Java Database Connectivity

Functionality

Since JDBC is mostly a collection of interface definitions and specifications, it allows multiple implementations of these interfaces to exist and be used by the same application at runtime. The API provides a mechanism for dynamically loading the correct Java packages and registering them with the JDBC Driver Manager (java.sql.DriverManager). java.sql.DriverManager is used as a java.sql.Connection factory for creating JDBC connections.

JDBC connections support creating and executing statements. JDBC connections support update statements such as SQL's CREATE, INSERT, UPDATE and DELETE, or query statements such as SELECT. Additionally, stored procedures may be invoked through a JDBC connection. JDBC represents statements using one of the following classes:

• Statement – the java.sql.Statement is sent to the database server each and every time. In other words, the java.sql.Statement methods are executed using SQL statements to obtain a java.sql.ResultSet object containing the data.
• PreparedStatement – java.sql.PreparedStatement is a subinterface of the java.sql.Statement interface. The statement is cached and then the execution path is pre-determined on the database server, allowing it to be executed multiple times in an efficient manner. java.sql.PreparedStatement is used to execute pre-compiled SQL statements. Running pre-compiled statements increases statement execution efficiency and performance. The java.sql.PreparedStatement is often used for dynamic statement where some input parameters must be passed into the target database. The java.sql.PreparedStatement allows the dynamic query to vary depending on the query parameter.
• CallableStatement – java.sql.CallableStatement is a subinterface of the java.sql.Statement interface. It is used for executing stored procedures on the database. Both input and output parameters must be passed into the database for stored procedures.

Update statements such as INSERT, UPDATE and DELETE return an update count indicating the number of rows affected in the database as an integer. These statements do not return any other information.

Query statements return a JDBC row result set. The row result set is used to walk over the result set. Individual columns in a row are retrieved either by name or by column number. There may be any number of rows in the result set. The row result set has metadata that describes the names of the columns and their types.

There is an extension to the basic JDBC API in the javax.sql.

JDBC connections are often managed via a connection pool rather than obtained directly from the driver, like javax.sql.DataSource.

Examples

When a Java application needs a database connection, one of the DriverManager.getConnection() methods is used to create a JDBC java.sql.Connection. The URL used is dependent upon the particular database and JDBC driver. It will always begin with the jdbc: protocol, but the rest is up to the particular vendor.

<span id="mwATk"></span><span class="kn" id="mwATo">import</span><span class="w" id="mwATs"> </span><span class="nn" id="mwATw">java.sql.Connection</span><span class="p" id="mwAT0">;</span> <span class="kn" id="mwAT4">import</span><span class="w" id="mwAT8"> </span><span class="nn" id="mwAUA">java.sql.DriverManager</span><span class="p" id="mwAUE">;</span> <span class="kn" id="mwAUI">import</span><span class="w" id="mwAUM"> </span><span class="nn" id="mwAUQ">java.sql.SQLException</span><span class="p" id="mwAUU">;</span> <span class="n" id="mwAUY">Connection</span><span class="w" id="mwAUc"> </span><span class="n" id="mwAUg">conn</span><span class="w" id="mwAUk"> </span><span class="o" id="mwAUo">=</span><span class="w" id="mwAUs"> </span><span class="n" id="mwAUw">DriverManager</span><span class="p" id="mwAU0">.</span><span class="na" id="mwAU4">getConnection</span><span class="p" id="mwAU8">(</span> <span class="w" id="mwAVA"> </span><span class="s" id="mwAVE">"jdbc:somejdbcvendor:other data needed by some jdbc vendor"</span><span class="p" id="mwAVI">,</span> <span class="w" id="mwAVM"> </span><span class="s" id="mwAVQ">"myLogin"</span><span class="p" id="mwAVU">,</span> <span class="w" id="mwAVY"> </span><span class="s" id="mwAVc">"myPassword"</span> <span class="p" id="mwAVg">);</span> <span class="k" id="mwAVk">try</span><span class="w" id="mwAVo"> </span><span class="p" id="mwAVs">{</span> <span class="w" id="mwAVw"> </span><span class="c1" id="mwAV0">// use the connection here</span> <span class="p" id="mwAV4">}</span><span class="w" id="mwAV8"> </span><span class="k" id="mwAWA">finally</span><span class="w" id="mwAWE"> </span><span class="p" id="mwAWI">{</span> <span class="w" id="mwAWM"> </span><span class="k" id="mwAWQ">try</span><span class="w" id="mwAWU"> </span><span class="p" id="mwAWY">{</span><span class="w" id="mwAWc"> </span> <span class="w" id="mwAWg"> </span><span class="c1" id="mwAWk">// close the connection after we are done</span> <span class="w" id="mwAWo"> </span><span class="n" id="mwAWs">conn</span><span class="p" id="mwAWw">.</span><span class="na" id="mwAW0">close</span><span class="p" id="mwAW4">();</span> <span class="w" id="mwAW8"> </span><span class="p" id="mwAXA">}</span><span class="w" id="mwAXE"> </span><span class="k" id="mwAXI">catch</span><span class="w" id="mwAXM"> </span><span class="p" id="mwAXQ">(</span><span class="n" id="mwAXU">SQLException</span><span class="w" id="mwAXY"> </span><span class="n" id="mwAXc">e</span><span class="p" id="mwAXg">)</span><span class="w" id="mwAXk"> </span><span class="p" id="mwAXo">{</span> <span class="w" id="mwAXs"> </span><span class="c1" id="mwAXw">// propagate the original exception, not the one caught here</span> <span class="w" id="mwAX0"> </span><span class="n" id="mwAX4">logger</span><span class="p" id="mwAX8">.</span><span class="na" id="mwAYA">warn</span><span class="p" id="mwAYE">(</span><span class="s" id="mwAYI">"Could not close JDBC Connection"</span><span class="p" id="mwAYM">,</span><span class="w" id="mwAYQ"> </span><span class="n" id="mwAYU">e</span><span class="p" id="mwAYY">);</span> <span class="w" id="mwAYc"> </span><span class="p" id="mwAYg">}</span> <span class="p" id="mwAYk">}</span>

