Hibernate for Oracle DBAs

Warning: any smart developer may feel sick when reading this ;)

I am not a developer, but I like to discuss with developers: share my side of the IT (the database that we want rock stable and durable) and listen to their side (the application that they want easy to maintain and evolve). And, as I like to understand what I’m talking about, I often need to test some snippets.

Many DBAs complain about Hibernate when they come upon the queries generated by a wrong mapping. They think it was designed to be bad (who would do that?). And they are convinced that JDBC and SQL are sufficient to build applications. Actually, many DBAs I have seen are persuaded that they understand everything about coding because they have written some ugly PERL scripts to automate their job. And that anything going beyond has the only goal to break the database.

I didn’t go this way. As I like to understand before building my opinion, I have read “Hibernate In Action” and tested some object to relational mapping. I’m talking about Hibernate 3 times here. I’ve found those tests in a folder from 2008. I re-used this today for a short test and that’s the reason for this post.

Here I am showing how I’m doing those small tests with Hibernate. I’m a DBA and I cannot have an Eclipse environment taking all my screens, hiding those database top activity charts. And all my RAM is already eaten by SQL Developer and Chrome Grid Control windows, no room for Eclipse. And anyway, those mouse-focused IDEs are not friends with my carpal tunnel. I like the keyboard and tty.

So, for simple tests, I need simple things which can be reduced to a command line and 1 file that I can open with vi. The goal of this post is to show how it is easy to test some Hibernate thing in this case. Of course, any real developer will vomit when looking at this… don’t forget this is about short tests only.

Libraries

So, no Maven for me. I download the whole Hibernate .zip and build a CLASSPATH with everything I found in the required lib folder.

wget https://netix.dl.sourceforge.net/project/hibernate/hibernate-orm/5.4.3.Final/hibernate-release-5.4.3.Final.zip
unzip hibernate-release-5.4.3.Final.zip
for i in hibernate-release-5.4.3.Final/lib/required/*.jar 
do
 CLASSPATH="${CLASSPATH}:$i"
done
export CLASSPATH=.:$ORACLE_HOME/jdbc/lib/ojdbc8.jar:$CLASSPATH

You can see that I’ve added the Oracle JDBC as I’ll connect to an Oracle database that I have locally (I use Oracle Cloud DBaaS here).

Compile

No Ant here. I compile the .java files I have in my folder (I don’t use packages and subfolders for simple tests). Note that, from a past admiration for makefiles, I add enough intelligence (like “test -nt”) to compile only when the code is newer than the source.

for i in *.java
do
 if [ $i -nt $(basename $i .java).class ]
 then
  $ORACLE_HOME/jdk/bin/javac $i
 fi
done

ORM Mapping

My goal was to quickly test the following mapping from @vlad_mihalcea:

The best way to map a Composite Primary Key with JPA and Hibernate - Vlad Mihalcea

So what do I have in those .java files? Testing Hibernate needs having many classes. And in Java, each class goes to its own file. But did I say that I want to open only 1 file? I use inner classes.

