Question

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我正在尝试插入数据库表＆＃39; dotcom＆＃39;来自文本文件的4列5000行数据，格式为[x，w，x，y，z]，例如

1 google com null null

2 google co uk null

...

并且返回的行仍然是＆＃39; 1＆＃39;而不是＆＃39; 5000＆＃39;由于某些原因。

问题是即使BufferedReader读取了行，也不会将行插入数据库表中。我该如何解决这个问题？例如。使用循环将数据插入表中？

非常感谢任何帮助！

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

在循环的每次迭代中，您都会覆盖numRows，而不是使用新添加的行递增它。只需将=替换为+=，您就可以了：

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

话虽如此，你应该真正研究PreparedStatement和executing batches。

PostgreSQL：如何使用循环将数据插入数据库表？

1 个答案: