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<chapter id="jdbc">

Any time you want to issue <acronym>SQL</acronym> statements to

the database, you require a <classname>Statement</classname> or

<classname>PreparedStatement</classname> instance. Once you have

a <classname>Statement</classname> or <classname>PreparedStatement

</classname>, you

can use issue a

a <classname>Statement</classname> or

<classname>PreparedStatement</classname>, you can use issue a

query. This will return a <classname>ResultSet</classname>

instance, which contains the entire result. <xref

linkend="jdbc-query-example"> illustrates this process.

</para>

<para>

This example willissues the same query as before using

This example willissue the same query as before using

a <classname>PreparedStatement</classname>

and a bind value in the query.

<programlisting>

<para>

The following must be considered when using the

<classname>Statement</classname> interface:

<classname>Statement</classname> or

<classname>PreparedStatement</classname> interface:

<itemizedlist>

<listitem>

open the connection and use it for the connection's

lifetime. But you have to remember that only one

<classname>ResultSet</classname> can exist per

<classname>Statement</classname> at a given time.

<classname>Statement</classname> or

<classname>PreparedStatement</classname> at a given time.

</para>

</listitem>

<listitem>

<para>

When you are done using the <classname>Statement</classname>

you should close the <classname>Statement</classname>.

or <classname>PreparedStatement</classname>

you should close it.

</para>

</listitem>

</itemizedlist>

update, or delete statement.

</para>

<example id="jdbc-delete-example">

<title>Simple Delete Example</title>

<para>

This example will issue a simple delete and print out the number

of rows deleted.

st.close();

</programlisting>

</para>

</example>

</sect1>

<sect1 id="jdbc-ddl">

however it doesn't return a result.

</para>

<example id="jdbc-drop-table-example">

<title>Drop Table Example</title>

<para>

This example will drop a table.

<programlisting>

st.close();

</programlisting>

</para>

</example>

</sect1>

<sect1 id="jdbc-binary-data">

<title>Storing Binary Data</title>

<para>

<application>PostgreSQL</application> provides two distinctway to

<application>PostgreSQL</application> provides two distinctways to

store binary data. Binary data can be stored in a table using

<application>PostgreSQL's</application> binary datatype

<type>bytea</type>, or by using the <firstterm>Large Object</firstterm>

feature which stores the binary data in a separate table in a special

format, and refers to from your own tables by an <type>OID</type> value.

format, and refers to that table by storing a value of type

<type>OID</type> in your table.

</para>

<para>

</para>

<para>

7.2 is the first releasethat the <acronym>JDBC</acronym> Driver

supports the <type>bytea</type> datatype. The introduction of

7.2 is the first releaseof the <acronym>JDBC</acronym> Driver

thatsupports the <type>bytea</type> datatype. The introduction of

this functionality in 7.2 has introduced a change in behavior

as compared to previous releases. In 7.2 the methods

<function>getBytes()</function>, <function>setBytes()</function>,

</para>

<para>

Hereyou can see howtheLarge Object is retrieved as an

Here thebinary data was retrieved as an

<classname>byte[]</classname>. You could have used a

<classname>InputStream</classname> object instead.

</para>

<programlisting>

// All LargeObject API calls must be within a transaction

conn.setAutoCommit(false);

// Get the Large Object Manager to perform operations with

LargeObjectManager lobj = ((org.postgresql.Connection)conn).getLargeObjectAPI();

//create a new large object

<programlisting>

// All LargeObject API calls must be within a transaction

conn.setAutoCommit(false);

// Get the Large Object Manager to perform operations with

LargeObjectManager lobj = ((org.postgresql.Connection)conn).getLargeObjectAPI();

PreparedStatement ps = con.prepareStatement("SELECT imgOID FROM imagesLO WHERE imgname=?");

byte buf[] = new byte[obj.size()];

obj.read(buf, 0, obj.size());

//do something with the data read here

// Close the object

obj.close();

}