The PreparedStatement in JDBC is used to obtain the automatically generated primary key value of the database,

The PreparedStatement in JDBC is used to obtain the automatically generated primary key value of the database,

PreparedStatement Interface

public interface PreparedStatement

Extends Statement

Indicates the objects of pre-compiled SQL statements.

SQL statements are pre-compiled and stored inPreparedStatementObject. This object can then be used to efficiently execute the statement multiple times. (Jdk api 1.6)

This interface can pre-compile SQL statements to prevent SQL Injection problems. When you execute the same SQL statement multiple times, because of pre-compilation, you do not need to re-compile the statement during execution, therefore, it is more efficient than Statement.

(Statement is compiled and executed every time an SQL Statement is executed)

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// Insert statement. The second parameter returns an int type primary key value PreparedStatement pstmt = conn. prepareStatement ("insert into tb_user values (null ,?,?) ", Statement. RETURN_GENERATED_KEYS );

// After the statement is executed, a result set ResultSet with the primary key value is returned.

ResultSet rs = ps. getGeneratedKeys ();

There are similar methods in Statement, which can be used in execute (String SQL, int autoGeneratedKeys) and other methods.

For example:

Import java. SQL. connection; import java. SQL. preparedStatement; import java. SQL. resultSet; import java. SQL. statement;/*** obtain the automatically generated primary key value of the database * @ author dingshuangen **/public class getKey {public static void main (String [] args) {Connection conn = DbUtil. getConnection (); PreparedStatement ps = null; PreparedStatement ps_h = null; ResultSet rs = null; try {// insert statement, the second parameter returns an int type primary key value ps = conn. prepareStatement ("insert I Nto tb_user values (null ,?,?) ", Statement. RETURN_GENERATED_KEYS); ps. setString (1, ""); ps. setString (2, "gourd"); // execute the sentence ps.exe cute (); // obtain the returned primary key value. The returned type is ResultSet result set rs = ps. getGeneratedKeys (); rs. next (); // obtain the primary key value int key = rs. getInt (1); System. out. println ("++ primary key ++" + key + "++" ++ "); ps_h = conn. prepareStatement ("insert into tb_hober values (null ,?,?) "); // Insert multiple data records cyclically. String [] holobby = {" dinner "," sleeping "," doubebean "}; for (String h: holobby) {ps_h.setInt (1, key); ps_h.setString (2, hsf-+ps_h.exe cute ();} System. out. println ("executed successfully");} catch (Exception e) {e. printStackTrace ();} finally {// disable all resources DbUtil. close (rs); DbUtil. close (ps); DbUtil. close (ps_h); DbUtil. close (conn );}}}

The execution result is as follows:

++ Primary key ++ 7 ++ successfully executed

Corresponding database table data:

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