Starting from Java SE 7, one can use Java's try-with-resources statement to simplify the above code:

<span id="mwAY4"></span><span class="kn" id="mwAY8">import</span><span class="w" id="mwAZA"> </span><span class="nn" id="mwAZE">java.sql.Connection</span><span class="p" id="mwAZI">;</span> <span class="kn" id="mwAZM">import</span><span class="w" id="mwAZQ"> </span><span class="nn" id="mwAZU">java.sql.DriverManager</span><span class="p" id="mwAZY">;</span> <span class="k" id="mwAZc">try</span><span class="w" id="mwAZg"> </span><span class="p" id="mwAZk">(</span><span class="n" id="mwAZo">Connection</span><span class="w" id="mwAZs"> </span><span class="n" id="mwAZw">conn</span><span class="w" id="mwAZ0"> </span><span class="o" id="mwAZ4">=</span><span class="w" id="mwAZ8"> </span><span class="n" id="mwAaA">DriverManager</span><span class="p" id="mwAaE">.</span><span class="na" id="mwAaI">getConnection</span><span class="p" id="mwAaM">(</span> <span class="w" id="mwAaQ"> </span><span class="s" id="mwAaU">"jdbc:somejdbcvendor:other data needed by some jdbc vendor"</span><span class="p" id="mwAaY">,</span> <span class="w" id="mwAac"> </span><span class="s" id="mwAag">"myLogin"</span><span class="p" id="mwAak">,</span> <span class="w" id="mwAao"> </span><span class="s" id="mwAas">"myPassword"</span><span class="p" id="mwAaw">))</span><span class="w" id="mwAa0"> </span><span class="p" id="mwAa4">{</span> <span class="w" id="mwAa8"> </span><span class="c1" id="mwAbA">// use the connection here</span> <span class="p" id="mwAbE">}</span> <span class="c1" id="mwAbI">// conn.close() automatically called</span> <span class="c1" id="mwAbM">// the connection will automatically close after leaving the try block</span>

Once a connection is established, a java.sql.Statement can be created.

<span id="mwAbg"></span><span class="kn" id="mwAbk">import</span><span class="w" id="mwAbo"> </span><span class="nn" id="mwAbs">java.sql.Statement</span><span class="p" id="mwAbw">;</span> <span class="k" id="mwAb0">try</span><span class="w" id="mwAb4"> </span><span class="p" id="mwAb8">(</span><span class="n" id="mwAcA">Statement</span><span class="w" id="mwAcE"> </span><span class="n" id="mwAcI">stmt</span><span class="w" id="mwAcM"> </span><span class="o" id="mwAcQ">=</span><span class="w" id="mwAcU"> </span><span class="n" id="mwAcY">conn</span><span class="p" id="mwAcc">.</span><span class="na" id="mwAcg">createStatement</span><span class="p" id="mwAck">())</span><span class="w" id="mwAco"> </span><span class="p" id="mwAcs">{</span> <span class="w" id="mwAcw"> </span><span class="n" id="mwAc0">stmt</span><span class="p" id="mwAc4">.</span><span class="na" id="mwAc8">executeUpdate</span><span class="p" id="mwAdA">(</span><span class="s" id="mwAdE">"INSERT INTO MyTable(name) VALUES ('my name')"</span><span class="p" id="mwAdI">);</span> <span class="p" id="mwAdM">}</span>

Note that java.sql.Connections, java.sql.Statements, and java.sql.ResultSets often tie up operating system resources such as sockets or file descriptors. In the case of java.sql.Connections to remote database servers, further resources are tied up on the server, e.g. cursors for currently open java.sql.ResultSets. It is vital to close() any JDBC object as soon as it has played its part; garbage collection should not be relied upon. The above try-with-resources construct is a code pattern that obviates this.

