optional.of(userId);
        }
    }
    

    ok,然后jpa就会根据IDVersion判断当前操作是更新还是新增数据,新增时会注入当前登录人id到标有@CreateBy注解的字段上,当前时间注入到标有@CreateTime注解字段上;更新时则注入到@LastModifiedBy@LastModifiedDate对应的字段上。想详细了解的可查看org.springframework.data.jpa.domain.support.AuditingEntityListener源码。

    常见的坑

    • N+1问题,当使用@ManyToMany@ManyToOne@OneToMany@OneToOne关联
      关系的时候,FetchType怎么配置LAZY或者EAGER。SQL真正执行的时
      候是由一条主表查询和N条子表查询组成的。这种查询效率一般比较
      低下,比如子对象有N个就会执行N+1条SQL。使用JPA 2.1推出来的@EntityGraph、@NamedEntityGraph可以解决该问题。如下。
    @ApiModel
    @Entity
    @Table(name = "t_user")
    @NamedEntityGraph(name = "User.findUsers", attributeNodes = {@NamedAttributeNode("jobs"), @NamedAttributeNode("roles")})
    @Data
    @Builder
    @NoArgsConstructor
    @AllArgsConstructor
    public class User implements Serializable {
    
        private static final long serialVersionUID = 1L;
    
        @ApiModelProperty(hidden = true)
        @Id
        @GeneratedValue(strategy = GenerationType.IDENTITY)
        private Long id;
        
        // 省略其他属性
    }
    
    package com.yizhu.repository;
    
    import com.yizhu.entity.User;
    import org.springframework.data.jpa.repository.EntityGraph;
    import org.springframework.data.jpa.repository.JpaRepository;
    import org.springframework.data.jpa.repository.JpaSpecificationExecutor;
    import org.springframework.data.jpa.repository.Query;
    import org.springframework.data.repository.query.Param;
    import java.util.List;
    
    public interface UserRepository extends JpaRepository<User, Long>, JpaSpecificationExecutor<User> {
    
        /**
         * 根据id查询用户信息
         * @param id
         * @return
         */
        @EntityGraph(value = "User.findUsers", type = EntityGraph.EntityGraphType.FETCH)
        User findAllById(Long id);
    
        /**
         * 根据name查询用户信息
         * @param name
         * @return
         */
        @EntityGraph(value = "User.findUsers", type = EntityGraph.EntityGraphType.FETCH)
        @Query(value = "select * from t_user where user_name = :name", nativeQuery = true)
        List<User> findAllByUserName(@Param("name") String name);
    }
    
    • 所有的注解要么全配置在字段上,要么全配置在get方法上,不能混用,混用就会启动不起来,但是语法配置没有问题。
    • 所有的关联都是支持单向关联和双向关联的,视具体业务场景而定。JSON序列化的时候使用双向注解会产生死循环,需要人为手动转化一次,或者使用@JsonIgnore。
    • 在所有的关联查询中,表一般是不需要建立外键索引的。@mappedBy的使用需要注意。
    • 级联删除比较危险,建议考虑清楚,或者完全掌握。
    • 不同的关联关系的配置,@JoinClumn里面的name、referencedColumnName代表的意思是不一样的,很容易弄混,可以根据打印出来的SQL做调整。
    • 当配置这些关联关系的时候建议大家直接在表上面,把外键建好,然后通过后面我们介绍的开发工具直接生成,这样可以减少自己调试的时间。

    JPA常用注解

    摘自《Spring Data JPA从入门到精通》

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