如果在使用mysql数据库的简单java应用程序中输入超过1个单词，则用户输入会产生错误

zaqlnxep  于 2021-07-14  发布在  Java
关注(0)|答案(0)|浏览(175)

我只是在学习sql，这是我的第一个任务，将它整合到java应用程序中。我有问题，由用户输入多个字，它打破了。如果我只在word上输入没有空格的单词，一切都会很好。我真的很感激你的帮助！
下面是一些错误的截图（可能与扫描仪有关，但就我的生命而言，我无法修复它！）代码如下。
如果我键入2个单词，则会同时显示以下2个.next（）。
但如果我只打一个字，它就不会断。
按标题“搜索”也一样，如果键入多个单词，则会出现以下错误。

  1. import java.sql.Connection;
  2. import java.sql.DriverManager;
  3. import java.sql.PreparedStatement;
  4. import java.sql.SQLException;
  5. import java.sql.ResultSet;
  6. import java.sql.Statement;
  7. import java.util.*;
  9. // This is a simple bookstore application that allows the user to add, update, 
  10. // delete and search for books in the MySQL database.
  12. // Book class
  13. class Books {
  14.     public int id;
  15.     public String title;
  16.     public String author;
  17.     public int qty;
  18.     public String search;
  20.     public Books() {
  21.     }
  23.     public Books(int id, String title, String author, int qty) {
  24.         this.id = id;
  25.         this.title = title;
  26.         this.author = author;
  27.         this.qty = qty;
  28.     }
  29. }
  31. // BookStore Class
  32. public class BookStore {
  33.     public int choice;
  34.     static int id = 0;
  35.     static String title = "";
  36.     static String author = "";
  37.     static int qty = 0;
  39.     public static void main(String[] args) throws SQLException {
  40.         boolean quit = false;
  41.         Scanner input = new Scanner(System.in);
  42.         int menu = 0;
  44.         System.out.println("Betty's Book Store\n-----------------------------");
  46.         // SQL details
  47.         String url = "jdbc:mysql://localhost:3306/ebookstore_db?useSSL=false";
  48.         String user = "otheruser";
  49.         String password = "swordfish";
  51.         PreparedStatement myStmt = null;
  52.         Connection myConn = null;
  54.         do {
  55.             // Menu
  56.             System.out.println();
  57.             System.out.println("1. Enter book");
  58.             System.out.println("2. Update book");
  59.             System.out.println("3. Delete book");
  60.             System.out.println("4. Search books");
  61.             System.out.println("5. Exit");
  63.             System.out.print("\nPlease enter your choice: ");
  64.             menu = input.nextInt();
  65.             System.out.println();
  66.             switch (menu) {
  68.             case 1:
  69.                 System.out.println("1. Enter book\n-----------------------------");
  71.                 try {
  72.                     // Add a new book
  73.                     System.out.print("Book ID: ");
  74.                     int id = input.nextInt();
  76.                     System.out.print("Book Title: ");
  77.                     String title = input.next();
  79.                     System.out.print("Book Author: ");
  80.                     String author = input.next();
  82.                     System.out.print("Quantity: ");
  83.                     int qty = input.nextInt();
  85.                     // 1. Get a connection to database
  86.                     myConn = DriverManager.getConnection(url, user, password);
  88.                     // 2. Create a statement
  89.                     String sql = "INSERT INTO books " + " (id, title, author, qty)" + " values (?, ?, ?, ?)";
  91.                     myStmt = myConn.prepareStatement(sql);
  93.                     // Set parameter values
  94.                     myStmt.setInt(1, id);
  95.                     myStmt.setString(2, title);
  96.                     myStmt.setString(3, author);
  97.                     myStmt.setInt(4, qty);
  99.                     // 3. Execute SQL query
  100.                     myStmt.executeUpdate();
  102.                     System.out.println("Insert complete.");
  103.                     printAllFromTable(myStmt);
  105.                 } catch (Exception exc) {
  106.                     exc.printStackTrace();
  108.                 } finally {
  109.                     if (myStmt != null) {
  110.                         myStmt.close();
  111.                     }
  113.                     if (myConn != null) {
  114.                         myConn.close();
  115.                     }
  116.                 }
  118.                 break;
  120.             case 2:
  121.                 // Update a book's data
  122.                 System.out.println("2. Update book\n-----------------------------");
  124.                 try {
  125.                     // Search for book by ID
  126.                     System.out.print("Enter Book ID: ");
  127.                     int searchId = input.nextInt();
  128.                     int id = searchId;
  129.                     ResultSet results;
  131.                     // 1. Get a connection to database
  132.                     myConn = DriverManager.getConnection(url, user, password);
  134.                     // 2. Create a statement
  135.                     String sql = "SELECT * FROM books WHERE id = ?";
  136.                     myStmt = myConn.prepareStatement(sql);
  138.                     // Set parameter values
  139.                     myStmt.setInt(1, id);
  141.                     // Set parameter values
  142.                     myStmt.setInt(1, id);
  144.                     // 3. Execute SQL query
  145.                     results = myStmt.executeQuery();
  147.                     // Loop over the results, printing them all.
