Java：用Prepared Statements在MySQL數據庫中插入批處理數據

Question

我創建了一個自定義函數來在我的MySQL數據庫中插入數據。這些函數首先根據給定的輸入創建一個查詢。該查詢將看起來像INSERT INTO tableName (columnName1, ..., columnNamei) VALUES (?, ..., ?), ..., (?, ...,?)。之後，需要製作PreparedStatement，其中包含真實值。這些需要添加到批處理中，因爲我想一次添加多行（如此處所示：Java: Insert multiple rows into MySQL with PreparedStatement）。下面是代碼：

insertData（）函數

public static void insertData(String table, List<HashMap<String, Object>> list) throws SQLException { 

    //Create query: make sure all of the rows in the table get the same amount of values passed 
    //Prepare colnames string 
    String colNamesParsed = ""; 
    int counter = 1; 

    //Iterate over only the first hashmap of the list (THATS WHY ALL THE ROWS NEED TO HAVE THE SAME AMOUNT OF VALUES PASSED) 
    for (String colName : list.get(0).keySet()) { 

     //Check if it is the last col name 
     if (counter != list.get(0).keySet().size()) { 
      colNamesParsed = colNamesParsed + colName+", "; 
     } 
     else { 
      colNamesParsed = colNamesParsed + colName; 
     } 

     counter++; 
    } 

    //Now create the place holder for the query variables 
    String queryVariablesPlaceholder = ""; 
    int rowSize = 0; 
    for (HashMap<String, Object> row : list) { 

     //This part is to check if all row sizes are equal 
     if (rowSize == 0) { 
      rowSize = row.values().size(); 
     } 
     else { 
      //Check if the rowsize is equal for all rows 
      if (row.values().size() != rowSize) { 
       System.out.println("The rows of the arrays are from a different size"); 
       return; 
      } 
     } 

     String queryVariablesRow = "(?, "; 
     for (int j = 1; j < (row.values().size()-1); j++) { 
      queryVariablesRow = queryVariablesRow+"?, "; 
     } 
     queryVariablesRow = queryVariablesRow+"?)"; 

     //Make sure the query does not start with a comma 
     if (queryVariablesPlaceholder.equals("")) { 
      queryVariablesPlaceholder = queryVariablesRow; 
     } 
     else { 
      queryVariablesPlaceholder = queryVariablesPlaceholder+", "+queryVariablesRow; 
     } 
    } 

    //The MySQL query needs to be built now 
    String query = "INSERT INTO "+table+" ("+colNamesParsed+") VALUES "+queryVariablesPlaceholder+";"; 
    System.out.println(query); 

    //Init prepared statement 
    PreparedStatement statement = con.prepareStatement(query); 

    for (HashMap<String, Object> map : list) { 

     int varCounter = 1; 
     //Iterate over all values that need to be inserted 
     for (Object object : map.values()) { 

      if (object instanceof Integer) { 
       statement.setInt(varCounter, Integer.parseInt(object.toString())); 
      } 
      else if (object instanceof String) { 
       statement.setString(varCounter, object.toString()); 
      } 
      else if (object instanceof Timestamp) { 
       statement.setTimestamp(varCounter, parseStringToTimestamp(object.toString())); 
      } 
      else if (object instanceof Double) { 
       statement.setDouble(varCounter, Double.parseDouble(object.toString())); 
      } 
      System.out.println(varCounter); 
      varCounter++; 
     } 

     //Add row to the batch 
     try { 
      statement.addBatch(); 
     } 
     catch (SQLException e) { 
      e.printStackTrace(); 
     } 

    } 
    //Execute the query, which is in fact the batch 
    statement.executeBatch(); 
} 

當我想在數據庫中插入一些數據，我執行下面的代碼：

功能部分

List<HashMap<String, Object>> list = new ArrayList<>(); 
    for (Object object : listOfObjects) { 
     HashMap<String, Object> map = new HashMap<>(); 
     map.put("columnName1", object.getSomeValue()); 
     /....../ 
     map.put("columnName2", object.getSomeOtherValue()); 

     list.add(map); 
    } 

    Functions.insertData("tableName", list); 

創建動態查詢似乎完美。但是，我無法使statement.addBatch()正常工作。它不斷給我下面的錯誤：

java.sql.SQLException: No value specified for parameter 9 

我不明白這一點，因爲我只有8個參數在批處理的各單位通過。我的目標表有9列，所以我試圖爲該列添加一個值，但它說：No value specified for parameter 10，所以它好像不關閉「批處理單元」或其他東西。

我在這裏錯過了什麼？

任何幫助，非常感謝！

Answer 1

這

INSERT INTO tableName (columnName1, ..., columnNamei) VALUES (?, ..., ?), ..., (?, ...,?) 

是不是標準的SQL語法。 如果你使用這個JDBC，將爲每個「？」指定一個參數在你的查詢中。

用途：

INSERT INTO表名（columnName1，...，columnNamei）VALUES

和每個語句添加到批處理（，...？）。