Java Developers' Oracle Database Guide

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Oracle Database Overview
Installation and Setup
Oracle Database Architecture
SQL Fundamentals
Advanced Oracle Features
Java Database Connectivity
Connection Management
ORM Frameworks
Performance Optimization
Security Best Practices
Monitoring and Maintenance

Oracle Database Overview

Oracle Database is a multi-model database management system produced by Oracle Corporation. It’s one of the most widely used relational database management systems (RDBMS) in enterprise environments.

Key Features

ACID Compliance: Ensures data integrity through Atomicity, Consistency, Isolation, and Durability
Multi-version Concurrency Control (MVCC): Allows multiple users to access data concurrently
Partitioning: Divides large tables into smaller, manageable pieces
Advanced Security: Built-in encryption, auditing, and access controls
High Availability: Real Application Clusters (RAC) and Data Guard
Scalability: Supports massive databases and high transaction volumes

Oracle Database Editions

Express Edition (XE): Free, limited version for development and small deployments
Standard Edition: Mid-range edition with core features
Enterprise Edition: Full-featured version with advanced capabilities
Autonomous Database: Cloud-based, self-managing database service

Installation and Setup

Oracle Database Installation

Using Oracle Database XE (Recommended for Development)

Download Oracle Database XE from Oracle’s official website
Install following the platform-specific instructions
Configure the database using Database Configuration Assistant (DBCA)

Docker Installation (Quick Setup)

# Pull Oracle Database XE image
docker pull container-registry.oracle.com/database/express:21.3.0-xe

# Run Oracle Database XE container
docker run --name oracle-xe \
  -p 1521:1521 \
  -p 5500:5500 \
  -e ORACLE_PWD=your_password \
  -e ORACLE_CHARACTERSET=AL32UTF8 \
  container-registry.oracle.com/database/express:21.3.0-xe

Client Tools

SQL*Plus: Command-line interface
SQL Developer: GUI-based development environment
Oracle Enterprise Manager: Web-based management console
DBeaver: Third-party database management tool

Oracle Database Architecture

Physical Architecture

Database Files: Data files, control files, and redo log files
Parameter Files: Configuration settings (PFILE/SPFILE)
Archive Log Files: Backup of redo log files for recovery

Logical Architecture

Tablespaces: Logical storage units containing one or more data files
Schemas: Collection of database objects owned by a user
Segments: Space allocated for database objects
Extents: Contiguous blocks of storage
Blocks: Smallest unit of storage

Memory Architecture

System Global Area (SGA): Shared memory area
- Database Buffer Cache
- Shared Pool
- Redo Log Buffer
- Large Pool
Program Global Area (PGA): Private memory for each process

SQL Fundamentals

Data Definition Language (DDL)

Creating Tables

-- Create a table
CREATE TABLE employees (
    employee_id NUMBER(6) PRIMARY KEY,
    first_name VARCHAR2(20) NOT NULL,
    last_name VARCHAR2(25) NOT NULL,
    email VARCHAR2(50) UNIQUE,
    hire_date DATE DEFAULT SYSDATE,
    job_id VARCHAR2(10),
    salary NUMBER(8,2),
    department_id NUMBER(4),
    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
);

-- Add constraints
ALTER TABLE employees 
ADD CONSTRAINT fk_dept_id 
FOREIGN KEY (department_id) 
REFERENCES departments(department_id);

-- Create index
CREATE INDEX idx_emp_dept ON employees(department_id);

Oracle-Specific Data Types

NUMBER: Numeric data with precision and scale
VARCHAR2: Variable-length character strings
CHAR: Fixed-length character strings
DATE: Date and time
TIMESTAMP: Date and time with fractional seconds
CLOB: Character Large Object
BLOB: Binary Large Object
XMLTYPE: XML data

Data Manipulation Language (DML)