Data is retrieved from the database using a database query mechanism. The example below shows creating a statement and executing a query.

<span id="mwAeI"></span><span class="kn" id="mwAeM">import</span><span class="w" id="mwAeQ"> </span><span class="nn" id="mwAeU">java.sql.ResultSet</span><span class="p" id="mwAeY">;</span> <span class="kn" id="mwAec">import</span><span class="w" id="mwAeg"> </span><span class="nn" id="mwAek">java.sql.Statement</span><span class="p" id="mwAeo">;</span> <span class="k" id="mwAes">try</span><span class="w" id="mwAew"> </span><span class="p" id="mwAe0">(</span><span class="n" id="mwAe4">Statement</span><span class="w" id="mwAe8"> </span><span class="n" id="mwAfA">stmt</span><span class="w" id="mwAfE"> </span><span class="o" id="mwAfI">=</span><span class="w" id="mwAfM"> </span><span class="n" id="mwAfQ">conn</span><span class="p" id="mwAfU">.</span><span class="na" id="mwAfY">createStatement</span><span class="p" id="mwAfc">();</span> <span class="w" id="mwAfg"> </span><span class="n" id="mwAfk">ResultSet</span><span class="w" id="mwAfo"> </span><span class="n" id="mwAfs">rs</span><span class="w" id="mwAfw"> </span><span class="o" id="mwAf0">=</span><span class="w" id="mwAf4"> </span><span class="n" id="mwAf8">stmt</span><span class="p" id="mwAgA">.</span><span class="na" id="mwAgE">executeQuery</span><span class="p" id="mwAgI">(</span><span class="s" id="mwAgM">"SELECT * FROM MyTable"</span><span class="p" id="mwAgQ">)</span> <span class="p" id="mwAgU">)</span><span class="w" id="mwAgY"> </span><span class="p" id="mwAgc">{</span> <span class="w" id="mwAgg"> </span><span class="k" id="mwAgk">while</span><span class="w" id="mwAgo"> </span><span class="p" id="mwAgs">(</span><span class="n" id="mwAgw">rs</span><span class="p" id="mwAg0">.</span><span class="na" id="mwAg4">next</span><span class="p" id="mwAg8">())</span><span class="w" id="mwAhA"> </span><span class="p" id="mwAhE">{</span> <span class="w" id="mwAhI"> </span><span class="kt" id="mwAhM">int</span><span class="w" id="mwAhQ"> </span><span class="n" id="mwAhU">numColumns</span><span class="w" id="mwAhY"> </span><span class="o" id="mwAhc">=</span><span class="w" id="mwAhg"> </span><span class="n" id="mwAhk">rs</span><span class="p" id="mwAho">.</span><span class="na" id="mwAhs">getMetaData</span><span class="p" id="mwAhw">().</span><span class="na" id="mwAh0">getColumnCount</span><span class="p" id="mwAh4">();</span> <span class="w" id="mwAh8"> </span><span class="k" id="mwAiA">for</span><span class="w" id="mwAiE"> </span><span class="p" id="mwAiI">(</span><span class="kt" id="mwAiM">int</span><span class="w" id="mwAiQ"> </span><span class="n" id="mwAiU">i</span><span class="w" id="mwAiY"> </span><span class="o" id="mwAic">=</span><span class="w" id="mwAig"> </span><span class="mi" id="mwAik">1</span><span class="p" id="mwAio">;</span><span class="w" id="mwAis"> </span><span class="n" id="mwAiw">i</span><span class="w" id="mwAi0"> </span><span class="o" id="mwAi4"><=</span><span class="w" id="mwAi8"> </span><span class="n" id="mwAjA">numColumns</span><span class="p" id="mwAjE">;</span><span class="w" id="mwAjI"> </span><span class="n" id="mwAjM">i</span><span class="o" id="mwAjQ">++</span><span class="p" id="mwAjU">)</span><span class="w" id="mwAjY"> </span><span class="p" id="mwAjc">{</span> <span class="w" id="mwAjg"> </span><span class="c1" id="mwAjk">// Column numbers start at 1.</span> <span class="w" id="mwAjo"> </span><span class="c1" id="mwAjs">// Also, there are many methods on the result set to return</span> <span class="w" id="mwAjw"> </span><span class="c1" id="mwAj0">// the column as a particular type. Refer to the Sun documentation</span> <span class="w" id="mwAj4"> </span><span class="c1" id="mwAj8">// for the list of valid conversions.</span> <span class="w" id="mwAkA"> </span><span class="n" id="mwAkE">System</span><span class="p" id="mwAkI">.</span><span class="na" id="mwAkM">out</span><span class="p" id="mwAkQ">.</span><span class="na" id="mwAkU">printf</span><span class="p" id="mwAkY">(</span><span class="s" id="mwAkc">"COLUMN %d = %s%n"</span><span class="p" id="mwAkg">,</span><span class="w" id="mwAkk"> </span><span class="n" id="mwAko">i</span><span class="p" id="mwAks">,</span><span class="w" id="mwAkw"> </span><span class="n" id="mwAk0">rs</span><span class="p" id="mwAk4">.</span><span class="na" id="mwAk8">getObject</span><span class="p" id="mwAlA">(</span><span class="n" id="mwAlE">i</span><span class="p" id="mwAlI">));</span> <span class="w" id="mwAlM"> </span><span class="p" id="mwAlQ">}</span> <span class="w" id="mwAlU"> </span><span class="p" id="mwAlY">}</span> <span class="p" id="mwAlc">}</span>

