PostgreSQL：如何通过循环将数据插入数据库表？

Question

Hello fellow Stackoverflowers!

I am trying to INSERT INTO a database table 'dotcom' 4 columns of 5000 rows of data from a text file in the form [x, w, x, y, z] eg

1 google com null null

2 google co uk null

...

and the rows returned remains '1' instead of '5000' for some reason.

The problem is that the rows are not inserted into the database table even though the BufferedReader reads it. How may I solve this problem? Eg inserting the data into the table with a loop?

Any help would be greatly appreciated!

import java.sql.*;
import java.util.Scanner;
import java.io.*;

public class Database {

    public static Connection connectToDatabase(String user, String port,
            String database) {
        System.out.println("-------- PostgreSQL JDBC Connection Testing ------------");
        try {
            Class.forName("org.postgresql.Driver");
        } catch (ClassNotFoundException e) {

            System.out.println("Where is your PostgreSQL JDBC Driver? " + "Include in your library path!");
            e.printStackTrace();
        }
        System.out.println("PostgreSQL JDBC Driver Registered!");

        Connection connection = null;
        try {
            connection = DriverManager.getConnection("jdbc:postgresql://localhost:" + port + "/" + database, user, "doesn't matter!");
        } catch (SQLException e) {
            System.out.println("Connection Failed! Check output console");
            e.printStackTrace();
        }
        return connection;
    }

    public static ResultSet executeSelect(Connection connection, String query) {
        Statement st = null;
        try {
            st = connection.createStatement();
        } catch (SQLException e) {
            e.printStackTrace();
            return null;
        }

        ResultSet rs = null;
        try {
            rs = st.executeQuery(query);
            //st.close();
        } catch (SQLException e) {
            e.printStackTrace();
            return null;
        }

        return rs;
    }

    public static void dropTable(Connection connection, String table) {
        Statement st = null;
        try {
            st = connection.createStatement();
            st.execute("DROP TABLE " + table);
            st.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    public static void createTable(Connection connection,
            String tableDescription) {
        Statement st = null;
        try {
            st = connection.createStatement();
            st.execute("CREATE TABLE " + tableDescription);
            st.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    public static int insertIntoTableFromFile(Connection connection,
            String table, String file) {

        BufferedReader br = null;
        int numRows = 0;
        try {
            Statement st = connection.createStatement();
            String sCurrentLine, brokenLine[], composedLine = "";
            br = new BufferedReader(new FileReader("src/TopURLs"));

            while ((sCurrentLine = br.readLine()) != null) {
                // Insert each line to the DB
                brokenLine = sCurrentLine.split("\t");
                composedLine = "INSERT INTO dotcom VALUES (";
                int i;
                for (i = 0; i < brokenLine.length - 1; i++) {
                    composedLine += "'" + brokenLine[i] + "',";
                }
                composedLine += "'" + brokenLine[i] + "')";
                numRows = st.executeUpdate(composedLine);
                //System.out.println(composedLine);
            }
        } catch (IOException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            try {
                if (br != null)
                    br.close();
            } catch (IOException ex) {
                ex.printStackTrace();
            }
        }
        return numRows;
    }

    public static void main(String[] argv) throws SQLException {
        /*
        Scanner input = new Scanner(System.in);
        System.out.println("Please enter your Username:");
        String user = input.next();
        System.out.println("Please enter your Port ID:");
        String port = input.next();
        */

        String user = "zbva777";
        String port = "28046";
        String database = "test";

        Connection connection = connectToDatabase(user, port, database);

        if (connection != null) {
            System.out.println("You made it, take control your database now!");
        } else {
            System.out.println("Failed to make connection!");
            return;
        }
        // Now we're ready to work on the DB

        String query = "SELECT * FROM dotcom";
        ResultSet rs = executeSelect(connection, query);
        try {
            while (rs.next()) {
                System.out.print("Column 1 returned ");
                System.out.println(rs.getString(1));
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
        rs.close();

        dropTable(connection, "dotcom");
        createTable(connection, "dotcom (rank int primary key, name varchar(5000), type varchar(5000), subtype varchar(5000), subsubtype varchar(5000));");
        int rows = insertIntoTableFromFile(connection, "dotcom", "src/TopURLs");
        System.out.println(rows + " rows inserted.");
    }
}

Answer 1

In each iteration of the loop you override numRows instead of incrementing it with the newly added row. Just replace the = with += and you should be OK:

numRows += st.executeUpdate(composedLine);
// Here ^

That being said, you should really look into PreparedStatement s and executing batches .