java code for Collection Mapping: Many-To-Many map based on HashMap

public class Benefit {
private int id;
private int cost;

public Benefit() {
}

public Benefit(int c) {
cost = c;
}

public void setId(int i) {
id = i;
}

public int getId() {
return id;
}

public void setCost(int i) {
cost = i;
}

public int getCost() {
return cost;
}
}

/////////////////////////////////////////////////////////////////////////


PUBLIC "-//Hibernate/Hibernate Mapping DTD//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd">



















/////////////////////////////////////////////////////////////////////////


import java.util.*;

public class Employee {
private int id;
private String name;
private Map benefits;

public Employee() {
}

public void setId(int i) {
id = i;
}

public int getId() {
return id;
}

public void setName(String s) {
name = s;
}

public String getName() {
return name;
}

public void setBenefits(Map m) {
benefits = m;
}

public Map getBenefits() {
return benefits;
}
}
/////////////////////////////////////////////////////////////////////////



"-//Hibernate/Hibernate Configuration DTD//EN"
"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">



org.hsqldb.jdbcDriver
jdbc:hsqldb:data/tutorial
sa



1


org.hibernate.dialect.HSQLDialect


true






/////////////////////////////////////////////////////////////////////////

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.Statement;

import java.sql.ResultSet;
import java.sql.ResultSetMetaData;

import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;

public class HibernateUtil {

public static final SessionFactory sessionFactory;

static {
try {
// Create the SessionFactory from hibernate.cfg.xml
sessionFactory = new Configuration().configure().buildSessionFactory();
} catch (Throwable ex) {
// Make sure you log the exception, as it might be swallowed
System.err.println("Initial SessionFactory creation failed." + ex);
throw new ExceptionInInitializerError(ex);
}
}

public static final ThreadLocal session = new ThreadLocal();

public static Session currentSession() throws HibernateException {
Session s = (Session) session.get();
// Open a new Session, if this thread has none yet
if (s == null) {
s = sessionFactory.openSession();
// Store it in the ThreadLocal variable
session.set(s);
}
return s;
}

public static void closeSession() throws HibernateException {
Session s = (Session) session.get();
if (s != null)
s.close();
session.set(null);
}

static Connection conn;
static Statement st;
public static void setup(String sql) {
try {
// Step 1: Load the JDBC driver.
Class.forName("org.hsqldb.jdbcDriver");
System.out.println("Driver Loaded.");
// Step 2: Establish the connection to the database.
String url = "jdbc:hsqldb:data/tutorial";

conn = DriverManager.getConnection(url, "sa", "");
System.out.println("Got Connection.");

st = conn.createStatement();
st.executeUpdate(sql);
} catch (Exception e) {
System.err.println("Got an exception! ");
e.printStackTrace();
System.exit(0);
}
}
public static void checkData(String sql) {
try {
HibernateUtil.outputResultSet(st
.executeQuery(sql));
// conn.close();
} catch (Exception e) {
e.printStackTrace();
}
}

public static void outputResultSet(ResultSet rs) throws Exception{
ResultSetMetaData metadata = rs.getMetaData();

int numcols = metadata.getColumnCount();
String[] labels = new String[numcols];
int[] colwidths = new int[numcols];
int[] colpos = new int[numcols];
int linewidth;

for (int i = 0; i < numcols; i++) {
labels[i] = metadata.getColumnLabel(i + 1); // get its label
System.out.print(labels[i]+" ");
}
System.out.println("------------------------");

while (rs.next()) {
for (int i = 0; i < numcols; i++) {
Object value = rs.getObject(i + 1);
if(value == null){
System.out.print(" ");
}else{
System.out.print(value.toString().trim()+" ");
}

}
System.out.println(" ");
}
}
}


/////////////////////////////////////////////////////////////////////////

import java.io.Serializable;
import java.util.*;

import org.hibernate.*;
import org.hibernate.cfg.*;
import org.hibernate.criterion.*;
import org.hibernate.event.*;
import org.hibernate.event.def.*;

public class Main {
public static void main(String[] args) throws Exception {
HibernateUtil.setup("create table employee (id int,name varchar);");
HibernateUtil.setup("create table benefit (id int,cost int);");
HibernateUtil.setup("create table employee_benefit (parent_id int,benefit_name varchar,benefit_id int);");


Session session = HibernateUtil.currentSession();
Employee sp = new Employee();
Employee sp3 = new Employee();

sp.setName("Joe");
HashMap p = new HashMap();
p.put("health", new Benefit(200));
p.put("dental", new Benefit(300));
sp.setBenefits(p);

sp3.setName("Jim");
sp3.setBenefits(p);

session.save(sp);
session.save(sp3);
session.flush();

HibernateUtil.closeSession();
session = HibernateUtil.currentSession();

Employee sp2 = (Employee)session.load(Employee.class, new Integer(sp.getId()));

Map p2 = sp2.getBenefits();
System.out.println(((Benefit)p2.get("health")).getCost());
System.out.println(((Benefit)p2.get("dental")).getCost());


session.flush();
session.close();
HibernateUtil.checkData("select * from employee");
HibernateUtil.checkData("select * from benefit");
HibernateUtil.checkData("select * from employee_benefit");
}
}