Advanced Queries

-- Window functions
SELECT 
    employee_id,
    first_name,
    last_name,
    salary,
    RANK() OVER (PARTITION BY department_id ORDER BY salary DESC) as salary_rank,
    LAG(salary, 1) OVER (ORDER BY hire_date) as prev_salary
FROM employees;

-- Common Table Expressions (CTE)
WITH dept_avg_salary AS (
    SELECT department_id, AVG(salary) as avg_salary
    FROM employees
    GROUP BY department_id
)
SELECT e.*, d.avg_salary
FROM employees e
JOIN dept_avg_salary d ON e.department_id = d.department_id;

-- Hierarchical queries
SELECT employee_id, first_name, last_name, manager_id, LEVEL
FROM employees
START WITH manager_id IS NULL
CONNECT BY PRIOR employee_id = manager_id
ORDER SIBLINGS BY last_name;

PL/SQL Programming

Basic PL/SQL Block

DECLARE
    v_employee_count NUMBER;
    v_department_name VARCHAR2(30);
BEGIN
    SELECT COUNT(*) INTO v_employee_count
    FROM employees
    WHERE department_id = 10;
    
    IF v_employee_count > 0 THEN
        SELECT department_name INTO v_department_name
        FROM departments
        WHERE department_id = 10;
        
        DBMS_OUTPUT.PUT_LINE('Department: ' || v_department_name || 
                           ' has ' || v_employee_count || ' employees');
    END IF;
EXCEPTION
    WHEN NO_DATA_FOUND THEN
        DBMS_OUTPUT.PUT_LINE('No data found');
    WHEN OTHERS THEN
        DBMS_OUTPUT.PUT_LINE('Error: ' || SQLERRM);
END;
/

Stored Procedures and Functions

-- Stored Procedure
CREATE OR REPLACE PROCEDURE update_employee_salary(
    p_employee_id IN NUMBER,
    p_salary_increase IN NUMBER
) AS
    v_current_salary NUMBER;
BEGIN
    SELECT salary INTO v_current_salary
    FROM employees
    WHERE employee_id = p_employee_id;
    
    UPDATE employees
    SET salary = v_current_salary + p_salary_increase
    WHERE employee_id = p_employee_id;
    
    COMMIT;
EXCEPTION
    WHEN NO_DATA_FOUND THEN
        RAISE_APPLICATION_ERROR(-20001, 'Employee not found');
END;
/

-- Function
CREATE OR REPLACE FUNCTION calculate_annual_salary(
    p_employee_id IN NUMBER
) RETURN NUMBER AS
    v_monthly_salary NUMBER;
BEGIN
    SELECT salary INTO v_monthly_salary
    FROM employees
    WHERE employee_id = p_employee_id;
    
    RETURN v_monthly_salary * 12;
EXCEPTION
    WHEN NO_DATA_FOUND THEN
        RETURN 0;
END;
/

Advanced Oracle Features

Partitioning

-- Range partitioning
CREATE TABLE sales (
    sale_id NUMBER,
    sale_date DATE,
    amount NUMBER
) PARTITION BY RANGE (sale_date) (
    PARTITION p2023 VALUES LESS THAN (DATE '2024-01-01'),
    PARTITION p2024 VALUES LESS THAN (DATE '2025-01-01'),
    PARTITION p_max VALUES LESS THAN (MAXVALUE)
);

-- Hash partitioning
CREATE TABLE customers (
    customer_id NUMBER,
    name VARCHAR2(100)
) PARTITION BY HASH (customer_id) PARTITIONS 4;

Sequences

-- Create sequence
CREATE SEQUENCE emp_seq
    START WITH 1000
    INCREMENT BY 1
    MAXVALUE 9999999
    NOCACHE
    NOCYCLE;

-- Use sequence
INSERT INTO employees (employee_id, first_name, last_name)
VALUES (emp_seq.NEXTVAL, 'John', 'Doe');

