ResultSet Navigation and Mapping Rows to Java Domain Models0%

Transaction Management: setAutoCommit(false), commit(), and rollback()

ResultSet Navigation and Mapping Rows to Java Domain Models

Advanced15 min read•Updated: 2025-01-15

Introduction

When a query executes via executeQuery(), the database returns a ResultSet. A ResultSet maintains an internal cursor pointing to the current row of data. Navigating this cursor and mapping relational tabular columns to strongly typed Java domain models (POJOs or Records) is the core responsibility of the Data Access Object (DAO) layer.

🔄 Cursor Mechanics

Initially, the ResultSet cursor is positioned before the first row. Calling .next() moves the cursor forward to the next record:

1                  [ Before First Row ]  <-- Initial Position
2rs.next() ──────► Row 1: [ ID=101 | Name="Aarav" | Marks=92.5 ]
3rs.next() ──────► Row 2: [ ID=102 | Name="Neha"  | Marks=88.0 ]
4rs.next() ──────► Row 3: [ ID=103 | Name="Rohit" | Marks=76.2 ]
5rs.next() ──────► [ After Last Row ]   <-- Returns false, loop terminates

💻 Clean DAO Mapping Pattern

1package com.mskinstitute.dao;
2 
3import java.sql.*;
4import java.util.ArrayList;
5import java.util.List;
6 
7// Immutable Java Record Domain Model
8public record StudentRecord(int id, String name, String email, double gpa) {}
9 
10public class StudentDAO {
11    private final Connection connection;
12 
13    public StudentDAO(Connection connection) {
14        this.connection = connection;
15    }
16 
17    public List<StudentRecord> findAllHonorsStudents(double minGpa) throws SQLException {
18        String sql = "SELECT id, full_name, email, gpa FROM students WHERE gpa >= ? ORDER BY gpa DESC";
19        List<StudentRecord> students = new ArrayList<>();
20 
21        try (PreparedStatement pstmt = connection.prepareStatement(sql)) {
22            pstmt.setDouble(1, minGpa);
23 
24            try (ResultSet rs = pstmt.executeQuery()) {
25                while (rs.next()) {
26                    // Extract columns by name (clean and refactor-safe)
27                    int id = rs.getInt("id");
28                    String name = rs.getString("full_name");
29                    String email = rs.getString("email");
30                    double gpa = rs.getDouble("gpa");
31 
32                    students.add(new StudentRecord(id, name, email, gpa));
33                }
34            }
35        }
36        return students;
37    }
38}

Next Lesson

Transaction Management: setAutoCommit(false), commit(), and rollback()

Continue learning with hands-on practice, examples, and exercises in the upcoming topic.

Related Lessons

Previous Lesson	Next Lesson
Executing Queries: Statement vs PreparedStatement (SQL Injection Prevention)	Transaction Management: setAutoCommit(false), commit(), and rollback()

Practice Quiz

Test your understanding of this lesson with 1 questions. Each question has one correct answer.

Previous Next

PreviousPrevNext

MSK Institute • Shikohabad

Loading Page Content...

Preparing courses, live labs, and learning resources.सामग्री लोड हो रही है, कृपया प्रतीक्षा करें...

Connecting serverPlease wait...

💻 Practical Labs🚀 Free Demo📜 Verified Certificates

Transaction Management: setAutoCommit(false), commit(), and rollback()

ResultSet Navigation and Mapping Rows to Java Domain Models

Advanced15 min read•Updated: 2025-01-15

Study Materials

Introduction

🔄 Cursor Mechanics

Initially, the ResultSet cursor is positioned before the first row. Calling .next() moves the cursor forward to the next record:

1                  [ Before First Row ]  <-- Initial Position
2rs.next() ──────► Row 1: [ ID=101 | Name="Aarav" | Marks=92.5 ]
3rs.next() ──────► Row 2: [ ID=102 | Name="Neha"  | Marks=88.0 ]
4rs.next() ──────► Row 3: [ ID=103 | Name="Rohit" | Marks=76.2 ]
5rs.next() ──────► [ After Last Row ]   <-- Returns false, loop terminates

💻 Clean DAO Mapping Pattern

1package com.mskinstitute.dao;
2 
3import java.sql.*;
4import java.util.ArrayList;
5import java.util.List;
6 
7// Immutable Java Record Domain Model
8public record StudentRecord(int id, String name, String email, double gpa) {}
9 
10public class StudentDAO {
11    private final Connection connection;
12 
13    public StudentDAO(Connection connection) {
14        this.connection = connection;
15    }
16 
17    public List<StudentRecord> findAllHonorsStudents(double minGpa) throws SQLException {
18        String sql = "SELECT id, full_name, email, gpa FROM students WHERE gpa >= ? ORDER BY gpa DESC";
19        List<StudentRecord> students = new ArrayList<>();
20 
21        try (PreparedStatement pstmt = connection.prepareStatement(sql)) {
22            pstmt.setDouble(1, minGpa);
23 
24            try (ResultSet rs = pstmt.executeQuery()) {
25                while (rs.next()) {
26                    // Extract columns by name (clean and refactor-safe)
27                    int id = rs.getInt("id");
28                    String name = rs.getString("full_name");
29                    String email = rs.getString("email");
30                    double gpa = rs.getDouble("gpa");
31 
32                    students.add(new StudentRecord(id, name, email, gpa));
33                }
34            }
35        }
36        return students;
37    }
38}

Next Lesson

Transaction Management: setAutoCommit(false), commit(), and rollback()

Continue learning with hands-on practice, examples, and exercises in the upcoming topic.

Related Lessons

Previous Lesson	Next Lesson
Executing Queries: Statement vs PreparedStatement (SQL Injection Prevention)	Transaction Management: setAutoCommit(false), commit(), and rollback()

Practice Quiz

Test your understanding of this lesson with 1 questions. Each question has one correct answer.

Previous Next

ResultSet Navigation and Mapping Rows to Java Domain Models

📋 ResultSet Navigation and Mapping Rows to Java Domain Models

Introduction

🔄 Cursor Mechanics

💻 Clean DAO Mapping Pattern

Transaction Management: setAutoCommit(false), commit(), and rollback()

Related Lessons

Practice Quiz

Loading Page Content...

ResultSet Navigation and Mapping Rows to Java Domain Models

📋 ResultSet Navigation and Mapping Rows to Java Domain Models

Introduction

🔄 Cursor Mechanics

💻 Clean DAO Mapping Pattern

Transaction Management: setAutoCommit(false), commit(), and rollback()

Related Lessons

Practice Quiz