  148.                     while (results.next()) {
  149.                         System.out.println(results.getInt("id") + ", " + results.getString("title") + ", "
  150.                                 + results.getString("author") + ", " + results.getInt("qty") + "\n");
  151.                     }
  153.                     // Close up our connections
  154.                     results.close();
  156.                     // Sub menu for updating book data after selecting ID
  157.                     System.out.println("1. Update ID");
  158.                     System.out.println("2. Update Title");
  159.                     System.out.println("3. Update Author");
  160.                     System.out.println("4. Update Quantity");
  161.                     System.out.println("5. Main menu");
  163.                     do {
  164.                         System.out.print("\nPlease enter your choice: ");
  165.                         menu = input.nextInt();
  166.                         System.out.println();
  167.                         switch (menu) {
  169.                         case 1:
  170.                             try {
  171.                                 // Update Book ID
  172.                                 System.out.print("Enter New ID: ");
  173.                                 int updateId = input.nextInt();
  174.                                 int id2 = updateId;
  176.                                 // 1. Get a connection to database
  177.                                 myConn = DriverManager.getConnection(url, user, password);
  179.                                 // 2. Create a statement
  180.                                 String sql1 = "UPDATE books SET id = ? WHERE id = ?";
  181.                                 myStmt = myConn.prepareStatement(sql1);
  183.                                 // Set parameter values
  184.                                 myStmt.setInt(1, id2);
  185.                                 myStmt.setInt(2, id);
  187.                                 // 3. Execute SQL query
  188.                                 myStmt.execute();
  190.                                 System.out.println("ID updated.");
  191.                                 printAllFromTable(myStmt);
  193.                             } catch (Exception exc) {
  194.                                 exc.printStackTrace();
  196.                             } finally {
  197.                                 if (myStmt != null) {
  198.                                     myStmt.close();
  199.                                 }
  201.                                 if (myConn != null) {
  202.                                     myConn.close();
  203.                                 }
  204.                             }
  205.                             break;
  207.                         case 2:
  208.                             try {
  209.                                 // Update Book title
  210.                                 System.out.print("Enter New Title: ");
  211.                                 String title = input.next();
  213.                                 // 1. Get a connection to database
  214.                                 myConn = DriverManager.getConnection(url, user, password);
  216.                                 // 2. Create a statement
  217.                                 String sql1 = "UPDATE books SET title = ? WHERE id = ?";
  218.                                 myStmt = myConn.prepareStatement(sql1);
  220.                                 // Set parameter values
  221.                                 myStmt.setString(1, title);
  222.                                 myStmt.setInt(2, id);
  224.                                 // 3. Execute SQL query
  225.                                 myStmt.execute();
  227.                                 System.out.println("Title updated.");
  228.                                 printAllFromTable(myStmt);
  230.                             } catch (Exception exc) {
  231.                                 exc.printStackTrace();
  233.                             } finally {
  234.                                 if (myStmt != null) {
  235.                                     myStmt.close();
  236.                                 }
  238.                                 if (myConn != null) {
  239.                                     myConn.close();
  240.                                 }
  241.                             }
  242.                             break;
  244.                         case 3:
  245.                             try {
  246.                                 // Update Book Author
  247.                                 System.out.print("Enter New Author: ");
  248.                                 String author = input.next();
  250.                                 // 1. Get a connection to database
  251.                                 myConn = DriverManager.getConnection(url, user, password);
  253.                                 // 2. Create a statement
  254.                                 String sql1 = "UPDATE books SET author = ? WHERE id = ?";
  255.                                 myStmt = myConn.prepareStatement(sql1);
  257.                                 // Set parameter values
  258.                                 myStmt.setString(1, author);
  259.                                 myStmt.setInt(2, id);
  261.                                 // 3. Execute SQL query
  262.                                 myStmt.execute();
  264.                                 System.out.println("Autor updated.");
  265.                                 printAllFromTable(myStmt);
  267.                             } catch (Exception exc) {
  268.                                 exc.printStackTrace();
  270.                             } finally {
  271.                                 if (myStmt != null) {
  272.                                     myStmt.close();
  273.                                 }