Views and Materialized Views

-- Create view
CREATE VIEW employee_details AS
SELECT e.employee_id, e.first_name, e.last_name, 
       d.department_name, e.salary
FROM employees e
JOIN departments d ON e.department_id = d.department_id;

-- Materialized view
CREATE MATERIALIZED VIEW emp_dept_summary
BUILD IMMEDIATE
REFRESH COMPLETE ON DEMAND
AS
SELECT d.department_name, COUNT(*) as employee_count, AVG(salary) as avg_salary
FROM employees e
JOIN departments d ON e.department_id = d.department_id
GROUP BY d.department_name;

Java Database Connectivity

JDBC Driver Setup

Maven Dependencies

<dependency>
    <groupId>com.oracle.database.jdbc</groupId>
    <artifactId>ojdbc11</artifactId>
    <version>23.3.0.23.09</version>
</dependency>

<!-- For connection pooling -->
<dependency>
    <groupId>com.oracle.database.jdbc</groupId>
    <artifactId>ucp</artifactId>
    <version>23.3.0.23.09</version>
</dependency>

Basic JDBC Connection

import java.sql.*;

public class OracleConnection {
    private static final String URL = "jdbc:oracle:thin:@localhost:1521:XE";
    private static final String USERNAME = "your_username";
    private static final String PASSWORD = "your_password";
    
    public static Connection getConnection() throws SQLException {
        return DriverManager.getConnection(URL, USERNAME, PASSWORD);
    }
    
    public static void main(String[] args) {
        try (Connection conn = getConnection()) {
            System.out.println("Connected to Oracle Database!");
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

CRUD Operations

Data Access Object (DAO) Pattern

public class Employee {
    private int employeeId;
    private String firstName;
    private String lastName;
    private String email;
    private Date hireDate;
    private double salary;
    private int departmentId;
    
    // Constructors, getters, and setters
    // ...
}

public interface EmployeeDAO {
    void createEmployee(Employee employee);
    Employee getEmployeeById(int id);
    List<Employee> getAllEmployees();
    void updateEmployee(Employee employee);
    void deleteEmployee(int id);
}

public class EmployeeDAOImpl implements EmployeeDAO {
    private Connection connection;
    
    public EmployeeDAOImpl(Connection connection) {
        this.connection = connection;
    }
    
    @Override
    public void createEmployee(Employee employee) {
        String sql = "INSERT INTO employees (employee_id, first_name, last_name, email, salary, department_id) VALUES (emp_seq.NEXTVAL, ?, ?, ?, ?, ?)";
        
        try (PreparedStatement pstmt = connection.prepareStatement(sql)) {
            pstmt.setString(1, employee.getFirstName());
            pstmt.setString(2, employee.getLastName());
            pstmt.setString(3, employee.getEmail());
            pstmt.setDouble(4, employee.getSalary());
            pstmt.setInt(5, employee.getDepartmentId());
            
            pstmt.executeUpdate();
        } catch (SQLException e) {
            throw new RuntimeException("Error creating employee", e);
        }
    }
    
    @Override
    public Employee getEmployeeById(int id) {
        String sql = "SELECT * FROM employees WHERE employee_id = ?";
        
        try (PreparedStatement pstmt = connection.prepareStatement(sql)) {
            pstmt.setInt(1, id);
            ResultSet rs = pstmt.executeQuery();
            
            if (rs.next()) {
                return mapResultSetToEmployee(rs);
            }
        } catch (SQLException e) {
            throw new RuntimeException("Error retrieving employee", e);
        }
        return null;
    }
    
    @Override
    public List<Employee> getAllEmployees() {
        List<Employee> employees = new ArrayList<>();
        String sql = "SELECT * FROM employees ORDER BY employee_id";
        
        try (Statement stmt = connection.createStatement();
             ResultSet rs = stmt.executeQuery(sql)) {
            
            while (rs.next()) {
                employees.add(mapResultSetToEmployee(rs));
            }
        } catch (SQLException e) {
            throw new RuntimeException("Error retrieving employees", e);
        }
        return employees;
    }
    
