將結果集中的值寫入文本文件（.txt 文件）

Question

請幫助我處理以下代碼，因為我想將結果集中的值寫入 txt 文件

代碼

while (rs.next()){
    FileWriter fstream = new FileWriter(file);
    BufferedWriter out = new BufferedWriter(fstream);

    out.write(Integer.toString(rs.getInt("SBL_PRODUCT_ID")) + ", ");
    out.write(Integer.toString(rs.getInt("SBL_TARIFF_ID")) + ", ");
    out.write(rs.getString("PRODUCT_DESCRIPTION") + ", ");
    out.write(rs.getString("SERVICE_TYPE") + ", ");
    out.write(Integer.toString(rs.getInt("MARKET_CLASS")) + ", ");
    out.write(rs.getString("ENTITY_TYPE") + ", ");
    out.newLine();
    /*out.write(System.getProperty("line.separator"));*/

    System.out.println("Completed writing into text file");
    out.close();
}

txt 文件中的必需輸出

4087, 98, POSTE SIM, Deal [SoHo Flat Tariff Recurring Charge, Prepaid], /service/telco/SIM, 101, DEAL

4087, 99, POSTE SIM, Deal [SoHo Flat Tariff Recurring Charge, Prepaid], /service/telco/SIM, 101, DEAL

4087, 100, POSTE SIM, Deal [SoHo Flat Tariff Recurring Charge, Prepaid], /service/telco/SIM, 101, DEAL

4087, 101, POSTE SIM, Deal [SoHo Flat Tariff Recurring Charge, Prepaid], /service/telco/SIM, 101, DEAL

我得到的當前輸出只是一行，也是結果集中的最后一個值，即下面

電流輸出

4087, 101, POSTE SIM, Deal [SoHo Flat Tariff Recurring Charge, Prepaid], /service/telco/SIM, 101, DEAL

請幫我解決這個問題:(

Answer 1

打開文件一次，將內容寫入其中，然后在寫入所有內容后關閉，例如

try (BufferedWriter out = new BufferedWriter(new FileWriter(file))) {
    while (rs.next()) {
        out.write(Integer.toString(rs.getInt("SBL_PRODUCT_ID")) + ", ");
        out.write(Integer.toString(rs.getInt("SBL_TARIFF_ID")) + ", ");
        out.write(rs.getString("PRODUCT_DESCRIPTION") + ", ");
        out.write(rs.getString("SERVICE_TYPE") + ", ");
        out.write(Integer.toString(rs.getInt("MARKET_CLASS")) + ", ");
        out.write(rs.getString("ENTITY_TYPE") + ", ");
        out.newLine();
    }
    System.out.println("Completed writing into text file");
}

查看try-with-resources 聲明以了解更多詳細信息

Answer 2

每次創建文件編寫器時，都會覆蓋該文件。 將其更改為：

FileWriter fstream = new FileWriter(file);
BufferedWriter out = new BufferedWriter(fstream);
while (rs.next()) {            
        out.write(Integer.toString(rs.getInt("SBL_PRODUCT_ID")) + ", ");
        out.write(Integer.toString(rs.getInt("SBL_TARIFF_ID")) + ", ");
        out.write(rs.getString("PRODUCT_DESCRIPTION") + ", ");
        out.write(rs.getString("SERVICE_TYPE") + ", ");
        out.write(Integer.toString(rs.getInt("MARKET_CLASS")) + ", ");
        out.write(rs.getString("ENTITY_TYPE") + ", ");
        out.newLine();
        /*out.write(System.getProperty("line.separator"));*/
}
System.out.println("Completed writing into text file");
out.close();

或者，您可以在FileWriter設置append標志：

FileWriter fstream = new FileWriter(file, true);

雖然這不如只打開一次文件那么有效。

Answer 3

來自 GitHub： https : //github.com/OhadR/ohadr.common/blob/master/src/main/java/com/ohadr/common/utils/resultset/ResultSetConverters.java

public static void writeResultSetToWriter(ResultSet resultSet, PrintWriter writer) throws SQLException
{
ResultSetMetaData metadata = resultSet.getMetaData();
int numColumns = metadata.getColumnCount();
int numRows = 0;

while(resultSet.next())             //iterate rows
{
    ++numRows;
    JSONObject obj = new JSONObject();      //extends HashMap
    for (int i = 1; i <= numColumns; ++i)           //iterate columns
    {
        String column_name = metadata.getColumnName(i);
        obj.put(column_name, resultSet.getObject(column_name));
    }
    writer.println(obj.toJSONString());

    if(numRows % 1000 == 0)
        writer.flush();
}

}