The following code is an example of a java.sql.PreparedStatement query which uses conn and class from the first example:

<span id="mwAl0"></span><span class="kn" id="mwAl4">import</span><span class="w" id="mwAl8"> </span><span class="nn" id="mwAmA">java.sql.PreparedStatement</span><span class="p" id="mwAmE">;</span> <span class="kn" id="mwAmI">import</span><span class="w" id="mwAmM"> </span><span class="nn" id="mwAmQ">java.sql.ResultSet</span><span class="p" id="mwAmU">;</span> <span class="k" id="mwAmY">try</span><span class="w" id="mwAmc"> </span><span class="p" id="mwAmg">(</span><span class="n" id="mwAmk">PreparedStatement</span><span class="w" id="mwAmo"> </span><span class="n" id="mwAms">ps</span><span class="w" id="mwAmw"> </span><span class="o" id="mwAm0">=</span> <span class="w" id="mwAm4"> </span><span class="n" id="mwAm8">conn</span><span class="p" id="mwAnA">.</span><span class="na" id="mwAnE">prepareStatement</span><span class="p" id="mwAnI">(</span><span class="s" id="mwAnM">"SELECT i.*, j.* FROM Omega i, Zappa j WHERE i.name = ? AND j.num = ?"</span><span class="p" id="mwAnQ">)</span> <span class="p" id="mwAnU">)</span><span class="w" id="mwAnY"> </span><span class="p" id="mwAnc">{</span> <span class="w" id="mwAng"> </span><span class="c1" id="mwAnk">// In the SQL statement being prepared, each question mark is a placeholder</span> <span class="w" id="mwAno"> </span><span class="c1" id="mwAns">// that must be replaced with a value you provide through a "set" method invocation.</span> <span class="w" id="mwAnw"> </span><span class="c1" id="mwAn0">// The following two method calls replace the two placeholders; the first is</span> <span class="w" id="mwAn4"> </span><span class="c1" id="mwAn8">// replaced by a string value, and the second by an integer value.</span> <span class="w" id="mwAoA"> </span><span class="n" id="mwAoE">ps</span><span class="p" id="mwAoI">.</span><span class="na" id="mwAoM">setString</span><span class="p" id="mwAoQ">(</span><span class="mi" id="mwAoU">1</span><span class="p" id="mwAoY">,</span><span class="w" id="mwAoc"> </span><span class="s" id="mwAog">"Poor Yorick"</span><span class="p" id="mwAok">);</span> <span class="w" id="mwAoo"> </span><span class="n" id="mwAos">ps</span><span class="p" id="mwAow">.</span><span class="na" id="mwAo0">setInt</span><span class="p" id="mwAo4">(</span><span class="mi" id="mwAo8">2</span><span class="p" id="mwApA">,</span><span class="w" id="mwApE"> </span><span class="mi" id="mwApI">8008</span><span class="p" id="mwApM">);</span> <span class="w" id="mwApQ"> </span><span class="c1" id="mwApU">// The ResultSet, rs, conveys the result of executing the SQL statement.</span> <span class="w" id="mwApY"> </span><span class="c1" id="mwApc">// Each time you call rs.next(), an internal row pointer, or cursor,</span> <span class="w" id="mwApg"> </span><span class="c1" id="mwApk">// is advanced to the next row of the result. The cursor initially is</span> <span class="w" id="mwApo"> </span><span class="c1" id="mwAps">// positioned before the first row.