    @Override
    public void updateEmployee(Employee employee) {
        String sql = "UPDATE employees SET first_name = ?, last_name = ?, email = ?, salary = ?, department_id = ? WHERE employee_id = ?";
        
        try (PreparedStatement pstmt = connection.prepareStatement(sql)) {
            pstmt.setString(1, employee.getFirstName());
            pstmt.setString(2, employee.getLastName());
            pstmt.setString(3, employee.getEmail());
            pstmt.setDouble(4, employee.getSalary());
            pstmt.setInt(5, employee.getDepartmentId());
            pstmt.setInt(6, employee.getEmployeeId());
            
            pstmt.executeUpdate();
        } catch (SQLException e) {
            throw new RuntimeException("Error updating employee", e);
        }
    }
    
    @Override
    public void deleteEmployee(int id) {
        String sql = "DELETE FROM employees WHERE employee_id = ?";
        
        try (PreparedStatement pstmt = connection.prepareStatement(sql)) {
            pstmt.setInt(1, id);
            pstmt.executeUpdate();
        } catch (SQLException e) {
            throw new RuntimeException("Error deleting employee", e);
        }
    }
    
    private Employee mapResultSetToEmployee(ResultSet rs) throws SQLException {
        Employee employee = new Employee();
        employee.setEmployeeId(rs.getInt("employee_id"));
        employee.setFirstName(rs.getString("first_name"));
        employee.setLastName(rs.getString("last_name"));
        employee.setEmail(rs.getString("email"));
        employee.setHireDate(rs.getDate("hire_date"));
        employee.setSalary(rs.getDouble("salary"));
        employee.setDepartmentId(rs.getInt("department_id"));
        return employee;
    }
}

Working with Stored Procedures

public class StoredProcedureExample {
    
    public void updateEmployeeSalary(int employeeId, double salaryIncrease) {
        String sql = "{call update_employee_salary(?, ?)}";
        
        try (Connection conn = OracleConnection.getConnection();
             CallableStatement cstmt = conn.prepareCall(sql)) {
            
            cstmt.setInt(1, employeeId);
            cstmt.setDouble(2, salaryIncrease);
            cstmt.execute();
            
        } catch (SQLException e) {
            throw new RuntimeException("Error calling stored procedure", e);
        }
    }
    
    public double getAnnualSalary(int employeeId) {
        String sql = "{? = call calculate_annual_salary(?)}";
        
        try (Connection conn = OracleConnection.getConnection();
             CallableStatement cstmt = conn.prepareCall(sql)) {
            
            cstmt.registerOutParameter(1, Types.NUMERIC);
            cstmt.setInt(2, employeeId);
            cstmt.execute();
            
            return cstmt.getDouble(1);
            
        } catch (SQLException e) {
            throw new RuntimeException("Error calling function", e);
        }
    }
}

Connection Management

Connection Pooling with Oracle UCP

import oracle.ucp.jdbc.PoolDataSource;
import oracle.ucp.jdbc.PoolDataSourceFactory;

public class ConnectionPoolManager {
    private static PoolDataSource poolDataSource;
    
    static {
        try {
            poolDataSource = PoolDataSourceFactory.getPoolDataSource();
            poolDataSource.setURL("jdbc:oracle:thin:@localhost:1521:XE");
            poolDataSource.setUser("your_username");
            poolDataSource.setPassword("your_password");
            poolDataSource.setConnectionFactoryClassName("oracle.jdbc.pool.OracleDataSource");
            
            // Pool configuration
            poolDataSource.setInitialPoolSize(5);
            poolDataSource.setMinPoolSize(5);
            poolDataSource.setMaxPoolSize(20);
            poolDataSource.setConnectionWaitTimeout(5);
            poolDataSource.setInactiveConnectionTimeout(300);
            
