将行插入Postgres时出现空指针异常

Question

I am querying a table in Postgres to see if a row with primary key values match those in a given Map exists. If there are no results, I want to insert a new row. I can do this just fine when I go the standard JDBC route of creating a prepared statement and explicitly setting all the column values, but I want a more generic approach with the help of Groovy's Sql class.

This is my insert statement (the primary key columns are the first three):

insert into MY_TABLE
  (contract_month, contract_year, publish_date, open, high, low)
values
  (10, 2015, 2015-09-15 00:00:00.0, 46.65, 46.9, 45.98)

The issue is that I'm getting a NullPointerException from the Postgres driver as soon as I insert a row:

Exception in thread "main" java.lang.NullPointerException
    at org.postgresql.core.v3.SimpleParameterList.setNull(SimpleParameterList.java:142)
    at org.postgresql.jdbc2.AbstractJdbc2Statement.setNull(AbstractJdbc2Statement.java:1259)
    at org.postgresql.jdbc3.AbstractJdbc3Statement.setNull(AbstractJdbc3Statement.java:1499)
    at org.postgresql.jdbc4.AbstractJdbc4Statement.setNull(AbstractJdbc4Statement.java:85)
    at org.postgresql.jdbc2.AbstractJdbc2Statement.setObject(AbstractJdbc2Statement.java:2092)
    at org.postgresql.jdbc3g.AbstractJdbc3gStatement.setObject(AbstractJdbc3gStatement.java:38)
    at org.postgresql.jdbc4.AbstractJdbc4Statement.setObject(AbstractJdbc4Statement.java:48)

Digging into it, I find that an object called ProtoConnection is null in the org.postgresql.core.v3.SimpleParameterList class. What am I doing wrong?

This is the wrapping code which creates the Sql object:

  private Main() {    
    final def headers = new HashMap<Integer, String>()
    final def record = new HashMap<String, Object>()

    Sql.withInstance(/* my db */) { final Sql sql ->
      sql.withBatch {
        new URL(/* my url */).withReader {
          it.readLines().each {
            if (headers.isEmpty()) {
              setHeaders it, headers
            }
            else {
              processRecord it, headers, record
              storeRecord sql, record
            }
          }
        }
      }
    }
  }

And this is the database logic. The error occurs at the very last line:

def storeRecord = { final Sql sql, final Map<String, Object> record ->
    final def connection = sql.connection
    final def metadata = connection.metaData

    final def columns = metadata.getColumns(null, null, MY_TABLE, null).with {
      final def result = []
      while (it.next()) {
        result << it.getString(4)
      }
      result
    }

    final def primaryKeys = metadata.getPrimaryKeys(null, null, MY_TABLE).with {
      final def result = []
      while (it.next()) {
        result << it.getString(4)
      }
      result
    }

    final def whereClause = primaryKeys.collect { final String pk ->
      "$pk = ?.$pk"
    }

    final def select = """
        select ${columns.join(', ')}
          from MY_TABLE
         where ${whereClause.join(' and ')}
        """

    final def row = sql.firstRow(select, record)

    if (row) {
      println "Updating"
      // Not implemented yet
    }
    else {
      println "Inserting record: $record"
      final def insert = """
                insert into MY_TABLE
                  (${columns.findAll { null != record[it] }.join(", ")})
                 values
                  (${columns.findAll { null != record[it] }.collect { record[it] }.join(", ")})
                """
      println insert
      sql.executeInsert(insert, record)
    }

Answer 1

There were a few things I was doing wrong with my code. First of all, I wasn't converting the string objects in the record map into the appropriate JDBC types. This explains why I was able to insert records via the standard prepared statement route, as I originally did the conversion there, and overlooked it when transitioning to Groovy's API.

After fixing this, I then got an error that the hstore extension was not supported. This was simply solved by executing create extension hstore in Postgres.

Finally, I received an index out of bounds error. This was due to a silly bug in my code where I was setting the values in my insert statement, rather than letting the API fill in the parameters. You can see this fix in the final line of the insert statement now:

final def insert = """
    insert into MY_TABLE
      (${columns.join(', ')})
     values
      (${columns.collect { "?.$it" }.join(', ')})
    """
sql.executeInsert(insert, record)