从结果集 java 中获取日期时间

Question

I have two columns which store DateTime values in a MySql database,

When I try to get them from a ResultSet in Java there is no option: getDateTime()

Should I use getDate() or wouldn't that work?

Thanks in advance

Answer 1

使用getDate()只返回一个Date ，所以在你的情况下，如果你想要日期和时间，请使用getTimestamp(String columnLabel) - 这应该有效，也可以用数据库中的实际列名替换String columnLabel 。

Answer 2

您可以使用ResultSet.getTimeStamp()

Answer 3

Prefer timestamp over datetime in MySQL

First, if the datetime in your database is to represent a point in time, use the timestamp datatype in MySQL for that, not datetime . A datetime is open for interpretation into any time zone the reader or the program reading it happens to use. This can lead to errors that are hard to debug. The timestamp datatype behaves differently in various RDBMSs. In MySQL it makes sure that dates and times are in UTC, thus excluding faulty interpretation into any other time zone. It's safer. If the dates and times are a little harder for users in your own time zone to read in the database, it's worth it.

java.time

    PreparedStatement ps = yourDatabaseConnection.prepareStatement("select your_datetime_col from your_table;");
    try (ResultSet rs = ps.executeQuery()) {
        while (rs.next()) {
            OffsetDateTime dateTime = rs.getObject("your_datetime_col", OffsetDateTime.class);
            // do something with dateTime
        }
    }

Use ResultSet.getObject() for retrieving date and time from the database into a type from java.time, the modern Java date and time API. The classes java.sql.Timestamp , java.sql.Date and java.util.Date mentioned or implied in the question and the other answers are all poorly designed and long outdated, so I recommend the modern API instead. It requires a JDBC 4.2 compliant driver. Most of us have that, and one has been out for MySQL for very many years. SO I expect that you are fine.

If you cannot change the datatype in MySQL, use LocalDateTime in Java for retrieving values from your datatime column. It goes in the same way as in the code above.

To answer your concrete question

Should I use getDate() or wouldn't that work?

No it would not. getDate() gives you a java.sql.Date holding only the date part from the database, the time of day part will be missing. As I said, java.sql.Date is also poorly designed — a true hack on top of the already poorly designed java.util.Date — so you shouldn't want that anyway.

Links

• Java Best Practice for Date Manipulation/Storage for Geographically Diverse Users
• My answer to Getting the date from a ResultSet for use with java.time classes
• Oracle tutorial: Date Time explaining how to use java.time.

Answer 4

Or with a typecast from date to string:

resultSet.getDate(1).toString());

will return:

2014-02-18

DB field data: "2014-02-18 00:00:00.000"

Answer 5

Converting java.sql.Timestamp to java.util.Date .

java.util.Date date = rs.getDate(index_position); // O/P: DD:MM:YYYY

java.sql.Timestamp timestamp = rs.getTimestamp(index_position); // O/P: DD:MM:YYYY HH:mm:ss
java.util.Date date = new java.util.Date(timestamp.getTime());

If you timestamp to date and convert it to java.sql.Timestamp then it results to DD:MM:YYYY 00:00:00 as the date will not cover time. So, it picks default as 00:00:00 .

SQL TimeStamp  : 30.12.2020 13.40.50
Java TimeStamp : 30.12.2020 13.40.50

SQL TimeStamp  : 30.12.2020 13.40.50
Java Date      : 30.12.2020 00.00.00
Java TimeStamp : 30.12.2020 00.00.00

Example to get records based on ResultSetMetaData for CSV Report:

