Why resultset is null

Released as part of JDK 1. Can we return ResultSet in Java? To return result sets from a Java method Ensure that the Java method is declared as public and static in a public class. For each result set you expect the method to return, ensure that the method has a parameter of type java.

What does setAutoCommit false do? This transaction will be committed when connection. What is result set in JDBC? ResultSet interface represents the result set of a database query. A ResultSet object maintains a cursor that points to the current row in the result set. The term "result set" refers to the row and column data contained in a ResultSet object.

A ResultSet object is a table of data representing a database result set, which is usually generated by executing a statement that queries the database.

For example, the CoffeeTables. How do you handle null values in Java? But enough bragging, here's my list of practices when dealing with null values. Don't Overcomplicate Things. Use Objects Methods as Stream Predicates. Never Pass Null as an Argument. Leverage Optional. Return Empty Collections Instead of Null. Optional Ain't for Fields.

Clob value. Date value. NClob value. Ref value. Time value. Timestamp value. Methods inherited from interface java.

This constant is used by the method setFetchDirection as a hint to the driver, which the driver may ignore. Since: 1. A ResultSet cursor is initially positioned before the first row; the first call to the method next makes the first row the current row; the second call makes the second row the current row, and so on. When a call to the next method returns false , the cursor is positioned after the last row. If an input stream is open for the current row, a call to the method next will implicitly close it.

A ResultSet object's warning chain is cleared when a new row is read. Returns: true if the new current row is valid; false if there are no more rows Throws: SQLException - if a database access error occurs or this method is called on a closed result set close void close throws SQLException Releases this ResultSet object's database and JDBC resources immediately instead of waiting for this to happen when it is automatically closed.

Blob , Clob or NClob objects remain valid for at least the duration of the transaction in which they are creataed, unless their free method is invoked. Note: A ResultSet object is automatically closed by the Statement object that generated it when that Statement object is closed, re-executed, or is used to retrieve the next result from a sequence of multiple results. Calling the method close on a ResultSet object that is already closed is a no-op.

Note that you must first call one of the getter methods on a column to try to read its value and then call the method wasNull to see if the value read was SQL NULL. Parameters: columnIndex - the first column is 1, the second is 2, Returns: the column value; if the value is SQL NULL , the value returned is null Throws: SQLException - if the columnIndex is not valid; if a database access error occurs or this method is called on a closed result set getBoolean boolean getBoolean int columnIndex throws SQLException Retrieves the value of the designated column in the current row of this ResultSet object as a boolean in the Java programming language.

Retrieves the value of the designated column in the current row of this ResultSet object as a java. BigDecimal in the Java programming language. The bytes represent the raw values returned by the driver. The value can then be read in chunks from the stream. Note: All the data in the returned stream must be read prior to getting the value of any other column.

The next call to a getter method implicitly closes the stream. Also, a stream may return 0 when the method InputStream.

The first byte is the high byte; the second byte is the low byte. Returns: a Java input stream that delivers the database column value as a stream of uninterpreted bytes; if the value is SQL NULL , the value returned is null Throws: SQLException - if the columnIndex is not valid; if a database access error occurs or this method is called on a closed result set getString String getString String columnLabel throws SQLException Retrieves the value of the designated column in the current row of this ResultSet object as a String in the Java programming language.

Also, a stream may return 0 when the method available is called whether there is data available or not. The JDBC technology-enabled driver will do any necessary conversion from the database format into Unicode. If the SQL AS clause was not specified, then the label is the name of the column Returns: a Java input stream that delivers the database column value as a stream of two-byte Unicode characters.

The warning chain is automatically cleared each time a new row is read. This method may not be called on a ResultSet object that has been closed; doing so will cause an SQLException to be thrown.

Note: This warning chain only covers warnings caused by ResultSet methods. Any warning caused by Statement methods such as reading OUT parameters will be chained on the Statement object. After this method is called, the method getWarnings returns null until a new warning is reported for this ResultSet object.

In SQL, a result table is retrieved through a cursor that is named. Returns: the description of this ResultSet object's columns Throws: SQLException - if a database access error occurs or this method is called on a closed result set getObject Object getObject int columnIndex throws SQLException Gets the value of the designated column in the current row of this ResultSet object as an Object in the Java programming language.

This method will return the value of the given column as a Java object. The type of the Java object will be the default Java object type corresponding to the column's SQL type, following the mapping for built-in types specified in the JDBC specification. This method may also be used to read database-specific abstract data types. In the JDBC 2. If Connection. Returns: a java. Object holding the column value Throws: SQLException - if the columnIndex is not valid; if a database access error occurs or this method is called on a closed result set getObject Object getObject String columnLabel throws SQLException Gets the value of the designated column in the current row of this ResultSet object as an Object in the Java programming language.

