Java 从数据库检索数据时出现空指针异常
我试图使用JavaJDBC连接从数据库中的相应源系统检索表名、表中所有行的计数、最大更新时间戳和。到目前为止,这就是我想到的Java 从数据库检索数据时出现空指针异常,java,jdbc,Java,Jdbc,我试图使用JavaJDBC连接从数据库中的相应源系统检索表名、表中所有行的计数、最大更新时间戳和。到目前为止,这就是我想到的 public Map<String,Long> getGpTableCount() throws SQLException { List<String> gpTableList = getChunks(); // sourcedb.tablenamename,targetdb.
public Map<String,Long> getGpTableCount() throws SQLException {
List<String> gpTableList = getChunks(); // sourcedb.tablenamename,targetdb.tablename:SSN
Iterator<String> keySetIterator_gpTableList = gpTableList.iterator(); // sourcedb.tablename,targetdb.tablename:SSN
Connection sourcedbCon = (Connection) DbManager.getGpConnection();
PreparedStatement gp_pstmnt = null;
String gpExcpnMsg;
while(keySetIterator_gpTableList.hasNext()) {
String gpTabSchemakey = keySetIterator_gpTableList.next(); // sourcedb.tablename,targetdb.tablename:SSN
String[] tablesnSSNs = gpTabSchemakey.split(","); // tablesnSSNs[0]: sourcedb.tablename, tablesnSSNs[1]: targetdb.tablename:SSN
String[] target = tablesnSSNs[1].split(":"); // target[0]=targetdb.tablename, target[1]=SSN
String[] sourcedbTable = target[0].split("\\."); // sourcedbTable[0] = targetdb, sourcedbTable[1]=table
String gpCountQuery = "select '" + sourcedbTable[1] + "' as TableName, count(*) as Count, source_system_name, max(xx_last_update_tms) from " + tablesnSSNs[0] + " where source_system_name = '" + target[1] + "' group by source_system_name";
System.out.println("\nGP Query: " + gpCountQuery);
try {
gp_pstmnt = sourcedbCon.prepareStatement(gpCountQuery);
ResultSet gpCountRs = gp_pstmnt.executeQuery(); // gpCountRs(1): table, gpCountRs(2): count, gpCountRs(3): source_system_name, gpCountRs(4): max(xx_last_update_tms)
while(gpCountRs.next()) {
System.out.println("sourcedbTable[1]: " + sourcedbTable[1] + " gpCountRs.getString(3): " + gpCountRs.getString(3) + " gpCountRs.getLong(2): " + gpCountRs.getLong(2));
gpCountMap.put(sourcedbTable[1] + "," + gpCountRs.getString(3), gpCountRs.getLong(2)); // (tableName,ssn,12345678)
}
} catch(org.postgresql.util.PSQLException e) {
System.out.println("In SQL Exception block");
gpExcpnMsg = e.getMessage();
gpTabNotFound.put(gpCountQuery, gpExcpnMsg + "\n");
} catch(SQLException e) {
e.printStackTrace();
} catch(Exception e) {
System.out.println("In Exception block");
gpExcpnMsg = e.getMessage();
e.printStackTrace();
}
}
System.out.println("GP Connection closed");
gp_pstmnt.close();
sourcedbCon.close();
return gpCountMap;
}
异常对应的行位于:
gpCountMap.put(analyticsTable[1] + "," + gpCountRs.getString(3), gpCountRs.getLong(2));
这是我的主要课程:
public class StartCount {
public static void main(String[] args) throws SQLException, IOException, AddressException, InterruptedException {
ChunkData chData = new ChunkData();
chData.getGpTableCount();
}
}
我试图调试代码,但我无法理解我所犯的错误。
有人能告诉我如何修复此问题吗?根据您的代码,
gpCountMap
为空,您已将其设置为全局变量,但未对其进行初始化
为了解决这个问题,只需在getGpTableCount
gpCountMap = new HashMap<String,Long>();
可能您正在对统一化对象调用
getGpTableCount
。如果你不告诉我们你叫它什么,我们就不知道了。gpCountMap
的定义在哪里?您可能没有initit@Ben我在调用该方法的地方添加了main类。@lucumt我已将其声明为global as->Map gpCountMap@Sidhartha您在哪里初始化了gpCountMap。你提到的只是声明
gpCountMap = new HashMap<String,Long>();
public static void main(String[] args) throws SQLException, IOException, AddressException, InterruptedException {
ChunkData chData = new ChunkData();
chData.getGpTableCount();
gpCountMap = new HashMap<String,Long>();
}