我有以下表格结构
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
插入后，我将多个邮件id存储在
mail_contacts中，我将获取其插入的id，并借助inv_table将其存储。如果任何
mail_id未存储在mail_contacts中，则它工作正常。但如果
mail_id存储在mail_contacts中，则插入终止。我想要的是如果
mail_id存储在mail_contacts中，那么它应该取它的id存储在inv_table。我在努力
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;
}
怎么做？
解决这种问题的最好办法是什么
我正在使用mysql数据库
最佳答案
第一种方法在处理批插入时不假设JDBC驱动程序的行为。它避免了潜在的插入错误
在当前数据集中查询任何现有的mail_id值，
注意确实存在的那些id值对应的mail_id值，
插入不存在的mail_id值，并检索它们的（新）id值，然后
在另一个表中插入行（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();
}
结果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
某些JDBC驱动程序允许在批处理中的一个或多个语句失败时继续批处理。例如，在MySQL Connector/J中，选项是
continueBatchOnError，默认情况下是true。在这些情况下，另一种方法是尝试插入所有mail_id值并检查批返回的更新计数。成功的插入将返回一个UPDATECONTUT为1，而由于现有的mail_id失败的插入将返回EXECUTE_FAILED（-3）。然后，我们可以通过“cc>”检索成功插入的（new）id值，然后继续创建SELECT语句返回并检索已经存在的.getGeneratedKeys()条目的id值。所以像这样的代码
// 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>
会产生如下控制台输出：
mailIdMap now contains:
11 - 17
12 - null
13 - 19
SELECT id, mail_id FROM mail_contacts WHERE mail_id IN (12)
其余过程将与之前相同：
填写剩余的
mail_id条目，然后使用
mailIdMap中的id值处理另一个表上的插入。关于java - 在表中添加具有唯一列的行:获取现有ID值以及新创建的ID值，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/26858270/