</span> <span class="w" id="mwApw"> </span><span class="k" id="mwAp0">try</span><span class="w" id="mwAp4"> </span><span class="p" id="mwAp8">(</span><span class="n" id="mwAqA">ResultSet</span><span class="w" id="mwAqE"> </span><span class="n" id="mwAqI">rs</span><span class="w" id="mwAqM"> </span><span class="o" id="mwAqQ">=</span><span class="w" id="mwAqU"> </span><span class="n" id="mwAqY">ps</span><span class="p" id="mwAqc">.</span><span class="na" id="mwAqg">executeQuery</span><span class="p" id="mwAqk">())</span><span class="w" id="mwAqo"> </span><span class="p" id="mwAqs">{</span> <span class="w" id="mwAqw"> </span><span class="k" id="mwAq0">while</span><span class="w" id="mwAq4"> </span><span class="p" id="mwAq8">(</span><span class="n" id="mwArA">rs</span><span class="p" id="mwArE">.</span><span class="na" id="mwArI">next</span><span class="p" id="mwArM">())</span><span class="w" id="mwArQ"> </span><span class="p" id="mwArU">{</span> <span class="w" id="mwArY"> </span><span class="k" id="mwArc">for</span><span class="w" id="mwArg"> </span><span class="p" id="mwArk">(</span><span class="kt" id="mwAro">int</span><span class="w" id="mwArs"> </span><span class="n" id="mwArw">i</span><span class="w" id="mwAr0"> </span><span class="o" id="mwAr4">=</span><span class="w" id="mwAr8"> </span><span class="mi" id="mwAsA">1</span><span class="p" id="mwAsE">;</span><span class="w" id="mwAsI"> </span><span class="n" id="mwAsM">i</span><span class="w" id="mwAsQ"> </span><span class="o" id="mwAsU"><=</span><span class="w" id="mwAsY"> </span><span class="n" id="mwAsc">rs</span><span class="p" id="mwAsg">.</span><span class="na" id="mwAsk">getMetaData</span><span class="p" id="mwAso">().</span><span class="na" id="mwAss">getColumnCount</span><span class="p" id="mwAsw">();</span><span class="w" id="mwAs0"> </span><span class="n" id="mwAs4">i</span><span class="o" id="mwAs8">++</span><span class="p" id="mwAtA">)</span><span class="w" id="mwAtE"> </span><span class="p" id="mwAtI">{</span> <span class="w" id="mwAtM"> </span><span class="c1" id="mwAtQ">// Column numbers start at 1.</span> <span class="w" id="mwAtU"> </span><span class="c1" id="mwAtY">// Also, there are many methods on the result set to return</span> <span class="w" id="mwAtc"> </span><span class="c1" id="mwAtg">// the column as a particular type. Refer to the Sun documentation</span> <span class="w" id="mwAtk"> </span><span class="c1" id="mwAto">// for the list of valid conversions.</span> <span class="w" id="mwAts"> </span><span class="n" id="mwAtw">System</span><span class="p" id="mwAt0">.</span><span class="na" id="mwAt4">out</span><span class="p" id="mwAt8">.</span><span class="na" id="mwAuA">printf</span><span class="p" id="mwAuE">(</span><span class="s" id="mwAuI">"COLUMN %d = %s%n"</span><span class="p" id="mwAuM">,</span><span class="w" id="mwAuQ"> </span><span class="n" id="mwAuU">i</span><span class="p" id="mwAuY">,</span><span class="w" id="mwAuc"> </span><span class="n" id="mwAug">rs</span><span class="p" id="mwAuk">.</span><span class="na" id="mwAuo">getObject</span><span class="p" id="mwAus">(</span><span class="n" id="mwAuw">i</span><span class="p" id="mwAu0">));</span> <span class="w" id="mwAu4"> </span><span class="p" id="mwAu8">}</span> <span class="w" id="mwAvA"> </span><span class="p" id="mwAvE">}</span> <span class="w" id="mwAvI"> </span><span class="p" id="mwAvM">}</span> <span class="p" id="mwAvQ">}</span>

