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Oracle® Database JDBC Developer's Guide and Reference
10g Release 2 (10.2)

Part Number B14355-01
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13 Accessing and Manipulating Oracle Data

This chapter describes data access in oracle.sql.* formats, as opposed to standard Java formats. The oracle.sql.* formats are a key factor of the Oracle Java Database Connectivity (JDBC) extensions, offering significant advantages in efficiency and precision in manipulating SQL data.

Using oracle.sql.* formats involves casting your result sets and statements to OracleResultSet, OracleStatement, OraclePreparedStatement, and OracleCallableStatement, as appropriate, and using the getOracleObject, setOracleObject, getXXX, and setXXX methods of these classes, where XXX corresponds to the types in the oracle.sql package.

This chapter covers the following topics:

13.1 Data Type Mappings

The Oracle JDBC drivers support standard JDBC types as well as Oracle-specific data types. This section documents standard and Oracle-specific SQL-Java default type mappings. This section contains the following topics:

13.1.1 Table of Mappings

Table 13-1 shows the default mappings between SQL data types, JDBC type codes, standard Java types, and Oracle extended types.

The SQL Data Types column lists the SQL types that exist in Oracle Database 10g. The JDBC Type Codes column lists data type codes supported by the JDBC standard and defined in the java.sql.Types class or by Oracle in the oracle.jdbc.OracleTypes class. For standard type codes, the codes are identical in these two classes.

The Standard Java Types column lists standard types defined in the Java language. The Oracle Extension Java Types column lists the oracle.sql.* Java types that correspond to each SQL data type in the database. These are Oracle extensions that let you retrieve all SQL data in the form of a oracle.sql.* Java type. Manipulating SQL data as oracle.sql.* data types minimizes conversions, improving performance and eliminating conversion losses.

Table 13-1 Default Mappings Between SQL Types and Java Types

SQL Data Types JDBC Type Codes Standard Java Types Oracle Extension Java Types

STANDARD JDBC 1.0 TYPES:

CHAR java.sql.Types.CHAR java.lang.String oracle.sql.CHAR
VARCHAR2 java.sql.Types.VARCHAR java.lang.String oracle.sql.CHAR
LONG java.sql.Types.LONGVARCHAR java.lang.String oracle.sql.CHAR
NUMBER java.sql.Types.NUMERIC java.math.BigDecimal oracle.sql.NUMBER
NUMBER java.sql.Types.DECIMAL java.math.BigDecimal oracle.sql.NUMBER
NUMBER java.sql.Types.BIT boolean oracle.sql.NUMBER
NUMBER java.sql.Types.TINYINT byte oracle.sql.NUMBER
NUMBER java.sql.Types.SMALLINT short oracle.sql.NUMBER
NUMBER java.sql.Types.INTEGER int oracle.sql.NUMBER
NUMBER java.sql.Types.BIGINT long oracle.sql.NUMBER
NUMBER java.sql.Types.REAL float oracle.sql.NUMBER
NUMBER java.sql.Types.FLOAT double oracle.sql.NUMBER
NUMBER java.sql.Types.DOUBLE double oracle.sql.NUMBER
RAW java.sql.Types.BINARY byte[] oracle.sql.RAW
RAW java.sql.Types.VARBINARY byte[] oracle.sql.RAW
LONGRAW java.sql.Types.LONGVARBINARY byte[] oracle.sql.RAW
DATE java.sql.Types.DATE java.sql.Date oracle.sql.DATE
DATE java.sql.Types.TIME java.sql.Time oracle.sql.DATE
TIMESTAMP java.sql.Types.TIMESTAMP javal.sql.Timestamp oracle.sql.TIMESTAMP

STANDARD JDBC 2.0 TYPES:

BLOB java.sql.Types.BLOB java.sql.Blob oracle.sql.BLOB
CLOB java.sql.Types.CLOB java.sql.Clob oracle.sql.CLOB
user-defined object java.sql.Types.STRUCT java.sql.Struct oracle.sql.STRUCT
user-defined reference java.sql.Types.REF java.sql.Ref oracle.sql.REF
user-defined collection java.sql.Types.ARRAY java.sql.Array oracle.sql.ARRAY

ORACLE EXTENSIONS:

