使用唯一列向表添加行：获取现有ID值和新创建的值

时间：2014-11-11 05:36:58

标签： java mysql jdbc

我有以下表结构

  1. mail_contacts(id,mail_id);//stores mail id, id is primary key
                                  mail_id is unique key
  2. inv_table(mid,aid,add_date);//mapped mail id with user id. mid is 
                                   mail_contacts id and aid is userid
                                   (mid,aid) is primary key

我在插入后在mail_contacts存储了多个邮件ID我正在获取其插入的ID并在inv_table的帮助下存储它。 如果mail_id中没有任何mail_contacts存储在mail_id，那么它正常运行。 但如果mail_contacts存储在mail_id中，则插入将被终止。

我想要的如果mail_contacts存储在id中，那么它应该获取其inv_table来存储 PreparedStatement ps = null; PreparedStatement ps1 = null; ResultSet rs = null, res = null; Connection con = null; String status = "success"; ArrayList ar = null; Invitation invi = null; int i = 0; public String insert(List<MailidInvitation> invitationList, Long aid) { con = ConnectionFactory.getConnection(); try { ps = con.prepareStatement("insert into mail_contacts(mail_id)" + " values(?)", Statement.RETURN_GENERATED_KEYS); for (MailidInvitation a : invitationList) { ps.setString(1, a.getMailId()); ps.addBatch(); } ps.executeBatch(); ResultSet keys = ps.getGeneratedKeys(); while (keys.next()) { long id = keys.getLong(1); invitationList.get(i).setId(id); System.out.println("generated id is " + id); i++; } ps1 = con.prepareStatement("insert into inv_table(mid,aid)" + " values(?,?)"); for (MailidInvitation a : invitationList) { ps1.setLong(1, a.getId()); ps1.setLong(2, aid); ps1.addBatch(); } ps1.executeBatch(); } catch (SQLException e) { status = "failure"; System.out.println("SQLException1 " + e); } finally { try { con.close(); } catch (SQLException e) { System.out.println("SQLException2 " + e); } } System.out.println("Status is " + status); return status; } 。

我正在尝试

{{1}}

怎么做？

解决此类问题的最佳方法是什么

我正在使用mysql数据库

2 个答案:

答案 0 :(得分：1)

第一种方法在处理批处理INSERT时不会对JDBC驱动程序的行为做出任何假设。它通过

避免了潜在的INSERT错误
  • 在表中查询当前数据集中的任何现有mail_id值
  • 记下了确实存在的id值的相应mail_id值，
  • 插入不存在的mail_id值，并检索其（新）id值，然后
  • 将行插入另一个表（inv_table）。
try (Connection dbConn = DriverManager.getConnection(myConnectionString, "root", "usbw")) {
    dbConn.setAutoCommit(false);

    // test data and setup
    Long aid = 123L;
    List<MailidInvitation> invitationList = new ArrayList<MailidInvitation>();
    invitationList.add(new MailidInvitation(13L));
    invitationList.add(new MailidInvitation(11L));
    invitationList.add(new MailidInvitation(12L));
    // remove stuff from previous test run
    try (Statement s = dbConn.createStatement()) {
        s.executeUpdate("DELETE FROM mail_contacts WHERE mail_id IN (11,13)");
    }
    try (PreparedStatement ps = dbConn.prepareStatement(
            "DELETE FROM inv_table WHERE aid=?")) {
        ps.setLong(1, aid);
        ps.executeUpdate();
    }

    // real code starts here
    //
    // create a Map to hold `mail_id` and their corresponding `id` values 
    Map<Long, Long> mailIdMap = new TreeMap<Long, Long>();
    for (MailidInvitation a : invitationList) {
        // mail_id, id (id is null for now)
        mailIdMap.put(a.getId(), null);
    }

    // build an SQL statement to retrieve any existing values
    StringBuilder sb = new StringBuilder(
            "SELECT id, mail_id " +
            "FROM mail_contacts " +
            "WHERE mail_id IN (");
    int n = 0;
    for (Map.Entry<Long, Long> entry : mailIdMap.entrySet()) {
        if (n++ > 0) sb.append(',');
        sb.append(entry.getKey());
    }
    sb.append(')');
    String sql = sb.toString();

    // run the query and save the results (if any) to the Map
    try (Statement s = dbConn.createStatement()) {
        // <demo>
        System.out.println(sql);
        // </demo>
        try (ResultSet rs = s.executeQuery(sql)) {
            while (rs.next()) {
                mailIdMap.put(rs.getLong("mail_id"), rs.getLong("id"));
            }
        }
    }

    // <demo>
    System.out.println();
    System.out.println("mailIdMap now contains:");
    // </demo>

    // build a list of the `mail_id` values to INSERT (where id == null)
    //     ... and print the existing mailIdMap values for demo purposes
    List<Long> mailIdsToInsert = new ArrayList<Long>();
    for (Map.Entry<Long, Long> entry : mailIdMap.entrySet()) {
        String idValue = "";  // <demo />
        if (entry.getValue() == null) {
            mailIdsToInsert.add(entry.getKey());
            // <demo>
            idValue = "null";  
        } else {
            idValue = entry.getValue().toString();
            // </demo>
        }
        // <demo>
        System.out.println(String.format(
                "    %d - %s", 
                entry.getKey(),
                idValue));
        // </demo>
    }