If a database operation fails, JDBC raises an SQLException. There is typically very little one can do to recover from such an error, apart from logging it with as much detail as possible. It is recommended that the java.sql.SQLException be translated into an application domain exception (an unchecked one) that eventually results in a transaction rollback and a notification to the user.

The following code is an example of a database transaction:

<span id="mwAvw"></span><span class="kn" id="mwAv0">import</span><span class="w" id="mwAv4"> </span><span class="nn" id="mwAv8">java.sql.SQLException</span><span class="p" id="mwAwA">;</span> <span class="kt" id="mwAwE">boolean</span><span class="w" id="mwAwI"> </span><span class="n" id="mwAwM">autoCommitDefault</span><span class="w" id="mwAwQ"> </span><span class="o" id="mwAwU">=</span><span class="w" id="mwAwY"> </span><span class="n" id="mwAwc">conn</span><span class="p" id="mwAwg">.</span><span class="na" id="mwAwk">getAutoCommit</span><span class="p" id="mwAwo">();</span> <span class="k" id="mwAws">try</span><span class="w" id="mwAww"> </span><span class="p" id="mwAw0">{</span> <span class="w" id="mwAw4"> </span><span class="n" id="mwAw8">conn</span><span class="p" id="mwAxA">.</span><span class="na" id="mwAxE">setAutoCommit</span><span class="p" id="mwAxI">(</span><span class="kc" id="mwAxM">false</span><span class="p" id="mwAxQ">);</span> <span class="w" id="mwAxU"> </span><span class="c1" id="mwAxY">// Execute statements on conn here transactionally</span> <span class="w" id="mwAxc"> </span><span class="n" id="mwAxg">conn</span><span class="p" id="mwAxk">.</span><span class="na" id="mwAxo">commit</span><span class="p" id="mwAxs">();</span> <span class="p" id="mwAxw">}</span><span class="w" id="mwAx0"> </span><span class="k" id="mwAx4">catch</span><span class="w" id="mwAx8"> </span><span class="p" id="mwAyA">(</span><span class="n" id="mwAyE">SQLException</span><span class="w" id="mwAyI"> </span><span class="n" id="mwAyM">e</span><span class="p" id="mwAyQ">)</span><span class="w" id="mwAyU"> </span><span class="p" id="mwAyY">{</span> <span class="w" id="mwAyc"> </span><span class="k" id="mwAyg">try</span><span class="w" id="mwAyk"> </span><span class="p" id="mwAyo">{</span><span class="w" id="mwAys"> </span> <span class="w" id="mwAyw"> </span><span class="n" id="mwAy0">conn</span><span class="p" id="mwAy4">.</span><span class="na" id="mwAy8">rollback</span><span class="p" id="mwAzA">();</span><span class="w" id="mwAzE"> </span> <span class="w" id="mwAzI"> </span><span class="p" id="mwAzM">}</span><span class="w" id="mwAzQ"> </span><span class="k" id="mwAzU">catch</span><span class="w" id="mwAzY"> </span><span class="p" id="mwAzc">(</span><span class="n" id="mwAzg">Throwable</span><span class="w" id="mwAzk"> </span><span class="n" id="mwAzo">e</span><span class="p" id="mwAzs">)</span><span class="w" id="mwAzw"> </span><span class="p" id="mwAz0">{</span><span class="w" id="mwAz4"> </span> <span class="w" id="mwAz8"> </span><span class="n" id="mwA0A">logger</span><span class="p" id="mwA0E">.</span><span class="na" id="mwA0I">warn</span><span class="p" id="mwA0M">(</span><span class="s" id="mwA0Q">"Could not rollback transaction"</span><span class="p" id="mwA0U">,</span><span class="w" id="mwA0Y"> </span><span class="n" id="mwA0c">e</span><span class="p" id="mwA0g">);</span><span class="w" id="mwA0k"> </span> <span class="w" id="mwA0o"> </span><span class="p" id="mwA0s">}</span> <span class="w" id="mwA0w"> </span><span class="k" id="mwA00">throw</span><span class="w" id="mwA04"> </span><span class="n" id="mwA08">e</span><span class="p" id="mwA1A">;</span> <span class="p" id="mwA1E">}</span><span class="w" id="mwA1I"> </span><span class="k" id="mwA1M">finally</span><span class="w" id="mwA1Q"> </span><span class="p" id="mwA1U">{</span> <span class="w" id="mwA1Y"> </span><span class="k" id="mwA1c">try</span><span class="w" id="mwA1g"> </span><span class="p" id="mwA1k">{</span><span class="w" id="mwA1o"> </span> <span class="w" id="mwA1s"> </span><span class="n" id="mwA1w">conn</span><span class="p" id="mwA10">.</span><span class="na" id="mwA14">setAutoCommit</span><span class="p" id="mwA18">(</span><span class="n" id="mwA2A">autoCommitDefault</span><span class="p" id="mwA2E">);</span><span class="w" id="mwA2I"> </span> <span class="w" id="mwA2M"> </span><span class="p" id="mwA2Q">}</span><span class="w" id="mwA2U"> </span><span class="k" id="mwA2Y">catch</span><span class="w" id="mwA2c"> </span><span class="p" id="mwA2g">(</span><span class="n" id="mwA2k">Throwable</span><span class="w" id="mwA2o"> </span><span class="n" id="mwA2s">e</span><span class="p" id="mwA2w">)</span><span class="w" id="mwA20"> </span><span class="p" id="mwA24">{</span><span class="w" id="mwA28"> </span> <span class="w" id="mwA3A"> </span><span class="n" id="mwA3E">logger</span><span class="p" id="mwA3I">.</span><span class="na" id="mwA3M">warn</span><span class="p" id="mwA3Q">(</span><span class="s" id="mwA3U">"Could not restore AutoCommit setting"</span><span class="p" id="mwA3Y">,</span><span class="w" id="mwA3c"> </span><span class="n" id="mwA3g">e</span><span class="p" id="mwA3k">);</span><span class="w" id="mwA3o"> </span> <span class="w" id="mwA3s"> </span><span class="p" id="mwA3w">}</span> <span class="p" id="mwA30">}</span>

For an example of a java.sql.CallableStatement (to call stored procedures in the database), see the JDBC API Guide documentation.