        } catch (SQLException e) {
            throw new RuntimeException("Error initializing connection pool", e);
        }
    }
    
    public static Connection getConnection() throws SQLException {
        return poolDataSource.getConnection();
    }
}

Transaction Management

public class TransactionExample {
    
    public void transferFunds(int fromAccount, int toAccount, double amount) {
        Connection conn = null;
        try {
            conn = ConnectionPoolManager.getConnection();
            conn.setAutoCommit(false); // Start transaction
            
            // Debit from source account
            String debitSql = "UPDATE accounts SET balance = balance - ? WHERE account_id = ?";
            try (PreparedStatement debitStmt = conn.prepareStatement(debitSql)) {
                debitStmt.setDouble(1, amount);
                debitStmt.setInt(2, fromAccount);
                debitStmt.executeUpdate();
            }
            
            // Credit to destination account
            String creditSql = "UPDATE accounts SET balance = balance + ? WHERE account_id = ?";
            try (PreparedStatement creditStmt = conn.prepareStatement(creditSql)) {
                creditStmt.setDouble(1, amount);
                creditStmt.setInt(2, toAccount);
                creditStmt.executeUpdate();
            }
            
            conn.commit(); // Commit transaction
            
        } catch (SQLException e) {
            if (conn != null) {
                try {
                    conn.rollback(); // Rollback on error
                } catch (SQLException ex) {
                    ex.printStackTrace();
                }
            }
            throw new RuntimeException("Error in fund transfer", e);
        } finally {
            if (conn != null) {
                try {
                    conn.setAutoCommit(true); // Reset auto-commit
                    conn.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}

ORM Frameworks

Hibernate Configuration

<!-- hibernate.cfg.xml -->
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-configuration PUBLIC
    "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
    "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
    <session-factory>
        <property name="hibernate.connection.driver_class">oracle.jdbc.OracleDriver</property>
        <property name="hibernate.connection.url">jdbc:oracle:thin:@localhost:1521:XE</property>
        <property name="hibernate.connection.username">your_username</property>
        <property name="hibernate.connection.password">your_password</property>
        <property name="hibernate.dialect">org.hibernate.dialect.Oracle12cDialect</property>
        <property name="hibernate.hbm2ddl.auto">update</property>
        <property name="hibernate.show_sql">true</property>
        <property name="hibernate.format_sql">true</property>
        
        <!-- Connection pool -->
        <property name="hibernate.c3p0.min_size">5</property>
        <property name="hibernate.c3p0.max_size">20</property>
        <property name="hibernate.c3p0.timeout">300</property>
        <property name="hibernate.c3p0.max_statements">50</property>
        <property name="hibernate.c3p0.idle_test_period">3000</property>
    </session-factory>
</hibernate-configuration>

JPA Entity with Oracle-specific Features

@Entity
@Table(name = "employees")
@SequenceGenerator(name = "emp_seq", sequenceName = "emp_seq", allocationSize = 1)
public class Employee {
    
    @Id
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "emp_seq")
    @Column(name = "employee_id")
    private Integer employeeId;
    
    @Column(name = "first_name", nullable = false, length = 20)
    private String firstName;
    
    @Column(name = "last_name", nullable = false, length = 25)
    private String lastName;
    
    @Column(name = "email", unique = true, length = 50)
    private String email;
    
    @Column(name = "hire_date")
    @Temporal(TemporalType.DATE)
    private Date hireDate;
    
    @Column(name = "salary", precision = 8, scale = 2)
    private BigDecimal salary;
    
    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "department_id")
    private Department department;
    
    @CreationTimestamp
    @Column(name = "created_at")
    private Timestamp createdAt;
    
    @UpdateTimestamp
    @Column(name = "updated_at")
    private Timestamp updatedAt;
    