BFILE oracle.jdbc.OracleTypes.BFILE NA oracle.sql.BFILE
ROWID oracle.jdbc.OracleTypes.ROWID NA oracle.sql.ROWID
REF CURSOR oracle.jdbc.OracleTypes.CURSOR java.sql.ResultSet oracle.jdbc.OracleResultSet
TIMESTAMP oracle.jdbc.OracleTypes.TIMESTAMP java.sql.Timestamp oracle.sql.TIMESTAMP
TIMESTAMP WITH TIME ZONE oracle.jdbc.OracleTypes.TIMESTAMPTZ java.sql.Timestamp oracle.sql.TIMESTAMPTZ
TIMESTAMP WITH LOCAL TIME ZONE oracle.jdbc.OracleTypes.TIMESTAMPLTZ java.sql.Timestamp oracle.sql.TIMESTAMPLTZ


Note:

For database versions, such as 8.1.7, which do not support the TIMESTAMP data type, TIMESTAMP is mapped to DATE.

13.1.2 Notes Regarding Mappings

This section provides further detail regarding mappings for NUMBER and user-defined types.

NUMBER Types

For the different type codes that an Oracle NUMBER value can correspond to, call the getter routine that is appropriate for the size of the data for mapping to work properly. For example, call getByte to get a Java tinyint value for an item x, where -128 < x < 128.

User-Defined Types

User-defined types, such as objects, object references, and collections, map by default to weak Java types, such as java.sql.Struct, but alternatively can map to strongly typed custom Java classes. Custom Java classes can implement one of two interfaces:

  • The standard java.sql.SQLData

  • The Oracle-specific oracle.sql.ORAData

13.2 Data Conversion Considerations

When JDBC programs retrieve SQL data into Java, you can use standard Java types, or you can use types of the oracle.sql package. This section covers the following topics:

13.2.1 Standard Types Versus Oracle Types

The Oracle data types in oracle.sql store data in the same bit format as used by the database. In versions of the Oracle JDBC drivers prior to Oracle Database 10g, the Oracle data types were generally more efficient. The Oracle Database 10g JDBC drivers were substantially updated. As a result, in most cases the standard Java types are preferred to the data types in oracle.sql. In particular, java.lang.String is much more efficient than oracle.sql.CHAR.

In general, Oracle recommends that you use the Java standard types. The exceptions to this are:

  • Use the oracle.sql.OraData rather than the java.sql.SqlData if the OraData functionality better suits your needs.

  • Use oracle.sql.NUMBER rather than java.lang.Double if you need to retain the exact values of floating point numbers. Oracle NUMBER is a decimal representation and Java Double and Float are binary representations. Conversion from one format to the other can result in slight variations in the actual value represented. Additionally, the range of values that can be represented using the two formats is different.

  • Use oracle.sql.DATE or oracle.sql.TIMESTAMP rather than java.sql.Date or java.sql.Timestamp if you are using JDK 5.0 or earlier versions or require maximum performance. You may also use the oracle.sql data type if you want to read many date values or compute or display only a small percentage. Due to a bug in all versions of Java prior to JDK 5.1, construction of java.lang.Date and java.lang.Timestamp objects is slow, especially in multithreaded environments. This bug is fixed in JDK 5.1.


Note:

If you convert an oracle.sql data type to a Java standard data type, then the benefits of using the oracle.sql data type are lost.

13.2.2 Converting SQL NULL Data

Java represents a SQL NULL datum by the Java value null. Java data types fall into two categories: primitive types, such as byte, int, and float, and object types, such as class instances. The primitive types cannot represent null. Instead, they store null as the value zero, as defined by the JDBC specification. This can lead to ambiguity when you try to interpret your results.

In contrast, Java object types can represent null. The Java language defines an object wrapper type corresponding to every primitive type that can represent null. The object wrapper types must be used as the targets for SQL data to detect SQL NULL without ambiguity.

13.2.3 Testing for NULLs

You cannot use a relational operator to compare NULL values with each other or with other values. For example, the following SELECT statement does not return any row even if the COMM column contains one or more NULL values.

PreparedStatement pstmt = conn.prepareStatement(
  "SELECT * FROM EMP WHERE COMM = ?"); 
pstmt.setNull(1, java.sql.Types.VARCHAR); 

The next example shows how to compare values for equality when some return values might be NULL. The following code returns all the ENAMES from the EMP table that are NULL, if there is no value of 100 for COMM.

