FetchTableDataServlet Rest API

To use the FetchTableDataServlet follow these steps:

1. Set up your project and servlet environment

• Ensure that your servlet container (e.g., Apache Tomcat) is running and properly configured.
• If you haven’t done so, make sure your Java project is set up with the appropriate libraries for servlets and database connectivity (e.g., JDBC, JSON processing, etc.).

2. Deploy the servlet

• The servlet is mapped to /fetchTableData using the @WebServlet annotation. This means that it will respond to HTTP requests made to http://<server_address>/fetchTableData.
• Ensure your servlet is deployed in your web application and that it can be accessed.

3. Testing the Servlet

You can test the FetchTableDataServlet by sending HTTP requests (GET, POST, PUT, DELETE) to it.

Here’s how you can use the servlet with examples of different HTTP methods.

4. Example of how to use the servlet with different HTTP methods

GET Method – Fetch Data

You can use this method to fetch data from the specified table in your database.

Example Request:

GET http://<your_server>/fetchTableData
Content-Type: application/json

{
    "table_name": "your_table_name"
}

Expected Response:

{
    "status": "success",
    "data": [
        {
            "id": 1,
            "name": "John Doe",
            "age": 30
        },
        {
            "id": 2,
            "name": "Jane Smith",
            "age": 25
        }
    ]
}

POST Method – Insert Data

You can use this method to insert a new row into the specified table.

Example Request:

POST http://<your_server>/fetchTableData
Content-Type: application/json

{
    "table_name": "your_table_name",
    "row": {
        "name": "Alice",
        "age": 28
    }
}

Expected Response:

{
    "status": "success",
    "message": "Row inserted successfully."
}

PUT Method – Update Data

You can use this method to update a row in the specified table. Make sure you provide the id of the row you want to update.

Example Request:

PUT http://<your_server>/fetchTableData
Content-Type: application/json

{
    "table_name": "your_table_name",
    "id": 1,
    "row": {
        "name": "John Doe Updated",
        "age": 31
    }
}

Expected Response:

{
    "status": "success",
    "message": "Row updated successfully."
}

DELETE Method – Delete Data

You can use this method to delete a row from the specified table.

Example Request:

DELETE http://<your_server>/fetchTableData
Content-Type: application/json

{
    "table_name": "your_table_name",
    "id": 1
}

Expected Response:

{
    "status": "success",
    "message": "Row deleted successfully."
}

5. Sending Requests

You can send the requests using any HTTP client, such as:

• Postman: A popular tool for sending HTTP requests and testing APIs.
• Curl: A command-line tool for making HTTP requests.
• JavaScript (Fetch API): For sending requests from a frontend application.

6. Sample JavaScript Example (using Fetch API)

Here’s how you could use the FetchTableDataServlet with JavaScript (using the Fetch API):

// Function to fetch data (GET request)
fetch('http://localhost:8080/fetchTableData', {
    method: 'GET',
    headers: {
        'Content-Type': 'application/json',
    },
    body: JSON.stringify({
        table_name: 'your_table_name'
    })
})
.then(response => response.json())
.then(data => {
    console.log('Data fetched:', data);
})
.catch(error => console.error('Error fetching data:', error));


// Function to insert data (POST request)
fetch('http://localhost:8080/fetchTableData', {
    method: 'POST',
    headers: {
        'Content-Type': 'application/json',
    },
    body: JSON.stringify({
        table_name: 'your_table_name',
        row: {
            name: 'Alice',
            age: 28
        }
    })
})
.then(response => response.json())
.then(data => {
    console.log('Data inserted:', data);
})
.catch(error => console.error('Error inserting data:', error));

7. Database Configuration

Make sure your database connection is configured correctly in your DatabaseConnection.getConnection() method. The servlet relies on the DatabaseConnection class to handle database connections, so ensure this class has the proper JDBC setup (connection URL, username, password, etc.) to connect to your database.

8. Security Considerations

• SQL Injection Prevention: The table name is validated to prevent SQL injection. However, you should also be careful about any dynamic queries and validate the data properly.
• Authentication/Authorization: Depending on your application, you may need to secure your servlet by adding authentication and authorization layers (e.g., using session tokens or JWT).

9. Error Handling

If anything goes wrong (e.g., invalid table name, database connection error), the servlet responds with a JSON error message:

{
    "status": "error",
    "message": "Detailed error message here"
}

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By following the steps above, you should be able to successfully interact with the FetchTableDataServlet using different HTTP methods for CRUD operations.