    // Constructors, getters, and setters
    // ...
}

Spring Boot with Oracle

# application.yml
spring:
  datasource:
    url: jdbc:oracle:thin:@localhost:1521:XE
    username: your_username
    password: your_password
    driver-class-name: oracle.jdbc.OracleDriver
    hikari:
      minimum-idle: 5
      maximum-pool-size: 20
      idle-timeout: 300000
      max-lifetime: 1800000
      connection-timeout: 30000
      
  jpa:
    hibernate:
      ddl-auto: update
    show-sql: true
    properties:
      hibernate:
        dialect: org.hibernate.dialect.Oracle12cDialect
        format_sql: true
        jdbc:
          batch_size: 20
        order_inserts: true
        order_updates: true

Performance Optimization

Query Optimization

-- Use indexes effectively
CREATE INDEX idx_emp_dept_salary ON employees(department_id, salary);

-- Use hints when necessary
SELECT /*+ INDEX(e idx_emp_dept_salary) */ 
       e.employee_id, e.first_name, e.last_name
FROM employees e
WHERE department_id = 10 AND salary > 50000;

-- Use bind variables to prevent SQL injection and improve performance
SELECT * FROM employees WHERE employee_id = :employee_id;

Java Performance Tips

// Use batch processing for multiple inserts
public void batchInsertEmployees(List<Employee> employees) {
    String sql = "INSERT INTO employees (employee_id, first_name, last_name, email, salary, department_id) VALUES (emp_seq.NEXTVAL, ?, ?, ?, ?, ?)";
    
    try (Connection conn = ConnectionPoolManager.getConnection();
         PreparedStatement pstmt = conn.prepareStatement(sql)) {
        
        conn.setAutoCommit(false);
        
        for (Employee emp : employees) {
            pstmt.setString(1, emp.getFirstName());
            pstmt.setString(2, emp.getLastName());
            pstmt.setString(3, emp.getEmail());
            pstmt.setDouble(4, emp.getSalary());
            pstmt.setInt(5, emp.getDepartmentId());
            pstmt.addBatch();
        }
        
        pstmt.executeBatch();
        conn.commit();
        
    } catch (SQLException e) {
        throw new RuntimeException("Error in batch insert", e);
    }
}

// Use proper fetch sizes for large result sets
public List<Employee> getAllEmployeesOptimized() {
    List<Employee> employees = new ArrayList<>();
    String sql = "SELECT * FROM employees ORDER BY employee_id";
    
    try (Connection conn = ConnectionPoolManager.getConnection();
         PreparedStatement pstmt = conn.prepareStatement(sql)) {
        
        pstmt.setFetchSize(1000); // Optimize fetch size
        ResultSet rs = pstmt.executeQuery();
        
        while (rs.next()) {
            employees.add(mapResultSetToEmployee(rs));
        }
        
    } catch (SQLException e) {
        throw new RuntimeException("Error retrieving employees", e);
    }
    return employees;
}

Security Best Practices

Connection Security

// Use encrypted connections
String url = "jdbc:oracle:thin:@(DESCRIPTION=(ADDRESS=(PROTOCOL=tcps)(HOST=localhost)(PORT=2484))(CONNECT_DATA=(SERVICE_NAME=XE)))" +
            "?oracle.net.ssl_client_authentication=false" +
            "&oracle.net.ssl_server_cert_dn=\"CN=localhost\"";

// Use connection properties for security
Properties props = new Properties();
props.setProperty("user", username);
props.setProperty("password", password);
props.setProperty("oracle.net.encryption_client", "REQUIRED");
props.setProperty("oracle.net.encryption_types_client", "AES256");
props.setProperty("oracle.net.crypto_checksum_client", "REQUIRED");
props.setProperty("oracle.net.crypto_checksum_types_client", "SHA256");

Connection conn = DriverManager.getConnection(url, props);

