Hibernate 5无外键表关联

╰+攻爆jí腚メ 2022-05-24 05:51 214阅读 0赞

## 前期准备 ##

准备搭建一个Springboot+JPA(Hibernate)作为例子

### pom配置 ###

<parent>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-parent</artifactId>
            <version>1.5.10.RELEASE</version>
            <relativePath/> 
        </parent>
    
        <properties>
            <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
            <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
            <java.version>1.8</java.version>
        </properties>
    
        <dependencies>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-data-jpa</artifactId>
            </dependency>
    
            <dependency>
                <groupId>mysql</groupId>
                <artifactId>mysql-connector-java</artifactId>
                <scope>runtime</scope>
            </dependency>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-test</artifactId>
                <scope>test</scope>
            </dependency>
        </dependencies>
    
        <build>
            <plugins>
                <plugin>
                    <groupId>org.springframework.boot</groupId>
                    <artifactId>spring-boot-maven-plugin</artifactId>
                </plugin>
            </plugins>
        </build>

### application.properties配置 ###

spring.datasource.url=jdbc:mysql://localhost:3306/demo
    spring.datasource.username=root
    spring.datasource.password=yourpwd
    
    spring.jpa.properties.hibernate.hbm2ddl.auto=update
    spring.jpa.properties.hibernate.show_sql=true
    spring.jpa.properties.hibernate.format_sql=true
    spring.jpa.properties.hibernate.dialect=org.hibernate.dialect.MySQLDialect

## 一对一 ##

用户User

@Entity
    public class User implements Serializable { 
    
        @Id
        @GeneratedValue
        private Long userId;
    
        private String userName;
    
        //省略Get/Set方法
    }

操作日志OperationLog

@Entity
    public class OperationLog implements Serializable { 
    
        @Id
        @GeneratedValue
        private Long id;
    
        private String content;
    
        @OneToOne
        @JoinColumn(name = "op_id",referencedColumnName = "userId",foreignKey = @ForeignKey(value = ConstraintMode.NO_CONSTRAINT))
        @NotFound(action = NotFoundAction.IGNORE)
        private User user;
    
        //省略Get/Set方法
    }

Hibernate的建表语句

CREATE TABLE `operation_log` ( `id` bigint(20) NOT NULL AUTO_INCREMENT, `content` varchar(255) DEFAULT NULL, `op_id` bigint(20) DEFAULT NULL, PRIMARY KEY (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8;
    
    CREATE TABLE `user` ( `user_id` bigint(20) NOT NULL AUTO_INCREMENT, `user_name` varchar(255) DEFAULT NULL, PRIMARY KEY (`user_id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8;

## 一对多 ##

书籍Book

@Entity
    public class Book implements Serializable { 
        /** * 逻辑主键，自增长 */
        @Id
        @GeneratedValue
        private Long bookId;
        /** * 书籍名称 */
        private String name;
    
        //省略Get/Set方法
    }

作者Author

@Entity
    public class Author implements Serializable { 
        /** * 逻辑主键，自增长 */
        @Id
        @GeneratedValue
        private Long id;
        /** * 作者名称 */
        private String name;
        /** * 作者名下的书籍 */
        @OneToMany(fetch=FetchType.EAGER)
        @JoinTable(name = "author_book",joinColumns = @JoinColumn(name="author_id"),inverseJoinColumns = @JoinColumn(name = "book_id"),foreignKey = @ForeignKey(ConstraintMode.NO_CONSTRAINT))
        @NotFound(action=NotFoundAction.IGNORE)
        private List<Book> books;
    
        //省略Get/Set方法
    }

Hibernate的建表语句

CREATE TABLE `author` ( `id` bigint(20) NOT NULL AUTO_INCREMENT, `name` varchar(255) DEFAULT NULL, PRIMARY KEY (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8;
    
    CREATE TABLE `author_book` ( `author_id` bigint(20) NOT NULL, `book_id` bigint(20) NOT NULL, UNIQUE KEY `UK_bfff0qy5yokmeel0q0e10msv7` (`book_id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8;
    
    CREATE TABLE `book` ( `book_id` bigint(20) NOT NULL AUTO_INCREMENT, `name` varchar(255) DEFAULT NULL, PRIMARY KEY (`book_id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8;

## 总结 ##

1、无外键关联的关键是`@ForeignKey(value = ConstraintMode.NO_CONSTRAINT)`  
2、`@NotFound(action=NotFoundAction.IGNORE)`是用来防止无关联的数据的时候抛出异常