PreparedStatement pstmt = conn.prepareStatement("SELECT ENAME FROM EMP 
  WHERE COMM =? OR  ((COMM IS NULL) AND (? IS NULL))"); 
pstmt.setBigDecimal(1, new BigDecimal(100)); 
pstmt.setNull(2, java.sql.Types.VARCHAR); 

13.3 Result Set and Statement Extensions

The JDBC Statement object returns an OracleResultSet object, typed as a java.sql.ResultSet. If you want to apply only standard JDBC methods to the object, then keep it as a ResultSet type. However, if you want to use the Oracle extensions on the object, then you must cast it to OracleResultSet. All of the Oracle ResultSet extensions are in the oracle.jdbc.OracleResultSet interface and all the Statement extensions are in the oracle.jdbc.OracleStatement interface.

For example, assuming you have a standard Statement object stmt, do the following if you want to use only standard JDBC ResultSet methods:

ResultSet rs = stmt.executeQuery("SELECT * FROM emp");

If you need the extended functionality provided by the Oracle extensions to JDBC, you can select the results into a standard ResultSet variable and then cast that variable to OracleResultSet later.

Similarly, when you use executeQuery to run a stored procedure using a callable statement, the returned object is an OracleCallableStatement. The type of the return value of executeQuery() is java.sql.CallableStatement. If your application needs only the standard JDBC methods, you need not cast the variable. However, to take advantage of the Oracle extensions, you must cast the variable to OracleCallableStatement. Similar rules apply to prepareStatement, prepareCall, and so on.

Key extensions to the result set and statement classes include the getOracleObject and setOracleObject methods, used to access and manipulate data in oracle.sql.* formats.

13.4 Comparison of Oracle get and set Methods to Standard JDBC

This section describes get and set methods, particularly the JDBC standard getObject and setObject methods and the Oracle-specific getOracleObject and setOracleObject methods, and how to access data in oracle.sql.* format compared with Java format.

Although there are specific getXXX methods for all the Oracle SQL types, you can use the general get methods for convenience or simplicity, or if you are not certain in advance what type of data you will receive.

This section covers the following topics:


Note:

You cannot qualify a column name with a table name and pass it as a parameter to the getXXX method. For example:
ResultSet rset = stmt.executeQuery("SELECT emp.deptno, dept.deptno FROM emp, dept");
rset.getInt("emp.deptno");

The getInt method in the preceding code will throw an exception. To uniquely identify the columns in the getXXX method, you can either use column index or specify column aliases in the query and use these aliases in the getXXX method.


13.4.1 Standard getObject Method

The standard getObject method of a result set or callable statement has a return type of java.lang.Object. The class of the object returned is based on its SQL type, as follows:

  • For SQL data types that are not Oracle-specific, getObject returns the default Java type corresponding to the SQL type of the column, following the mapping in the JDBC specification.

  • For Oracle-specific data types, getObject returns an object of the appropriate oracle.sql.* class, such as oracle.sql.ROWID.

  • For Oracle database objects, getObject returns a Java object of the class specified in your type map. Type maps specify a mapping from database named types to Java classes. The getObject(parameter_index) method uses the default type map of the connection. The getObject(parameter_index, map) enables you to pass in a type map. If the type map does not provide a mapping for a particular Oracle object, then getObject returns an oracle.sql.STRUCT object.

13.4.2 Oracle getOracleObject Method

If you want to retrieve data from a result set or callable statement as an oracle.sql.* object, then you must follow a special process. For a ResultSet, you must cast the result set itself to oracle.jdbc.OracleResultSet and then call getOracleObject instead of getObject. The same applies to CallableStatement and oracle.jdbc.OracleCallableStatement.

The return type of getOracleObject is oracle.sql.Datum. The actual returned object is an instance of the appropriate oracle.sql.* class. The method signature is:

public oracle.sql.Datum getOracleObject(int parameter_index)

When you retrieve data into a Datum variable, you can use the standard Java instanceof operator to determine which oracle.sql.* type it really is.

Example: Using getOracleObject with a ResultSet

The following example creates a table that contains a column of CHAR data and a column containing a BFILE locator. A SELECT statement retrieves the contents of the table as a result set. The getOracleObject then retrieves the CHAR data into the char_datum variable and the BFILE locator into the bfile_datum variable. Note that because getOracleObject returns a Datum object, the return values must be cast to CHAR and BFILE, respectively.

stmt.execute ("CREATE TABLE bfile_table (x VARCHAR2 (30), b BFILE)");
stmt.execute 
    ("INSERT INTO bfile_table VALUES ('one', BFILENAME ('TEST_DIR', 'file1'))");

ResultSet rset = stmt.executeQuery ("SELECT * FROM bfile_table");
while (rset.next ())
{
   CHAR char_datum = (CHAR) ((OracleResultSet)rset).getOracleObject (1);
   BFILE bfile_datum = (BFILE) ((OracleResultSet)rset).getOracleObject (2);
   ...
}

Example: Using getOracleObject in a Callable Statement

The following example prepares a call to the procedure myGetDate, which associates a character string with a date. The program passes "SCOTT" to the prepared call and registers the DATE type as an output parameter. After the call is run, getOracleObject retrieves the date associated with "SCOTT". Note that because getOracleObject returns a Datum object, the results are cast to DATE.

OracleCallableStatement cstmt = (OracleCallableStatement)conn.prepareCall
                                   ("begin myGetDate (?, ?); end;");

cstmt.setString (1, "SCOTT");
cstmt.registerOutParameter (2, Types.DATE);
cstmt.execute ();

DATE date = (DATE) ((OracleCallableStatement)cstmt).getOracleObject (2);
...

13.4.3 Summary of getObject and getOracleObject Return Types

Table 13-2 lists the underlying return types for the getObject and getOracleObject methods for each Oracle SQL type.

Keep in mind the following when you use these methods:

  • getObjectalways returns data into a java.lang.Object instance

  • getOracleObject always returns data into an oracle.sql.Datum instance

You must cast the returned object to use any special functionality.

Table 13-2 getObject and getOracleObject Return Types

Oracle SQL Type getObject Underlying Return Type getOracleObject Underlying Return Type
CHAR String oracle.sql.CHAR
VARCHAR2 String oracle.sql.CHAR
LONG String oracle.sql.CHAR
NUMBER java.math.BigDecimal oracle.sql.NUMBER
RAW byte[] oracle.sql.RAW
LONGRAW byte[] oracle.sql.RAW
DATE java.sql.Date oracle.sql.DATE
TIMESTAMP java.sql.TimestampFoot 1  oracle.sql.TIMESTAMP
TIMESTAMP WITH TIME ZONE oracle.sql.TIMESTAMPTZ oracle.sql.TIMESTAMPTZ
TIMESTAMP WITH LOCAL TIME ZONE oracle.sql.TIMESTAMPLTZ oracle.sql.TIMESTAMPLTZ
BINARY_FLOAT java.lang.Float oracle.sql.BINARY_FLOAT
BINARY_DOUBLE java.lang.Double oracle.sql.BINARY_DOUBLE
INTERVAL DAY TO SECOND oracle.sql.INTERVALDS oracle.sql.INTERVALDS
INTERVAL YEAR TO MONTH oracle.sql.INTERVALYM oracle.sql.INTERVALYM
ROWID oracle.sql.ROWID oracle.sql.ROWID
REF CURSOR java.sql.ResultSet (not supported)
BLOB oracle.sql.BLOB oracle.sql.BLOB
CLOB oracle.sql.CLOB oracle.sql.CLOB
BFILE oracle.sql.BFILE oracle.sql.BFILE
Oracle object class specified in type map

or oracle.sql.STRUCT (if no type map entry)

oracle.sql.STRUCT
Oracle object reference oracle.sql.REF oracle.sql.REF
collection (varray or nested table) oracle.sql.ARRAY oracle.sql.ARRAY

Footnote 1 ResultSet.getObject returns java.sql.Timestamp only if the oracle.jdbc.J2EE13Compliant connection property is set to TURE, else the method returns oracle.sql.TIMESTAMP.

Note:

The ResultSet.getObject method returns java.sql.Timestamp for the TIMESTAMP SQL type, only when the connection property oracle.jdbc.J2EE13Compliant is set to TRUE. This property has to be set when the connection is obtained. If this connection property is not set or if it is set after the connection is obtained, then the ResultSet.getObject method returns oracle.sql.TIMESTAMP for the TIMESTAMP SQL type.

The oracle.jdbc.J2EE13Compliant connection property can also be set without changing the code in the following ways:

  • Including the classes12dms.jar and ojdbc14dms.jar files in CLASSPATH. These files set oracle.jdbc.J2EE13Compliant to TRUE by default. These files are located in $ORACLE_HOME/jdbc/lib.

  • Setting the system property by calling the java command with the flag -Doracle.jdbc.J2EE13Compliant=true. For example,

    java -Doracle.jdbc.J2EE13Compliant=true ...
    
    

When the J2EE13Compliant is set to TRUE the behaviour is as in Table B-3 of the JDBC specification.



See Also:

Table A-1, "Valid SQL Data Type-Java Class Mappings", for information on type compatibility between all SQL and Java types.

13.4.4 Other getXXX Methods

Standard JDBC provides a getXXX for each standard Java type, such as getByte, getInt, getFloat, and so on. Each of these returns exactly what the method name implies.

In addition, the OracleResultSet and OracleCallableStatement classes provide a full complement of getXXX methods corresponding to all the oracle.sql.* types. Each getXXX method returns an oracle.sql.XXX object. For example, getROWID returns an oracle.sql.ROWID object.

There is no performance advantage in using the specific getXXX methods. However, they do save you the trouble of casting, because the return type is specific to the object being returned.

This section covers the following topics:

13.4.4.1 Return Types of getXXX Methods

Table 13-3 summarizes the return types for each getXXX method and specifies which are Oracle extensions under Java Development Kit (JDK) 1.2.x. You must cast the returned object to OracleResultSet or OracleCallableStatement to use methods that are Oracle extensions.

Table 13-3 Summary of getXXX Return Types

Method Return Type (type in method signature) Type of returned object Oracle Ext for JDK 1.2.x?
getArray java.sql.Array oracle.sql.ARRAY No
getARRAY oracle.sql.ARRAY oracle.sql.ARRAY Yes
getAsciiStream java.io.InputStream java.io.InputStream No
getBfile oracle.sql.BFILE oracle.sql.BFILE Yes
getBFILE oracle.sql.BFILE oracle.sql.BFILE Yes
getBigDecimal (see Notes) java.math.BigDecimal java.math.BigDecimal No
getBinaryStream java.io.InputStream java.io.InputStream No
getBlob java.sql.Blob oracle.sql.BLOB No
getBLOB oracle.sql.BLOB oracle.sql.BLOB Yes
getBoolean (see Notes) boolean boolean No
getByte byte byte No
getBytes byte[] byte[] No
getCHAR oracle.sql.CHAR oracle.sql.CHAR Yes
getCharacterStream java.io.Reader java.io.Reader No
getClob java.sql.Clob oracle.sql.CLOB No
getCLOB oracle.sql.CLOB oracle.sql.CLOB Yes
getDate java.sql.Date java.sql.Date No
getDATE oracle.sql.DATE oracle.sql.DATE Yes
getDouble double double No
getFloat float float No
getInt int int No
getINTERVALDS oracle.sql.INTERVALDS oracle.sql.INTERVALDS Yes
getINTERVALYM oracle.sql.INTERVALYM oracle.sql.INTERVALYM Yes
getLong long long No
getNUMBER oracle.sql.NUMBER oracle.sql.NUMBER Yes
getOracleObject oracle.sql.Datum subclasses of oracle.sql.Datum Yes
getRAW oracle.sql.RAW oracle.sql.RAW Yes
getRef java.sql.Ref oracle.sql.REF No
getREF oracle.sql.REF oracle.sql.REF Yes
getROWID oracle.sql.ROWID oracle.sql.ROWID Yes
getShort short short No
getString String String No
getSTRUCT oracle.sql.STRUCT oracle.sql.STRUCT. Yes
getTime java.sql.Time java.sql.Time No
getTimestamp java.sql.Timestamp java.sql.Timestamp No
getTIMESTAMP oracle.sql.TIMESTAMP oracle.sql.TIMESTAMP Yes
getTIMESTAMPTZ oracle.sql.TIMESTAMPTZ oracle.sql.TIMESTAMPTZ Yes
getTIMESTAMPLTZ oracle.sql.TIMESTAMPLTZ oracle.sql.TIMESTAMPLTZ Yes
getUnicodeStream java.io.InputStream java.io.InputStream No
getURL java.net.URL java.net.URL No

13.4.4.2 Special Notes about getXXX Methods

This section provides additional details about some getXXX methods.

getBigDecimal

JDBC 2.0 simplified method signatures for the getBigDecimal method. The previous input signatures were:

(int columnIndex, int scale) or (String columnName, int scale)

The simplified input signature is:

(int columnIndex) or (String columnName)

The scale parameter, used to specify the number of digits to the right of the decimal, is no longer necessary. The Oracle JDBC drivers retrieve numeric values with full precision.

getBoolean

Because there is no BOOLEAN database type, when you use getBoolean a data type conversion always occurs. The getBoolean method is supported only for numeric columns. When applied to these columns, getBoolean interprets any zero value as false and any other value as true. When applied to any other sort of column, getBoolean raises the exception java.lang.NumberFormatException.

13.4.5 Data Types For Returned Objects from getObject and getXXX

The return type of getObject is java.lang.Object. The returned value is an instance of a subclass of java.lang.Object. Similarly, the return type of getOracleObject is oracle.sql.Datum, and the class of the returned value is a subclass of oracle.sql.Datum. You normally cast the returned object to the appropriate class to use particular methods and functionality of that class.

In addition, you have the option of using a specific getXXX method instead of the generic getObject or getOracleObject methods. The getXXX methods enable you to avoid casting, because the return type of getXXX corresponds to the type of object returned. For example, the return type of getCLOB is oracle.sql.CLOB, as opposed to java.lang.Object.

Example of Casting Return Values

This example assumes that you have fetched data of the NUMBER type as the first column of a result set. Because you want to manipulate the NUMBER data without losing precision, cast your result set to OracleResultSet and use getOracleObject to return the NUMBER data in oracle.sql.* format. If you do not cast your result set, then you have to use getObject, which returns your numeric data into a Java Float and loses some of the precision of your SQL data.

The getOracleObject method returns an oracle.sql.NUMBER object into an oracle.sql.Datum return variable unless you cast the output. Cast the getOracleObject output to oracle.sql.NUMBER if you want to use a NUMBER return variable and any of the special functionality of that class.

NUMBER x = (NUMBER)ors.getOracleObject(1);

Alternatively, you can return the object into a generic oracle.sql.Datum return variable and cast it later when you use NUMBER-specific methods.

Datum rawdatum = ors.getOracleObject(1);
...
CharacterSet cs = ((NUMBER) rawdatum).FIXME();

This uses the FIXME method of oracle.sql.NUMBER. The FIXME method is not defined on oracle.sql.Datum and would not be reachable without the cast.

13.4.6 The setObject and setOracleObject Methods

Just as there is a standard getObject and Oracle-specific getOracleObject in result sets and callable statements, there are also standard setObject and Oracle-specific setOracleObject methods in OraclePreparedStatement and OracleCallableStatement. The setOracleObject methods take oracle.sql.* input parameters.

To bind standard Java types to a prepared statement or callable statement, use the setObject method, which takes a java.lang.Object as input. The setObject method does support a few of the oracle.sql.* types. However, the method has been implemented so that you can enter instances of the oracle.sql.* classes that correspond to the following JDBC standard types: Blob, Clob, Struct, Ref, and Array.

To bind oracle.sql.* types to a prepared statement or callable statement, use the setOracleObject method, which takes a subclass of oracle.sql.Datum as input. To use setOracleObject, you must cast your prepared statement or callable statement to OraclePreparedStatement or OracleCallableStatement.

Example of Using setObject and setOracleObject

For a prepared statement, the setOracleObject method binds the oracle.sql.CHAR data represented by the charVal variable to the prepared statement. To bind the oracle.sql.* data, the prepared statement must be cast to OraclePreparedStatement. Similarly, the setObject method binds the Java String data represented by the variable strVal.

PreparedStatement ps= conn.prepareStatement("text_of_prepared_statement");
((OraclePreparedStatement)ps).setOracleObject(1,charVal);
ps.setObject(2,strVal);

13.4.7 Other setXXX Methods

As with the getXXX methods, there are several specific setXXX methods. Standard setXXX methods are provided for binding standard Java types, and Oracle-specific setXXX methods are provided for binding Oracle-specific types.

Similarly, there are two forms of the setNull method:

  • void setNull(int parameterIndex, int sqlType)

    This is specified in the standard java.sql.PreparedStatement interface. This signature takes a parameter index and a SQL type code defined by the java.sql.Types or oracle.jdbc.OracleTypes class. Use this signature to set an object other than a REF, ARRAY, or STRUCT to NULL.

  • void setNull(int parameterIndex, int sqlType, String sql_type_name)

    With JDBC 2.0, this signature is also specified in the standard java.sql.PreparedStatement interface. This method takes a SQL type name in addition to a parameter index and a SQL type code. Use this method when the SQL type code is java.sql.Types.REF, ARRAY, or STRUCT. If the type code is other than REF, ARRAY, or STRUCT, then the given SQL type name is ignored.

Similarly, the registerOutParameter method has a signature for use with REF, ARRAY, or STRUCT data:

void registerOutParameter
            (int parameterIndex, int sqlType, String sql_type_name)

Binding Oracle-specific types using the appropriate setXXX methods, instead of the methods used for binding standard Java types, may offer some performance advantage.

This section covers the following topics:

13.4.7.1 Input Parameter Types of setXXX Methods

Table 13-4 summarizes the input types for all the setXXX methods and specifies which are Oracle extensions under JDK 1.2.x. To use methods that are Oracle extensions, you must cast your statement to OraclePreparedStatement or OracleCallableStatement.

Table 13-4 Summary of setXXX Input Parameter Types

Method Input Parameter Type Oracle Ext for JDK 1.2.x?
setArray java.sql.Array No
setARRAY oracle.sql.ARRAY Yes
setAsciiStream (see Notes section) java.io.InputStream No
setBfile oracle.sql.BFILE Yes
setBFILE oracle.sql.BFILE Yes
setBigDecimal BigDecimal No
setBinaryFloat float or oracle.sql.BINARY_FLOAT Yes
setBinaryDouble double or oracle.sql.BINARY_DOUBLE Yes
setBinaryStream (see Notes section) java.io.InputStream No
setBlob java.sql.Blob No
setBLOB oracle.sql.BLOB Yes
setBoolean boolean No
setByte byte No
setBytes byte[] No
setCHAR (also see setFixedCHAR method) oracle.sql.CHAR Yes
setCharacterStream (see Notes section ) java.io.Reader No
setClob java.sql.Clob No
setCLOB oracle.sql.CLOB Yes
setDate (see Notes section ) java.sql.Date No
setDATE oracle.sql.DATE Yes
setDouble double No
setFixedCHAR (see setFixedCHAR section) java.lang.String Yes
setFloat float No
setInt int No
setINTERVALDS oracle.sql.INTERVALDS Yes
setINTERVALYM oracle.sql.INTERVALYM Yes
setLong long No
setNUMBER oracle.sql.NUMBER Yes
setRAW oracle.sql.RAW Yes
setRef java.sql.Ref No
setREF oracle.sql.REF Yes
setROWID oracle.sql.ROWID Yes
setShort short No
setString String No
setSTRUCT oracle.sql.STRUCT Yes
setTime java.sql.Time No
setTimestamp java.sql.Timestamp No
setTIMESTAMP oracle.sql.TIMESTAMP Yes
setTIMESTAMPTZ oracle.sql.TIMESTAMPTZ Yes
setTIMESTAMPLTZ oracle.sql.TIMESTAMPLTZ Yes
setUnicodeStream java.io.InputStream No
setURL java.net.URL No

13.4.7.2 Setter Method Size Limitations

Table 13-5 lists size limitations for the setBytes and setString methods for SQL binds.


Note:

These limitations do not apply to PL/SQL binds.

Table 13-5 Size Limitations for setBytes and setString Methods

Method Name Size Limit
setBytes 2000 bytes
setString 4000 bytes


See Also:

"Using Streams to Avoid Limits on setBytes and setString", for information about how to work around these limits using the stream application programming interface (API).

13.4.7.3 Setter Methods That Take Additional Input

The following setXXX methods take an additional input parameter other than the parameter index and the data item itself:

  • setAsciiStream(int paramIndex, InputStream istream, int length)

    Takes the length of the stream, in bytes.

  • setBinaryStream(int paramIndex, InputStream istream, int length)

    Takes the length of the stream, in bytes.

  • setCharacterStream(int paramIndex, Reader reader, int length)

    Takes the length of the stream, in characters.