SQL Injection Prevention

// Always use parameterized queries
public Employee findEmployeeByEmail(String email) {
    String sql = "SELECT * FROM employees WHERE email = ?"; // Safe
    // String sql = "SELECT * FROM employees WHERE email = '" + email + "'"; // DANGEROUS!
    
    try (Connection conn = ConnectionPoolManager.getConnection();
         PreparedStatement pstmt = conn.prepareStatement(sql)) {
        
        pstmt.setString(1, email);
        ResultSet rs = pstmt.executeQuery();
        
        if (rs.next()) {
            return mapResultSetToEmployee(rs);
        }
        
    } catch (SQLException e) {
        throw new RuntimeException("Error finding employee", e);
    }
    return null;
}

Monitoring and Maintenance

Database Monitoring Queries

-- Check table sizes
SELECT table_name, 
       ROUND(((num_rows * avg_row_len) / 1024 / 1024), 2) as size_mb
FROM user_tables
ORDER BY size_mb DESC;

-- Monitor active sessions
SELECT username, osuser, machine, program, status, logon_time
FROM v$session
WHERE username IS NOT NULL
ORDER BY logon_time;

-- Check tablespace usage
SELECT tablespace_name,
       ROUND(((total_bytes - free_bytes) / 1024 / 1024), 2) as used_mb,
       ROUND((free_bytes / 1024 / 1024), 2) as free_mb,
       ROUND(((total_bytes - free_bytes) / total_bytes * 100), 2) as percent_used
FROM (
    SELECT tablespace_name, SUM(bytes) as total_bytes
    FROM dba_data_files
    GROUP BY tablespace_name
) total,
(
    SELECT tablespace_name, SUM(bytes) as free_bytes
    FROM dba_free_space
    GROUP BY tablespace_name
) free
WHERE total.tablespace_name = free.tablespace_name(+);

Application Monitoring

// Connection pool monitoring
public class ConnectionPoolMonitor {
    
    public void printPoolStatistics() {
        try {
            oracle.ucp.jdbc.PoolDataSource pds = (oracle.ucp.jdbc.PoolDataSource) poolDataSource;
            
            System.out.println("=== Connection Pool Statistics ===");
            System.out.println("Available Connections: " + pds.getAvailableConnectionsCount());
            System.out.println("Borrowed Connections: " + pds.getBorrowedConnectionsCount());
            System.out.println("Peak Pool Size: " + pds.getPeakPoolSize());
            System.out.println("Connection Pool Size: " + pds.getPoolSize());
            System.out.println("================================");
            
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

// Query performance monitoring
public class QueryPerformanceMonitor {
    
    public <T> T executeWithTiming(String operationName, Supplier<T> operation) {
        long startTime = System.currentTimeMillis();
        
        try {
            T result = operation.get();
            long duration = System.currentTimeMillis() - startTime;
            
            System.out.println(operationName + " executed in " + duration + "ms");
            
            if (duration > 1000) { // Log slow queries
                System.out.println("SLOW QUERY DETECTED: " + operationName);
            }
            
            return result;
            
        } catch (Exception e) {
            System.err.println("Error in " + operationName + ": " + e.getMessage());
            throw e;
        }
    }
}

Best Practices Summary

Database Design

Use appropriate data types and constraints
Implement proper indexing strategy
Consider partitioning for large tables
Use sequences for primary keys
Normalize data appropriately

Java Development

Always use connection pooling
Implement proper exception handling
Use parameterized queries to prevent SQL injection
Close resources properly (use try-with-resources)
Consider using ORM frameworks for complex applications

Performance

Monitor and optimize slow queries
Use batch operations for bulk data operations
Implement proper caching strategies
Monitor connection pool metrics
Use appropriate fetch sizes

Security

Use encrypted connections in production
Implement proper authentication and authorization
Never hardcode credentials
Use principle of least privilege
Regular security audits

This comprehensive guide provides a solid foundation for working with Oracle Database in Java applications. Remember to always refer to the official Oracle documentation for the most up-to-date information and best practices.

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