JDBC操作数据库(代码示范)
这篇文章作为基础，放在常用代码里面。平时需要写JDBC的时候，可以翻出来当范例。
Official doc: http://docs.oracle.com/javase/tutorial/jdbc/basics/connecting.html
以下是4种常用的数据库的JDBC访问URL和Driver：
##MySql - default port is 3306 database.url=jdbc:mysql://<server>:<port>/<dbname> database.driver=com.mysql.jdbc.Driver ##db2 - default port is 50000 database.url=jdbc:db2://<server>:<port>/<dbname> database.driver=com.ibm.db2.jcc.DB2Driver ##oracle - default port is 1521 database.url=jdbc:oracle:thin:@<server>:<port>:orcl database.driver=oracle.jdbc.driver.OracleDriver ##sqlserver - default port is 1433 database.url=jdbc:sqlserver://<server>:<port>;databaseName=<dbname> database.driver=com.microsoft.sqlserver.jdbc.SQLServerDriver
下面使用的常用类为DriverManager, Connection, Statement, PreparedStatement, Savepoint, ResultSet.
如果一个语句重复使用，那就用PreparedStatement, 它和Statement不同的是，PreparedStatement可以使得数据库对语句预编译并缓存，以后每次使用则不再需要编译，提高了性能。这里编译包含语句解析，纠错，计算Access Plan等等。PreparedStatement也比Statement更加易读易维护。它还支持batch错作。
Savepoint可以对一个Transaction进行分割。当一个Transaction失败，不一定全部回滚，可以回滚到前面某一个Savepoint。
Connection的属性中包含了对Transaction的操作，也包含了对数据的读写策略。可以使用setXXXX方法对其进行设置。
此外一个重要操作，在本例中没有体现。这里提一下，connection.getMetaData()。 MetaData中含有数据库的版本信息以及其对某些特殊resultset的支持。 比如types，concurrency，holdability。
下面是一个范例。整个逻辑是这样子的：
建表 - commit
插入3行 - commit
打印全表 - commit
更新全表 - commit
打印全表 - commit
删除一行 - commit
打印全表 - commit
删除一行 - savepoint
删除一行 - rollback(savepoint)
打印全表 - commit
销毁表 - commit
public class JDBCTest {
private Connection connection = null;
private static JDBCTest provider = new JDBCTest();
public static void main(String[] args) throws Exception {
Connection conn = provider.generateConnection();
try {
provider.createTable(conn);
provider.insert(conn);
provider.query(conn);
provider.update(conn);
provider.query(conn);
provider.delete(conn, true, 3);
provider.query(conn);
provider.delete(conn, false, 1);
Savepoint sp = conn.setSavepoint();
provider.delete(conn, false, 2);
conn.rollback(sp);
conn.commit();
provider.query(conn);
conn.commit();
} finally {
provider.dropTable(conn);
conn.close();
}
}
private synchronized Connection generateConnection() throws Exception {
Class.forName("com.ibm.db2.jcc.DB2Driver");
String url = "jdbc:db2://localhost:50000/FORUM";
Properties props = new Properties();
props.setProperty("user", "db2admin");
props.setProperty("password", "Passw0rd");
if (this.connection == null) {
this.connection = DriverManager.getConnection(url, props);
}
this.connection
.setTransactionIsolation(Connection.TRANSACTION_READ_COMMITTED);
this.connection.setAutoCommit(false);
return this.connection;
}
private void createTable(Connection conn) throws SQLException {
try {
StringBuffer sb = new StringBuffer()
.append(" CREATE TABLE TEST ( ")
.append(" ID INTEGER NOT NULL, ")
.append(" NAME CHAR(36) NOT NULL ")
.append(" ) ");
Statement s = conn.createStatement();
s.execute(sb.toString());
conn.commit();
} catch (SQLException e) {
conn.rollback();
throw e;
}
}
private void insert(Connection conn) throws SQLException {
PreparedStatement ps = null;
try {
StringBuffer sb = new StringBuffer()
.append(" INSERT INTO TEST VALUES ( ?, ?) ");
ps = conn.prepareStatement(sb.toString());
ps.setInt(1, 1);
ps.setString(2, "Bill");
ps.addBatch();
ps.setInt(1, 2);
ps.setString(2, "Joey");
ps.addBatch();
ps.setInt(1, 3);
ps.setString(2, "Kent");
ps.addBatch();
ps.executeBatch();
conn.commit();
} catch (SQLException e) {
conn.rollback();
throw e;
} finally {
try {
ps.close();
} catch (Exception e) {
}
}
}
private void update(Connection conn) throws SQLException {
PreparedStatement ps = null;
try {
StringBuffer sb = new StringBuffer()
.append(" UPDATE TEST SET NAME=? WHERE ID=? ");
ps = conn.prepareStatement(sb.toString());
ps.setInt(2, 1);
ps.setString(1, "Bill Update");
ps.addBatch();
ps.setInt(2, 2);
ps.setString(1, "Joey update");
ps.addBatch();
ps.setInt(2, 3);
ps.setString(1, "Kent update");
ps.addBatch();
ps.executeBatch();
conn.commit();
} catch (SQLException e) {
conn.rollback();
throw e;
} finally {
try {
ps.close();
} catch (Exception e) {
}
}
}
private void delete(Connection conn, boolean commite, int row) throws SQLException {
PreparedStatement ps = null;
try {
StringBuffer sb = new StringBuffer()
.append("DELETE FROM TEST WHERE ID=?");
ps = conn.prepareStatement(sb.toString());
ps.setInt(1, row);
ps.execute();
if (commite) {
conn.commit();
}
} catch (SQLException e) {
conn.rollback();
throw e;
} finally {
try {
ps.close();
} catch (Exception e) {
}
}
}
private void query(Connection conn) {
PreparedStatement ps = null;
try {
StringBuffer sb = new StringBuffer()
.append(" SELECT ID, NAME FROM TEST ");
StringBuffer output = new StringBuffer().append("Result:");
ps = conn.prepareStatement(sb.toString());
ResultSet rs = ps.executeQuery();
while (rs.next()) {
output.append("[ID=").append(rs.getInt(1)).append(",");
output.append("NAME=").append(rs.getString(2)).append("]");
}
System.out.println(output);
} catch (SQLException e) {
e.printStackTrace();
} finally {
try {
conn.commit();
ps.close();
} catch (Exception e) {
}
}
}
private void dropTable(Connection conn) throws SQLException {
try {
StringBuffer sb = new StringBuffer()
.append(" DROP TABLE TEST ");
Statement s = conn.createStatement();
s.execute(sb.toString());
conn.commit();
} catch (SQLException e) {
conn.rollback();
throw e;
}
}
}