import java.io.*;
import java.sql.*;
import java.util.*;
import oracle.jdbc.*;
import org.hibernate.*;
import org.hibernate.cfg.*;
import javax.persistence.*;
public class Franck {
@Entity(name = "Company")
@Table(name = "company")
public class Company {
    @Id
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    private Long id;
    private String name;
    public Long getId() {
        return id;
    }
    public void setId(Long id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (!(o instanceof Company)) return false;
        Company company = (Company) o;
        return Objects.equals(getName(), company.getName());
    }
    @Override
    public int hashCode() {
        return Objects.hash(getName());
    }
}
@Embeddable
public class EmployeeId implements Serializable {
    @ManyToOne
    @JoinColumn(name = "company_id")
    private Company company;
    @Column(name = "employee_number")
    private Long employeeNumber;
    public EmployeeId() {
    }
    public EmployeeId(Company company, Long employeeId) {
        this.company = company;
        this.employeeNumber = employeeId;
    }
    public Company getCompany() {
        return company;
    }
    public Long getEmployeeNumber() {
        return employeeNumber;
    }
    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (!(o instanceof EmployeeId)) return false;
        EmployeeId that = (EmployeeId) o;
        return Objects.equals(getCompany(), that.getCompany()) &&
                Objects.equals(getEmployeeNumber(), that.getEmployeeNumber());
    }
    @Override
    public int hashCode() {
        return Objects.hash(getCompany(), getEmployeeNumber());
    }
}
@Entity(name = "Employee")
@Table(name = "employee")
public class Employee {
    @EmbeddedId
    private EmployeeId id;
    private String name;
    public EmployeeId getId() {
        return id;
    }
    public void setId(EmployeeId id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
}
public static void main(String[] args) throws SQLException {
 SessionFactory sf=new Configuration()
  .addAnnotatedClass(Employee.class)
  .addAnnotatedClass(Company.class)
  .setProperty("hibernate.connection.url","jdbc:oracle:thin:@//localhost/PDB1")
  .setProperty("hibernate.connection.driver_class","oracle.jdbc.driver.OracleDriver")
  .setProperty("hibernate.connection.username","demo")
  .setProperty("hibernate.connection.password","demo")
  .setProperty("hibernate.format_sql","true")
  .setProperty("hibernate.show_sql","true")
  .setProperty("hibernate.hbm2ddl.auto","create")
  .buildSessionFactory();
}
}

The main class name (here Franck) matches the file name (Franck.java) and all my entities are inner classes here. After compilation here are my files:

-rwxr--r--. 1 oracle 4931 Jun  5 20:18 Franck.java
-rw-r--r--. 1 oracle 1304 Jun  5 20:19 Franck$Company.class
-rw-r--r--. 1 oracle 1398 Jun  5 20:19 Franck$EmployeeId.class
-rw-r--r--. 1 oracle  922 Jun  5 20:19 Franck$Employee.class
-rw-r--r--. 1 oracle 1557 Jun  5 20:19 Franck.class

Execution

$ORACLE_HOME/jdk/bin/java Franck

This generates the following:

That’s all I need to verify what my annotations generate with the Oracle 12c Dialect. Ugly on-file code, but sufficient for this goal.

Java as a Shell

Ok, now that I think that any real developer has stopped reading, I can confess that I add the following on the top of my .java file:

/*TAG-FOR-SHELL 2>/dev/null
CLASSPATH=.
# Oracle JDBC
CLASSPATH=${CLASSPATH}:$ORACLE_HOME/jdbc/lib/ojdbc8.jar
# Download Hibernate
[ -f /var/tmp/hibernate.zip ] || wget -O /var/tmp/hibernate.zip https://netix.dl.sourceforge.net/project/hibernate/hibernate-orm/5.4.3.Final/hibernate-release-5.4.3.Final.zip
# Unzip Hibernate
[ -d /var/tmp/hibernate*?/lib/required ] || unzip -d /var/tmp /var/tmp/hibernate.zip
# add libs to CLASSPATH
for l in /var/tmp/hibernate*?/lib/required/*.jar ; do CLASSPATH="${CLASSPATH}:$l" ; done ; export CLASSPATH
# compile all Java
for s in $(find -name "*.java"); do
s="$(basename $s .java)"
[ $s.java -nt $s.class ] && {
        echo "Compiling $s..." >&2
        $ORACLE_HOME/jdk/bin/javac $s.java || exit 1
}
done
# execute
$ORACLE_HOME/jdk/bin/java $(basename $0 .java)
exit
*/

And then I “chmod u+x” this .java file and run it as a shell. The shell part is included in Java comment so that this file can be compiled as Java source code. And it gets the libraries if not there already, builds CLASSPATH, compile what’s new in the directory, and run it as a Java program. all that with a simple:

./Franck.java

Any comments welcome on Twitter: @FranckPachot