Hibernate @SortComparator and @SortNatural Example for SortedSet Mapping
February 07, 2016
@Sort annotation. @SortComparator specifies comparator class which implements Comparator interface and @SortNatural uses sorting with Comparable interface implemented by entity. @SortComparator and @SortNatural performs in-memory sorting for Set and Map. Their functions are different from @OrderBy because it is applied during SQL SELECT. Here we will provide complete example for @SortComparator and @SortNatural annotations.
Software Used
We are using following software and tools in our demo.1. Java 8
2. Hibernate 4.3
3. Gradle
4. Eclipse
5. MySQL
Table Data used in Demo
Find the data for book table.
Gradle File
Find the gradle file to resolve the JAR dependencies.build.gradle
apply plugin: 'java'
apply plugin: 'eclipse'
archivesBaseName = 'hibernate'
version = '1'
repositories {
mavenCentral()
}
dependencies {
compile 'org.hibernate:hibernate-core:4.3.11.Final'
compile 'mysql:mysql-connector-java:5.1.31'
}
SortedSet Mapping with @SortComparator
@SortComparator is used to specify java Comparator to sort the Set and Map. Find the code snippet for how to use.
@OneToMany(cascade=CascadeType.ALL, fetch=FetchType.EAGER)
@JoinColumn(name="std_id")
@SortComparator(BookNameComparator.class)
private SortedSet<Book> books;
public int getStdId() {
return stdId;
}
Book.java
package com.concretepage;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Table;
@Entity
@Table(name ="book")
public class Book {
@Id
@Column(name ="book_id")
private int bookId;
@Column(name = "book_name")
private String bookName;
@Column(name = "writer")
private String writer;
public int getBookId() {
return bookId;
}
public void setBookId(int bookId) {
this.bookId = bookId;
}
public String getBookName() {
return bookName;
}
public void setBookName(String bookName) {
this.bookName = bookName;
}
public String getWriter() {
return writer;
}
public void setWriter(String writer) {
this.writer = writer;
}
}
package com.concretepage;
import java.util.Comparator;
public class BookNameComparator implements Comparator<Book> {
@Override
public int compare(Book b1, Book b2) {
return b1.getBookName().compareTo(b2.getBookName());
}
}
package com.concretepage;
import java.util.SortedSet;
import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.OneToMany;
import javax.persistence.Table;
import org.hibernate.annotations.SortComparator;
@Entity
@Table(name = "student")
public class Student {
@Id
@Column(name = "std_id")
private int stdId;
@Column(name = "std_name")
private String stdName;
@OneToMany(cascade=CascadeType.ALL, fetch=FetchType.EAGER)
@JoinColumn(name="std_id")
@SortComparator(BookNameComparator.class)
private SortedSet<Book> books;
public int getStdId() {
return stdId;
}
public void setStdId(int stdId) {
this.stdId = stdId;
}
public String getStdName() {
return stdName;
}
public void setStdName(String stdName) {
this.stdName = stdName;
}
public SortedSet<Book> getBooks() {
return books;
}
public void setBooks(SortedSet<Book> books) {
this.books = books;
}
}
<hibernate-configuration>
<session-factory>
<property name="connection.driver_class">com.mysql.jdbc.Driver</property>
<property name="hibernate.connection.url">
jdbc:mysql://localhost:3306/concretepage</property>
<property name="hibernate.connection.username">root</property>
<property name="hibernate.connection.password"></property>
<property name="hibernate.connection.pool_size">10</property>
<property name="show_sql">true</property>
<property name="dialect">org.hibernate.dialect.MySQLDialect</property>
<property name="hibernate.hbm2ddl.auto">update</property>
<mapping class="com.concretepage.Book"/>
<mapping class="com.concretepage.Student"/>
</session-factory>
</hibernate-configuration>
package com.concretepage;
import org.hibernate.SessionFactory;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
import org.hibernate.cfg.Configuration;
public class HibernateUtil {
private static SessionFactory sessionFactory ;
static {
Configuration configuration = new Configuration().configure();
StandardServiceRegistryBuilder builder = new StandardServiceRegistryBuilder().
applySettings(configuration.getProperties());
sessionFactory = configuration.buildSessionFactory(builder.build());
}
public static SessionFactory getSessionFactory() {
return sessionFactory;
}
public static void closeSessionFactory() {
sessionFactory.close();
}
}
package com.concretepage;
import org.hibernate.Session;
public class HibernateDemo {
public static void main(String[] args) {
Session session = HibernateUtil.getSessionFactory().openSession();
Student student = (Student) session.get(Student.class, new Integer(1));
for (Book book: student.getBooks()) {
System.out.println(book.getBookName());
}
session.close();
HibernateUtil.closeSessionFactory();
}
}
Hibernate: select student0_.std_id as std_id1_1_0_, student0_.std_name as std_name2_1_0_, books1_.std_id as std_id4_1_1_, books1_.book_id as book_id1_0_1_, books1_.book_id as book_id1_0_2_, books1_.book_name as book_nam2_0_2_, books1_.writer as writer3_0_2_ from student student0_ left outer join book books1_ on student0_.std_id=books1_.std_id where student0_.std_id=? Mahabharat Nirmla Ramayan
SortedSet Mapping with @SortNatural
@SortNatural annotation uses Comparable to sort the data. The entity implements Comparable interface. For the code snippet.
@OneToMany(cascade=CascadeType.ALL, fetch=FetchType.EAGER) @JoinColumn(name="std_id") @SortNatural private SortedSetbooks; public int getStdId() { return stdId; }
Book.java
package com.concretepage;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Table;
@Entity
@Table(name ="book")
public class Book implements Comparable<Book> {
@Id
@Column(name ="book_id")
private int bookId;
@Column(name = "book_name")
private String bookName;
@Column(name = "writer")
private String writer;
@Override
public int compareTo(Book o) {
return writer.compareTo(o.getWriter());
}
//setter getter
}
package com.concretepage;
import java.util.SortedSet;
import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.OneToMany;
import javax.persistence.Table;
import org.hibernate.annotations.SortNatural;
@Entity
@Table(name = "student")
public class Student {
@Id
@Column(name = "std_id")
private int stdId;
@Column(name = "std_name")
private String stdName;
@OneToMany(cascade=CascadeType.ALL, fetch=FetchType.EAGER)
@JoinColumn(name="std_id")
@SortNatural
private SortedSet<Book> books;
//setter getter
}
HibernateDemo class by following.
for (Book book: student.getBooks()) {
System.out.println(book.getWriter());
}
Hibernate: select student0_.std_id as std_id1_1_0_, student0_.std_name as std_name2_1_0_, books1_.std_id as std_id4_1_1_, books1_.book_id as book_id1_0_1_, books1_.book_id as book_id1_0_2_, books1_.book_name as book_nam2_0_2_, books1_.writer as writer3_0_2_ from student student0_ left outer join book books1_ on student0_.std_id=books1_.std_id where student0_.std_id=? Premchand Valmiki Vyas