  275.                                 if (myConn != null) {
  276.                                     myConn.close();
  277.                                 }
  278.                             }
  279.                             break;
  281.                         case 4:
  282.                             try {
  283.                                 // Update Book Quantity
  284.                                 System.out.print("Enter New Quantity: ");
  285.                                 int qty = input.nextInt();
  287.                                 // 1. Get a connection to database
  288.                                 myConn = DriverManager.getConnection(url, user, password);
  290.                                 // 2. Create a statement
  291.                                 String sql1 = "UPDATE books SET qty = ? WHERE id = ?";
  292.                                 myStmt = myConn.prepareStatement(sql1);
  294.                                 // Set parameter values
  295.                                 myStmt.setInt(1, qty);
  296.                                 myStmt.setInt(2, id);
  298.                                 // 3. Execute SQL query
  299.                                 myStmt.execute();
  301.                                 System.out.println("Quantity updated.");
  302.                                 printAllFromTable(myStmt);
  304.                             } catch (Exception exc) {
  305.                                 exc.printStackTrace();
  307.                             } finally {
  308.                                 if (myStmt != null) {
  309.                                     myStmt.close();
  310.                                 }
  312.                                 if (myConn != null) {
  313.                                     myConn.close();
  314.                                 }
  315.                             }
  316.                             break;
  318.                         case 5:
  319.                             break;
  321.                         default:
  322.                             System.out.println("Invalid Entry");
  323.                         }
  325.                     } while (menu != 5);
  327.                 } catch (Exception exc) {
  328.                     exc.printStackTrace();
  330.                 } finally {
  331.                     if (myStmt != null) {
  332.                         myStmt.close();
  333.                     }
  335.                     if (myConn != null) {
  336.                         myConn.close();
  337.                     }
  338.                 }
  340.                 break;
  342.             case 3:
  343.                 // Delete a book from the database
  344.                 System.out.println("3. Delete book\n-----------------------------");
  345.                 try {
  346.                     // Search
  347.                     System.out.print("Enter Book ID to delete: ");
  348.                     int searchId = input.nextInt();
  349.                     int id = searchId;
  350.                     // 1. Get a connection to database
  351.                     myConn = DriverManager.getConnection(url, user, password);
  353.                     // 2. Create a statement
  354.                     String sql = "DELETE FROM books WHERE id = ?";
  355.                     myStmt = myConn.prepareStatement(sql);
  357.                     // Set parameter values
  358.                     myStmt.setInt(1, id);
  360.                     // 3. Execute SQL query
  361.                     myStmt.executeUpdate();
  362.                     System.out.println("Delete complete.\n");
  364. //                  printAllFromTable(myStmt);
  366.                 } catch (Exception exc) {
  367.                     exc.printStackTrace();
  369.                 } finally {
  370.                     if (myStmt != null) {
  371.                         myStmt.close();
  372.                     }
  374.                     if (myConn != null) {
  375.                         myConn.close();
  376.                     }
  377.                 }
  379.                 break;
  381.             case 4:
  382.                 // Search for a book in the database
  383.                 System.out.println("4. Search books\n-----------------------------");
  384.                 System.out.println();
  386.                 do {
  387.                     // Sub menu for searching by ID, title or author
  388.                     System.out.println("1. Enter ID");
  389.                     System.out.println("2. Enter Title");
  390.                     System.out.println("3. Enter Author");
  391.                     System.out.println("4. Main menu");
  392.                     System.out.print("\nPlease enter your choice: ");
  393.                     menu = input.nextInt();
  394.                     System.out.println();
  395.                     switch (menu) {
  397.                     case 1:
  398.                         try {
  399.                             // Search by book id
  400.                             System.out.print("Enter Book ID: ");
  401.                             int searchId = input.nextInt();
  402.                             int id = searchId;
  403.                             ResultSet results;
  405.                             // 1. Get a connection to database
  406.                             myConn = DriverManager.getConnection(url, user, password);
  408.                             // 2. Create a statement
  409.                             String sql = "SELECT * FROM books WHERE id = ?";
  410.                             myStmt = myConn.prepareStatement(sql);
  412.                             // Set parameter values
  413.                             myStmt.setInt(1, id);
  415.                             // 3. Execute SQL query
  416.                             results = myStmt.executeQuery();
  418.                             // Loop over the results, printing them all.