public static void getTestTable(Connection con) throws SQLException {
    String sql = "select ID, INSERTDATE, TO_CHAR(INSERTTIME,'DD.MM.YYYY HH24:MI:SS') as String_Time, INSERTTIME, MSG from TEST_TABLE group by ID, INSERTDATE, INSERTTIME, MSG";
    Statement stmt = con.createStatement();
    ResultSet rs = stmt.executeQuery(sql);
    if (rs != null) {
        ResultSetMetaData resultSetMetaData = rs.getMetaData();
        int noOfColumns = resultSetMetaData.getColumnCount(); // For iteration
        System.out.println("No of Cloumns Query Returns: "+ noOfColumns);
        HashMap<String, ArrayList<?>> matrixTable = getMatrixMetadata(resultSetMetaData);
        System.out.println("MatrixTable: "+matrixTable);
        ArrayList<String> dataTypeList = (ArrayList<String>) matrixTable.get("ColumnTypeName");
        int rowCount = 0;
        while (rs.next()) { // CSV Report
            for (int columnIndex = 1; columnIndex <= noOfColumns; columnIndex++) {
                // int id = rs.getInt("ID");
                String value = getMatrixValue(rs, dataTypeList, columnIndex);
                System.out.print(value);
                if (columnIndex < noOfColumns) {
                    System.out.print(",");
                }
            }
            System.out.println();
            rowCount++;
        }
        System.out.println("Result FetchSize(Total Coloumns):"+rs.getFetchSize()+" = Rows*Coloums:["+rowCount+"*"+noOfColumns+"]"); 
    }
}
static HashMap<String, ArrayList<?>> getMatrixMetadata(ResultSetMetaData meta) throws SQLException {
    int columnsCount = meta.getColumnCount();
    ArrayList<String> columnList = new ArrayList<String>();
    ArrayList<String> dataTypeNameList = new ArrayList<String>();
    ArrayList<Integer> dataTypeIdList = new ArrayList<Integer>();
    HashMap<String, ArrayList<?>> returnHashMap = new HashMap<String, ArrayList<?>>();
    for (int i = 1; i <= columnsCount; i++) {
        columnList.add(meta.getColumnName(i));
        dataTypeIdList.add(Integer.valueOf(meta.getColumnType(i)));
        dataTypeNameList.add(meta.getColumnTypeName(i));
    }
    returnHashMap.put("ColumnName", columnList);
    returnHashMap.put("ColumnTypeId", dataTypeIdList);
    returnHashMap.put("ColumnTypeName", dataTypeNameList);
    return returnHashMap;
}
static DecimalFormat DECIMAL_FORMAT = (DecimalFormat) NumberFormat.getInstance(Locale.ENGLISH);
static { // https://docs.oracle.com/javase/7/docs/api/java/text/DecimalFormat.html
    DECIMAL_FORMAT.applyPattern("######.###"); // "#,#00.0#" → 1,234.56 
}
public static String getMatrixValue(ResultSet rs, ArrayList<String> dataTypeNameList, int pos) throws SQLException {
    String retval;
    String columnTypeName = dataTypeNameList.get(pos - 1);
    //int type = dataTypeIdList.get(pos - 1);
    //if (type == Types.DECIMAL || type == Types.DOUBLE || type == Types.FLOAT || type == Types.NUMERIC || type == Types.REAL) {
    if (columnTypeName.equalsIgnoreCase("NUMBER")) {
        double doubleValue = rs.getDouble(pos);
        if (rs.wasNull()) {
            retval = null;
        } else {
            retval = "[N]"+DECIMAL_FORMAT.format(doubleValue);
        }
    } else if (columnTypeName.equalsIgnoreCase("DATE")) {
        java.util.Date date = rs.getDate(pos);
        if (rs.wasNull()) { // Checks last column read had a value of SQL NULL.
            retval = null;
        } else {
            retval = "[D]"+formatDate(date, "dd.MM.yy");
        }
    } else if (columnTypeName.equalsIgnoreCase("TIMESTAMP")) {
        java.sql.Timestamp timestamp = rs.getTimestamp(pos);
        if (rs.wasNull()) {
            retval = null;
        } else {
            java.util.Date date = new java.util.Date(timestamp.getTime());
            retval = "[T]"+formatDate(date, "dd.MM.yyyy HH:mm");
        }
    } else { // VARCHAR2
        retval = "[S]"+rs.getString(pos);
    }
    return retval;
}
public static String formatDate(Date aDate, String formatStr) {
    DateFormat dateFormat = new SimpleDateFormat( formatStr );
    //dateFormat.setCalendar(Calendar.getInstance(TimeZone.getTimeZone("IST")));
    return dateFormat.format(aDate);
}

No of Cloumns Query Returns: 5
MatrixTable: {ColumnName=[ID, INSERTDATE, STRING_TIME, INSERTTIME, MSG], ColumnTypeId=[2, 93, 12, 93, 12], ColumnTypeName=[NUMBER, DATE, VARCHAR2, TIMESTAMP, VARCHAR2]}
[N]1,[D]30.12.20,[S]30.12.2020 00:40:50,[T]30.12.2020 00:40,[S]Insert1
[N]2,[D]30.12.20,[S]30.12.2020 13:40:50,[T]30.12.2020 13:40,[S]Insert2
Result FetchSize(Total Coloumns):10 = Rows*Coloums:[2*5]

SQL queries involved are for Table creation and multi record insertion: ^{Oracle Multi insert}

CREATE TABLE SCHEMA7.TEST_TABLE ( "ID" NUMBER, "INSERTDATE" DATE, "INSERTTIME" TIMESTAMP (6), "MSG" VARCHAR2(120 BYTE) );

INSERT INTO SCHEMA7.TEST_TABLE  (ID, INSERTDATE, INSERTTIME, MSG) VALUES ('1', TO_DATE('30-DEC-2020', 'DD-MON-RR'), TO_TIMESTAMP('30-DEC-2020 12.40.50.00 AM', 'DD-MON-RR HH.MI.SS.FF AM'), 'Insert1');
INSERT INTO SCHEMA7.TEST_TABLE  (ID, INSERTDATE, INSERTTIME, MSG) VALUES ('2', TO_DATE('30.12.2020', 'DD.MM.YYYY'), TO_TIMESTAMP('30.12.2020 13.40.50','dd.mm.yyyy hh24.mi.ss'), 'Insert2');