    // batch insert `mail_id` values that don't already exist
    try (PreparedStatement ps = dbConn.prepareStatement(
            "INSERT INTO mail_contacts (mail_id) VALUES (?)", 
            PreparedStatement.RETURN_GENERATED_KEYS)) {
        for (Long mid : mailIdsToInsert) {
            ps.setLong(1, mid);
            ps.addBatch();
        }
        ps.executeBatch();
        // get generated keys and insert them into the Map
        try (ResultSet rs = ps.getGeneratedKeys()) {
            n = 0;
            while (rs.next()) {
                mailIdMap.put(mailIdsToInsert.get(n++), rs.getLong(1));
            }
        }
    }

    // <demo>
    System.out.println();
    System.out.println("After INSERT INTO mail_contacts, mailIdMap now contains:");
    for (Map.Entry<Long, Long> entry : mailIdMap.entrySet()) {
        System.out.println(String.format(
                "    %d - %s", 
                entry.getKey(),
                entry.getValue()));
    }
    // </demo>

    // now insert the `inv_table` rows
    try (PreparedStatement ps = dbConn.prepareStatement(
            "INSERT INTO inv_table (mid, aid) VALUES (?,?)")) {
        ps.setLong(2, aid);
        for (MailidInvitation a : invitationList) {
            ps.setLong(1, mailIdMap.get(a.getId()));
            ps.addBatch();
        }
        ps.executeBatch();
    }
    dbConn.commit();
}

生成的控制台输出如下所示：

SELECT id, mail_id FROM mail_contacts WHERE mail_id IN (11,12,13)

mailIdMap now contains:
    11 - null
    12 - 1
    13 - null

After INSERT INTO mail_contacts, mailIdMap now contains:
    11 - 15
    12 - 1
    13 - 16

如果批处理中的一个或多个语句失败，某些JDBC驱动程序允许批处理继续。例如，在MySQL Connector / J中，选项为continueBatchOnError，默认为true。在这些情况下，另一种方法是尝试并插入所有mail_id值并检查批处理返回的更新计数。成功的INSERT将返回UpdateCount为1，而由于现有mail_id而失败的INSERT将返回EXECUTE_FAILED（ - 3）。然后我们可以通过id检索成功INSERT的（新）.getGeneratedKeys()值，然后继续构建SELECT语句以返回并检索id的{​​{1}}值已经存在的条目。

所以像这样的代码

mail_id

将产生如下控制台输出：

// create a Map to hold `mail_id` and their corresponding `id` values 
Map<Long, Long> mailIdMap = new TreeMap<Long, Long>();
for (MailidInvitation a : invitationList) {
    // mail_id, id (id is null for now)
    mailIdMap.put(a.getId(), null);
}

// try INSERTing all `mail_id` values
try (PreparedStatement ps = dbConn.prepareStatement(
        "INSERT INTO mail_contacts (mail_id) VALUES (?)", 
        PreparedStatement.RETURN_GENERATED_KEYS)) {
    for (Long mid : mailIdMap.keySet()) {
        ps.setLong(1, mid);
        ps.addBatch();
    }
    int[] updateCounts = null;
    try {
        updateCounts = ps.executeBatch();
    } catch (BatchUpdateException bue) {
        updateCounts = bue.getUpdateCounts();
    }
    // get generated keys and insert them into the Map
    try (ResultSet rs = ps.getGeneratedKeys()) {
        int i = 0;
        for (Long mid : mailIdMap.keySet()) {
            if (updateCounts[i++] == 1) {
                rs.next();
                mailIdMap.put(mid, rs.getLong(1));
            }
        }
    }
}

// <demo>
System.out.println("mailIdMap now contains:");
// </demo>

// build a SELECT statement to get the `id` values for `mail_id`s that already existed
//     ... and print the existing mailIdMap values for demo purposes
StringBuilder sb = new StringBuilder(
        "SELECT id, mail_id " +
        "FROM mail_contacts " +
        "WHERE mail_id IN (");
int n = 0;
for (Map.Entry<Long, Long> entry : mailIdMap.entrySet()) {
    String idValue = "";  // <demo />
    if (entry.getValue() == null) {
        if (n++ > 0) sb.append(',');
        sb.append(entry.getKey());
        // <demo>
        idValue = "null";  
    } else {
        idValue = entry.getValue().toString();
        // </demo>
    }
    // <demo>
    System.out.println(String.format(
            "    %d - %s", 
            entry.getKey(),
            idValue));
    // </demo>
}
sb.append(')');
String sql = sb.toString();

// <demo>
System.out.println();
System.out.println(sql);
// </demo>

其余过程与以前相同：

  • 填写剩余的mailIdMap now contains: 11 - 17 12 - null 13 - 19 SELECT id, mail_id FROM mail_contacts WHERE mail_id IN (12) 条目和
  • 使用mailIdMap中的id值处理另一个表上的INSERT。

答案 1 :(得分：0)

如果我理解得很好，那么问题在于第一部分：insert into mail_contacts(mail_id) values(?)因重复键而引发异常。

我会通过维护数据库内容的本地副本来解决这个问题：

  • 首次调用该方法：获取mail_contacts的所有内容并将其存储在Set（existingMailIds，类字段）
  • 在执行第一部分时，请检查列表以查看mailId是否存在，如果存在，请不要addBatch。
  • 使用新插入的existingMailIds更新insert into inv_table(mid,aid) values(?,?)
  • 执行第2步：{{1}}

类似的东西。

相关问题
最新问题