<span id="mwA4M"></span><span class="kn" id="mwA4Q">package</span><span class="w" id="mwA4U"> </span><span class="nn" id="mwA4Y">org.wikipedia.examples</span><span class="p" id="mwA4c">;</span> <span class="kn" id="mwA4g">import</span><span class="w" id="mwA4k"> </span><span class="nn" id="mwA4o">java.sql.Connection</span><span class="p" id="mwA4s">;</span> <span class="kn" id="mwA4w">import</span><span class="w" id="mwA40"> </span><span class="nn" id="mwA44">java.sql.DriverManager</span><span class="p" id="mwA48">;</span> <span class="kn" id="mwA5A">import</span><span class="w" id="mwA5E"> </span><span class="nn" id="mwA5I">java.sql.Statement</span><span class="p" id="mwA5M">;</span> <span class="kd" id="mwA5Q">public</span><span class="w" id="mwA5U"> </span><span class="kd" id="mwA5Y">class</span> <span class="nc" id="mwA5c">DatabaseExample</span><span class="w" id="mwA5g"> </span><span class="p" id="mwA5k">{</span> <span class="w" id="mwA5o"> </span><span class="kd" id="mwA5s">private</span><span class="w" id="mwA5w"> </span><span class="kd" id="mwA50">static</span><span class="w" id="mwA54"> </span><span class="kd" id="mwA58">final</span><span class="w" id="mwA6A"> </span><span class="n" id="mwA6E">String</span><span class="w" id="mwA6I"> </span><span class="n" id="mwA6M">DB_URL</span><span class="w" id="mwA6Q"> </span><span class="o" id="mwA6U">=</span><span class="w" id="mwA6Y"> </span><span class="s" id="mwA6c">"jdbc:mysql://localhost/mydb"</span><span class="p" id="mwA6g">;</span> <span class="w" id="mwA6k"> </span><span class="kd" id="mwA6o">public</span><span class="w" id="mwA6s"> </span><span class="kd" id="mwA6w">static</span><span class="w" id="mwA60"> </span><span class="kt" id="mwA64">void</span><span class="w" id="mwA68"> </span><span class="nf" id="mwA7A">main</span><span class="p" id="mwA7E">(</span><span class="n" id="mwA7I">String</span><span class="o" id="mwA7M">[]</span><span class="w" id="mwA7Q"> </span><span class="n" id="mwA7U">args</span><span class="p" id="mwA7Y">)</span><span class="w" id="mwA7c"> </span><span class="p" id="mwA7g">{</span> <span class="w" id="mwA7k"> </span><span class="k" id="mwA7o">try</span><span class="w" id="mwA7s"> </span><span class="p" id="mwA7w">{</span> <span class="w" id="mwA70"> </span><span class="n" id="mwA74">Class</span><span class="p" id="mwA78">.</span><span class="na" id="mwA8A">forName</span><span class="p" id="mwA8E">(</span><span class="s" id="mwA8I">"com.mysql.jdbc.Driver"</span><span class="p" id="mwA8M">);</span> <span class="w" id="mwA8Q"> </span><span class="n" id="mwA8U">Connection</span><span class="w" id="mwA8Y"> </span><span class="n" id="mwA8c">conn</span><span class="w" id="mwA8g"> </span><span class="o" id="mwA8k">=</span><span class="w" id="mwA8o"> </span><span class="n" id="mwA8s">DriverManager</span><span class="p" id="mwA8w">.</span><span class="na" id="mwA80">getConnection</span><span class="p" id="mwA84">(</span><span class="n" id="mwA88">DB_URL</span><span class="p" id="mwA9A">,</span><span class="w" id="mwA9E"> </span><span class="s" id="mwA9I">"root"</span><span class="p" id="mwA9M">,</span><span class="w" id="mwA9Q"> </span><span class="s" id="mwA9U">"root"</span><span class="p" id="mwA9Y">);</span> <span class="w" id="mwA9c"> </span><span class="n" id="mwA9g">Statement</span><span class="w" id="mwA9k"> </span><span class="n" id="mwA9o">stmt</span><span class="w" id="mwA9s"> </span><span class="o" id="mwA9w">=</span><span class="w" id="mwA90"> </span><span class="n" id="mwA94">conn</span><span class="p" id="mwA98">.</span><span class="na" id="mwA-A">createStatement</span><span class="p" id="mwA-E">();</span> <span class="w" id="mwA-I"> </span> <span class="w" id="mwA-M"> </span><span class="n" id="mwA-Q">String</span><span class="w" id="mwA-U"> </span><span class="n" id="mwA-Y">sql</span><span class="w" id="mwA-c"> </span><span class="o" id="mwA-g">=</span><span class="w" id="mwA-k"> </span><span class="s" id="mwA-o">"INSERT INTO emp1 VALUES ('pctb5361', 'kiril', 'john', 968666668)"</span><span class="p" id="mwA-s">;</span> <span class="w" id="mwA-w"> </span><span class="n" id="mwA-0">stmt</span><span class="p" id="mwA-4">.