在休眠中保存值类型集合

本文介绍了在休眠中保存值类型集合的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

如何在休眠状态下使用注释保存值类型的集合-字符串 List< String> 的 List 或例如:

How can I save collection of value type in hibernate with annotations - List of String List<String> or for example:

@Entity public class Student { @Id @GeneratedValue(strategy = GenerationType.IDENTITY) @Column(name = "id") private int id; private Set<History> history; }

这是值类型:

public class History { private String someAttribute; @Override public int hashCode() { final int prime = 31; int result = 1; result = prime * result + ((entry == null) ? 0 : entry.hashCode()); result = prime * result + ((entryDate == null) ? 0 : entryDate.hashCode()); return result; } @Override public boolean equals(Object obj) { if (this == obj) return true; if (obj == null) return false; if (getClass() != obj.getClass()) return false; History other = (History) obj; if (entry == null) { if (other.entry != null) return false; } else if (!entry.equals(other.entry)) return false; if (entryDate == null) { if (other.entryDate != null) return false; } else if (!entryDate.equals(other.entryDate)) return false; return true; } }

有人可以举一些带有休眠注释的示例吗?

Can anyone give some example with hibernate annotations?

推荐答案

对于具有集合值类型的实体，我们需要创建一个单独的表来保存此集合，因为该实体的单行将为此具有多个值收藏.在集合值属性上使用@ElementCollection和@CollectionTable批注.

For an entity to have collection value type, we need to create a separate table to hold this collection as single row of the entity will have multiple values of for this collection. Use @ElementCollection and @CollectionTable annotations on the collection value attribute.

@ElementCollection @CollectionTable(name = "STUDENT_HISTORY", joinColumns = {@JoinColumn(name = STUDENT_ID) }) @Column(name="HISTORY") private Set<History> history;

该表将在HISTORY列中保存集合值，并将STUDENT_ID列用作连接列，这将是学生ID的外键.

The table will hold the collection values in the column HISTORY and uses STUDENT_ID column as the join column which will be the foreign key to the ID of student.

以下是使用本地Hibernate的完整示例(我的意思是没有JPA):

Below is a complete example using native Hibernate (I mean without the JPA):

Student.java

package domain.app.data; import java.util.HashSet; import java.util.Set; import javax.persistence.CollectionTable; import javax.persistence.Column; import javax.persistence.ElementCollection; import javax.persistence.Entity; import javax.persistence.GeneratedValue; import javax.persistence.GenerationType; import javax.persistence.Id; import javax.persistence.JoinColumn; @Entity public class Student { @Id @GeneratedValue(strategy=GenerationType.IDENTITY) private Long id; @ElementCollection @CollectionTable(name="STUDENT_HISTORY", joinColumns={@JoinColumn(name="STUDENT_ID", referencedColumnName="ID")}) @Column(name="HISTORY") private Set<History> history = new HashSet<>(); public Long getId() { return id; } public void setId(Long id) { this.id = id; } public Set<History> getHistory() { return history; } public void setHistory(Set<History> history) { this.history = history; } @Override public String toString() { return "Student [id=" + id + ", history=" + history + "]"; } }

History.java

package domain.app.data; import javax.persistence.Column; import javax.persistence.Embeddable; @Embeddable public class History { @Column(name="HISTORY") private String someAttribute; public String getSomeAttribute() { return someAttribute; } public void setSomeAttribute(String someAttribute) { this.someAttribute = someAttribute; } @Override public int hashCode() { final int prime = 31; int result = 1; result = prime * result + ((someAttribute == null) ? 0 : someAttribute.hashCode()); return result; } @Override public boolean equals(Object obj) { if (this == obj) return true; if (obj == null) return false; if (getClass() != obj.getClass()) return false; History other = (History) obj; if (someAttribute == null) { if (other.someAttribute != null) return false; } else if (!someAttribute.equals(other.someAttribute)) return false; return true; } }

HibernateUtil.java

package domain.app.data.util; import org.hibernate.SessionFactory; import org.hibernate.boot.registry.StandardServiceRegistry; import org.hibernate.boot.registry.StandardServiceRegistryBuilder; import org.hibernate.cfg.Configuration; import domain.app.data.Student; public class HibernateUtil { private static final SessionFactory sessionFactory = buildSessionFactory(); private static SessionFactory buildSessionFactory() { StandardServiceRegistry serviceRegistry = new StandardServiceRegistryBuilder().build(); Configuration configuration = new Configuration(); configuration.addAnnotatedClass(Student.class); return configuration.buildSessionFactory(serviceRegistry); } public static SessionFactory getSession() { return sessionFactory; } }

Application.java

package domain.app; import org.hibernate.Session; import domain.app.data.History; import domain.app.data.Student; import domain.app.data.util.HibernateUtil; public class Application { public static void main(String[] args) { Session session = HibernateUtil.getSession().openSession(); session.getTransaction().begin(); Student student = new Student(); History history1 = new History(); history1.setSomeAttribute("Volunteer since 2016"); History history2 = new History(); history2.setSomeAttribute("Football team member"); student.getHistory().add(history1); student.getHistory().add(history2); session.save(student); session.getTransaction()mit(); session.close(); } }

hibernate.properties

hibernate.connection.username=admin hibernate.connection.password=password hibernate.connection.url=jdbc:h2:~/h2db/test hibernate.connection.driver_class=org.h2.Driver hibernate.dialect=org.hibernate.dialect.H2Dialect hibernate.show_sql=true hibernate.hbm2ddl.auto=create

logback.xml

<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE xml> <configuration debug="false" scan="true" scanPeriod="30 minutes"> <appender name="Console-Appender" class="ch.qos.logback.core.ConsoleAppender"> <encoder> <pattern>%gray(%d{yyyy-MM-dd HH:mm:ss.SSS}) %highlight(%5p) %gray(---) %magenta([%15.15t]) %cyan(%-40.40c{1}) %black(:) %m%n%xEx</pattern> </encoder> </appender> <root level="trace"> <appender-ref ref="Console-Appender" /> </root> </configuration>

pom.xml

<project xmlns="maven.apache/POM/4.0.0" xmlns:xsi="www.w3/2001/XMLSchema-instance" xsi:schemaLocation="maven.apache/POM/4.0.0 maven.apache/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>stackoverflow</groupId> <artifactId>SO-41248001</artifactId> <version>0.0.1-SNAPSHOT</version> <build> <plugins> <plugin> <artifactId>maven-compiler-plugin</artifactId> <version>3.5.1</version> <configuration> <source>1.8</source> <target>1.8</target> </configuration> </plugin> </plugins> </build> <dependencies> <dependency> <groupId>org.hibernate</groupId> <artifactId>hibernate-core</artifactId> <version>5.2.5.Final</version> </dependency> <dependency> <groupId>com.h2database</groupId> <artifactId>h2</artifactId> <version>1.4.192</version> </dependency> <dependency> <groupId>org.slf4j</groupId> <artifactId>slf4j-api</artifactId> <version>1.7.21</version> </dependency> <dependency> <groupId>ch.qos.logback</groupId> <artifactId>logback-classic</artifactId> <version>1.1.7</version> </dependency> </dependencies> </project>

项目结构:

数据库结果: