The Java Tutorials have been written for JDK 8. Examples and practices described in this page don't take advantage of improvements introduced in later releases and might use technology no longer available.
See Java Language Changes for a summary of updated language features in Java SE 9 and subsequent releases.
See JDK Release Notes for information about new features, enhancements, and removed or deprecated options for all JDK releases.
Note: MySQL and Java DB currently do not support the ARRAY
SQL data type. Consequently, no JDBC tutorial example is available to demonstrate the Array
JDBC data type.
The following topics are covered:
Use the method Connection.createArrayOf
to create Array
objects.
For example, suppose your database contains a table named REGIONS
, which has been created and populated with the following SQL statements; note that the syntax of these statements will vary depending on your database:
create table REGIONS (REGION_NAME varchar(32) NOT NULL, ZIPS varchar32 ARRAY[10] NOT NULL, PRIMARY KEY (REGION_NAME)); insert into REGIONS values( 'Northwest', '{"93101", "97201", "99210"}'); insert into REGIONS values( 'Southwest', '{"94105", "90049", "92027"}');
Connection con = DriverManager.getConnection(url, props); String [] northEastRegion = { "10022", "02110", "07399" }; Array anArray = con.createArrayOf("VARCHAR", northEastRegion);
The Oracle Database JDBC driver implements the java.sql.Array
interface with the oracle.sql.ARRAY
class.
As with the JDBC 4.0 large object interfaces (Blob
, Clob
, NClob
), you can manipulate Array
objects without having to bring all of their data from the database server to your client computer. An Array
object materializes the SQL ARRAY
it represents as either a result set or a Java array.
The following excerpt retrieves the SQL ARRAY
value in the column ZIPS
and assigns it to the java.sql.Array
object z
object. The excerpt retrieves the contents of z
and stores it in zips
, a Java array that contains objects of type String
. The excerpt iterates through the zips
array and checks that each postal (zip) code is valid. This code assumes that the class ZipCode
has been defined previously with the method isValid
returning true
if the given zip code matches one of the zip codes in a master list of valid zip codes:
ResultSet rs = stmt.executeQuery( "SELECT region_name, zips FROM REGIONS"); while (rs.next()) { Array z = rs.getArray("ZIPS"); String[] zips = (String[])z.getArray(); for (int i = 0; i < zips.length; i++) { if (!ZipCode.isValid(zips[i])) { // ... // Code to display warning } } }
In the following statement, the ResultSet
method getArray
returns the value stored in the column ZIPS
of the current row as the java.sql.Array
object z
:
Array z = rs.getArray("ZIPS");
The variable z
contains a locator, which is a logical pointer to the SQL ARRAY
on the server; it does not contain the elements of the ARRAY
itself. Being a logical pointer, z
can be used to manipulate the array on the server.
In the following line, getArray
is the Array.getArray
method, not the ResultSet.getArray
method used in the previous line. Because the Array.getArray
method returns an Object
in the Java programming language and because each zip code is a String
object, the result is cast to an array of String
objects before being assigned to the variable zips
.
String[] zips = (String[])z.getArray();
The Array.getArray
method materializes the SQL ARRAY
elements on the client as an array of String
objects. Because, in effect, the variable zips
contains the elements of the array, it is possible to iterate through zips
in a for
loop, looking for zip codes that are not valid.
Use the methods PreparedStatement.setArray
and PreparedStatement.setObject
to pass an Array
value as an input parameter to a PreparedStatement
object.
The following example sets the Array
object anArray
(created in a previous example) as the second parameter to the PreparedStatement pstmt
:
PreparedStatement pstmt = con.prepareStatement( "insert into REGIONS (region_name, zips) " + "VALUES (?, ?)"); pstmt.setString(1, "NorthEast"); pstmt.setArray(2, anArray); pstmt.executeUpdate();
Similarly, use the methods PreparedStatement.updateArray
and PreparedStatement.updateObject
to update a column in a table with an Array
value.
Array
objects remain valid for at least the duration of the transaction in which they are created. This could potentially result in an application running out of resources during a long running transaction. Applications may release Array
resources by invoking their free
method.
In the following excerpt, the method Array.free
is called to release the resources held for a previously created Array
object.
Array aArray = con.createArrayOf("VARCHAR", northEastRegionnewYork); // ... aArray.free();