</span><span class="na" id="mwA-8">executeUpdate</span><span class="p" id="mwA_A">(</span><span class="n" id="mwA_E">sql</span><span class="p" id="mwA_I">);</span> <span class="w" id="mwA_M"> </span> <span class="w" id="mwA_Q"> </span><span class="n" id="mwA_U">System</span><span class="p" id="mwA_Y">.</span><span class="na" id="mwA_c">out</span><span class="p" id="mwA_g">.</span><span class="na" id="mwA_k">println</span><span class="p" id="mwA_o">(</span><span class="s" id="mwA_s">"Inserted records into the table..."</span><span class="p" id="mwA_w">);</span> <span class="w" id="mwA_0"> </span><span class="p" id="mwA_4">}</span><span class="w" id="mwA_8"> </span><span class="k" id="mwBAA">catch</span><span class="w" id="mwBAE"> </span><span class="p" id="mwBAI">(</span><span class="n" id="mwBAM">SQLException</span><span class="w" id="mwBAQ"> </span><span class="n" id="mwBAU">e</span><span class="p" id="mwBAY">)</span><span class="w" id="mwBAc"> </span><span class="p" id="mwBAg">{</span> <span class="w" id="mwBAk"> </span><span class="n" id="mwBAo">System</span><span class="p" id="mwBAs">.</span><span class="na" id="mwBAw">err</span><span class="p" id="mwBA0">.</span><span class="na" id="mwBA4">printf</span><span class="p" id="mwBA8">(</span><span class="s" id="mwBBA">"A SQL error occurred: %s%n"</span><span class="p" id="mwBBE">,</span><span class="w" id="mwBBI"> </span><span class="n" id="mwBBM">e</span><span class="p" id="mwBBQ">.</span><span class="na" id="mwBBU">getMessage</span><span class="p" id="mwBBY">());</span> <span class="w" id="mwBBc"> </span><span class="p" id="mwBBg">}</span><span class="w" id="mwBBk"> </span><span class="k" id="mwBBo">catch</span><span class="w" id="mwBBs"> </span><span class="p" id="mwBBw">(</span><span class="n" id="mwBB0">Exception</span><span class="w" id="mwBB4"> </span><span class="n" id="mwBB8">e</span><span class="p" id="mwBCA">)</span><span class="w" id="mwBCE"> </span><span class="p" id="mwBCI">{</span> <span class="w" id="mwBCM"> </span><span class="n" id="mwBCQ">System</span><span class="p" id="mwBCU">.</span><span class="na" id="mwBCY">err</span><span class="p" id="mwBCc">.</span><span class="na" id="mwBCg">println</span><span class="p" id="mwBCk">(</span><span class="s" id="mwBCo">"An unknown error occurred."</span><span class="p" id="mwBCs">);</span> <span class="w" id="mwBCw"> </span><span class="n" id="mwBC0">e</span><span class="p" id="mwBC4">.</span><span class="na" id="mwBC8">printStackTrace</span><span class="p" id="mwBDA">();</span> <span class="w" id="mwBDE"> </span><span class="p" id="mwBDI">}</span> <span class="w" id="mwBDM"> </span><span class="p" id="mwBDQ">}</span> <span class="p" id="mwBDU">}</span>

JDBC drivers

JDBC drivers are client-side adapters (installed on the client machine, not on the server) that convert requests from Java programs to a protocol that the DBMS can understand.

Types

Commercial and free drivers provide connectivity to most relational-database servers. These drivers fall into one of the following types:

• Type 1 that calls native code of the locally available ODBC driver. (Note: In JDBC 4.2, JDBC-ODBC bridge has been removed)
• Type 2 that calls database vendor native library on a client side. This code then talks to database over the network.
• Type 3, the pure-java driver that talks with the server-side middleware that then talks to the database.
• Type 4, the pure-java driver that uses database native protocol.

Note also a type called an internal JDBC driver - a driver embedded with JRE in Java-enabled SQL databases. It is used for Java stored procedures. This does not fit into the classification scheme above, although it would likely resemble either a type 2 or type 4 driver (depending on whether the database itself is implemented in Java or not). An example of this is the KPRB (Kernel Program Bundled) driver supplied with Oracle RDBMS. "jdbc:default:connection" offers a relatively standard way of making such a connection (at least the Oracle database and Apache Derby support it). However, in the case of an internal JDBC driver, the JDBC client actually runs as part of the database being accessed, and so can access data directly rather than through network protocols.