  • setUnicodeStream(int paramIndex, InputStream istream, int length)

    Takes the length of the stream, in bytes.

The particular usefulness of the setCharacterStream method is that when a very large Unicode value is input to a LONGVARCHAR parameter, it can be more practical to send it through a java.io.Reader object. JDBC will read the data from the stream as needed, until it reaches the end-of-file mark. The JDBC driver will do any necessary conversion from Unicode to the database character format.


Note:

The preceding stream methods can also be used for large objects (LOBs). Refer to "Reading and Writing BLOB and CLOB Data" for more information.

Some of the other methods that take an additional parameter other than the parameter index and the data item itself are:

  • setDate(int paramIndex, Date x, Calendar cal)

  • setTime(int paramIndex, Time x, Calendar cal)

  • setTimestamp(int paramIndex, Timestamp x, Calendar cal)

13.4.7.4 Method setFixedCHAR for Binding CHAR Data into WHERE Clauses

CHAR data in the database is padded to the column width. This leads to a limitation in using the setCHAR method to bind character data into the WHERE clause of a SELECT statement. The character data in the WHERE clause must also be padded to the column width to produce a match in the SELECT statement. This is especially troublesome if you do not know the column width.

To remedy this, Oracle has added the setFixedCHAR method to the OraclePreparedStatement class. This method runs a non-padded comparison.


Note:

  • Remember to cast your prepared statement object to OraclePreparedStatement to use the setFixedCHAR method.

  • There is no need to use setFixedCHAR for an INSERT statement. The database always automatically pads the data to the column width as it inserts it.


Example

The following example demonstrates the difference between the setCHAR and setFixedCHAR methods.

/* Schema is :
 create table my_table (col1 char(10));
 insert into my_table values ('JDBC');
*/
 PreparedStatement pstmt = conn.prepareStatement 
                    ("select count(*) from my_table where col1 = ?");

 pstmt.setString (1, "JDBC");  // Set the Bind Value
 runQuery (pstmt);             // This will print " No of rows are 0"

 CHAR ch = new CHAR("JDBC      ", null);
 ((OraclePreparedStatement)pstmt).setCHAR(1, ch); // Pad it to 10 bytes
 runQuery (pstmt);             // This will print "No of rows are 1"

 ((OraclePreparedStatement)pstmt).setFixedCHAR(1, "JDBC");
  runQuery (pstmt);            // This will print "No of rows are 1"
 
 void runQuery (PreparedStatement ps)
 {    
   // Run the Query
   ResultSet rs = pstmt.executeQuery ();

   while (rs.next())
     System.out.println("No of rows are " + rs.getInt(1));
   
   rs.close();
   rs = null;
 }

13.5 Using Result Set Meta Data Extensions

The oracle.jdbc.OracleResultSetMetaData interface is JDBC 2.0-compliant but does not implement the getSchemaName and getTableName methods because Oracle Database 10g does not make this feasible. Oracle does implement many methods to retrieve information about an Oracle result set, however.

Key methods include the following:

The following example uses several of the methods in the OracleResultSetMetadata interface to retrieve the number of columns from the EMP table and the numerical type and SQL type name of each column:

DatabaseMetaData dbmd = conn.getMetaData();
ResultSet rset = dbmd.getTables("", "SCOTT", "EMP", null);

 while (rset.next())
 {
   OracleResultSetMetaData orsmd = ((OracleResultSet)rset).getMetaData();
   int numColumns = orsmd.getColumnCount();
   System.out.println("Num of columns = " + numColumns);

   for (int i=0; i<numColumns; i++)
   {
     System.out.print ("Column Name=" + orsmd.getColumnName (i+1));
     System.out.print (" Type=" + orsmd.getColumnType (i + 1) );
     System.out.println (" Type Name=" + orsmd.getColumnTypeName (i + 1));
  }
}

The program returns the following output:

Num of columns = 5
Column Name=TABLE_CAT Type=12 Type Name=VARCHAR2
Column Name=TABLE_SCHEM Type=12 Type Name=VARCHAR2
Column Name=TABLE_NAME Type=12 Type Name=VARCHAR2
Column Name=TABLE_TYPE Type=12 Type Name=VARCHAR2
Column Name=TABLE_REMARKS Type=12 Type Name=VARCHAR2