When a column contains a structured or distinct value, the behavior of this method is as if it were a call to: getObject columnIndex, this. If the SQL AS clause was not specified, then the label is the name of the column Returns: the column index of the given column name Throws: SQLException - if the ResultSet object does not contain a column labeled columnLabel , a database access error occurs or this method is called on a closed result set getCharacterStream Reader getCharacterStream int columnIndex throws SQLException Retrieves the value of the designated column in the current row of this ResultSet object as a java.

Throws: SQLException - if the columnIndex is not valid; if a database access error occurs or this method is called on a closed result set Since: 1. Reader object that contains the column value; if the value is SQL NULL , the value returned is null in the Java programming language Throws: SQLException - if the columnLabel is not valid; if a database access error occurs or this method is called on a closed result set Since: 1. Throws: SQLException - if the columnLabel is not valid; if a database access error occurs or this method is called on a closed result set Since: 1.

Note: Calling the method isLast may be expensive because the JDBC driver might need to fetch ahead one row in order to determine whether the current row is the last row in the result set. This method has no effect if the result set contains no rows. The first row is number 1, the second number 2, and so on.

If the row number is positive, the cursor moves to the given row number with respect to the beginning of the result set. The first row is row 1, the second is row 2, and so on. If the given row number is negative, the cursor moves to an absolute row position with respect to the end of the result set. For example, calling the method absolute -1 positions the cursor on the last row; calling the method absolute -2 moves the cursor to the next-to-last row, and so on.

If the row number specified is zero, the cursor is moved to before the first row. Note: Calling absolute 1 is the same as calling first. Calling absolute -1 is the same as calling last. Parameters: row - the number of the row to which the cursor should move. Calling relative 0 is valid, but does not change the cursor position. Note: Calling the method relative 1 is identical to calling the method next and calling the method relative -1 is identical to calling the method previous.

When a call to the previous method returns false , the cursor is positioned before the first row. If an input stream is open for the current row, a call to the method previous will implicitly close it. A ResultSet object's warning change is cleared when a new row is read. The initial value is determined by the Statement object that produced this ResultSet object. The fetch direction may be changed at any time.

Parameters: direction - an int specifying the suggested fetch direction; one of ResultSet. Returns: the current fetch direction for this ResultSet object Throws: SQLException - if a database access error occurs or this method is called on a closed result set Since: 1. If the fetch size specified is zero, the JDBC driver ignores the value and is free to make its own best guess as to what the fetch size should be. The default value is set by the Statement object that created the result set.

The fetch size may be changed at any time. Returns: the current fetch size for this ResultSet object Throws: SQLException - if a database access error occurs or this method is called on a closed result set Since: 1. The type is determined by the Statement object that created the result set. Returns: ResultSet.

The concurrency used is determined by the Statement object that created the result set. Returns: the concurrency type, either ResultSet. The value returned depends on whether or not the result set can detect updates. The value returned depends on whether or not this ResultSet object can detect visible inserts.

A deleted row may leave a visible "hole" in a result set. This method can be used to detect holes in a result set. The value returned depends on whether or not this ResultSet object can detect deletions. The updater methods are used to update column values in the current row or the insert row.

The updater methods do not update the underlying database; instead the updateRow or insertRow methods are called to update the database. If the second argument is an InputStream then the stream must contain the number of bytes specified by scaleOrLength. If the second argument is a Reader then the reader must contain the number of characters specified by scaleOrLength. If these conditions are not true the driver will generate a SQLException when the statement is executed.

BigDecimal , this is the number of digits after the decimal point. For Java Object types InputStream and Reader , this is the length of the data in the stream or reader.

For all other types, this value will be ignored. If the SQL AS clause was not specified, then the label is the name of the column x - the new column value scaleOrLength - for an object of java. The cursor must be on the insert row when this method is called. This method cannot be called when the cursor is on the insert row. The refreshRow method provides a way for an application to explicitly tell the JDBC driver to refetch a row s from the database. An application may want to call refreshRow when caching or prefetching is being done by the JDBC driver to fetch the latest value of a row from the database.

The JDBC driver may actually refresh multiple rows at once if the fetch size is greater than one. All values are refetched subject to the transaction isolation level and cursor sensitivity. If refreshRow is called after calling an updater method, but before calling the method updateRow , then the updates made to the row are lost. Provide the stack trace, that would help. The String being null is a very good chance, but when you see values in your table, yet a null is printed by the ResultSet, it might mean that the connection was closed before the value of ResultSet was used.

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