  419.                             while (results.next()) {
  420.                                 System.out.println(results.getInt("id") + ", " + results.getString("title") + ", "
  421.                                         + results.getString("author") + ", " + results.getInt("qty"));
  422.                             }
  424.                         } catch (Exception exc) {
  425.                             exc.printStackTrace();
  427.                         } finally {
  428.                             if (myStmt != null) {
  429.                                 myStmt.close();
  430.                             }
  432.                             if (myConn != null) {
  433.                                 myConn.close();
  434.                             }
  435.                         }
  436.                         break;
  438.                     case 2:
  439.                         try {
  440.                             // Search by book title
  441.                             System.out.print("Enter Book Title: ");
  442.                             String searchTitle = input.next();
  443.                             String title = searchTitle;
  444.                             ResultSet results;
  446.                             // 1. Get a connection to database
  447.                             myConn = DriverManager.getConnection(url, user, password);
  449.                             // 2. Create a statement
  450.                             String sql = "SELECT * FROM books WHERE title = ?";
  451.                             myStmt = myConn.prepareStatement(sql);
  453.                             // Set parameter values
  454.                             myStmt.setString(1, title);
  456.                             // 3. Execute SQL query
  457.                             results = myStmt.executeQuery();
  459.                             // Loop over the results, printing them all.
  460.                             while (results.next()) {
  461.                                 System.out.println(results.getInt("id") + ", " + results.getString("title") + ", "
  462.                                         + results.getString("author") + ", " + results.getInt("qty"));
  463.                             }
  465.                         } catch (Exception exc) {
  466.                             exc.printStackTrace();
  468.                         } finally {
  469.                             if (myStmt != null) {
  470.                                 myStmt.close();
  471.                             }
  473.                             if (myConn != null) {
  474.                                 myConn.close();
  475.                             }
  476.                         }
  477.                         break;
  479.                     case 3:
  480.                         try {
  481.                             // Search by book Author
  482.                             System.out.print("Enter Author: ");
  483.                             String searchAuthor = input.next();
  484.                             String title = searchAuthor;
  485.                             ResultSet results;
  487.                             // 1. Get a connection to database
  488.                             myConn = DriverManager.getConnection(url, user, password);
  490.                             // 2. Create a statement
  491.                             String sql = "SELECT * FROM books WHERE author = ?";
  492.                             myStmt = myConn.prepareStatement(sql);
  494.                             // Set parameter values
  495.                             myStmt.setString(1, title);
  497.                             // 3. Execute SQL query
  498.                             results = myStmt.executeQuery();
  500.                             // Loop over the results, printing them all.
  501.                             while (results.next()) {
  502.                                 System.out.println(results.getInt("id") + ", " + results.getString("title") + ", "
  503.                                         + results.getString("author") + ", " + results.getInt("qty"));
  504.                             }
  506.                         } catch (Exception exc) {
  507.                             exc.printStackTrace();
  509.                         } finally {
  510.                             if (myStmt != null) {
  511.                                 myStmt.close();
  512.                             }
  514.                             if (myConn != null) {
  515.                                 myConn.close();
  516.                             }
  517.                         }
  518.                         break;
  520.                     case 4:
  521.                         break;
  523.                     default:
  524.                         System.out.println("Invalid Entry");
  525.                     }
  527.                 } while (menu != 4);
  528.                 break;
  530.             case 5:
  531.                 // Exits the program
  532.                 System.out.println("Exiting...");
  533.                 quit = true;
  534.                 break;
  536.             default:
  537.                 System.out.println("Invalid Entry");
  538.             }
  539.         } while (!quit);
  541.         if (input != null) {
  542.             input.close();
  543.         }
  545.     }
  547.     /**
  548.      * Method printing all values in all rows. Takes a statement to try to avoid
  549.      * spreading DB access too far.
  550.      * 
  551.      * @param a statement on an existing connection
  552.      * @throws SQLException
  553.      */
  555.     public static void printAllFromTable(Statement statement) throws SQLException {
  557.         ResultSet results = statement.executeQuery("SELECT id, title, author, qty FROM books");
  558.         while (results.next()) {
  559.             System.out.println(results.getInt("id") + ", " + results.getString("title") + ", "
  560.                     + results.getString("author") + ", " + results.getInt("qty"));
  561.         }
  562.     }
  564. }
Javamysqljava.util.scanner

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