五分钟搞定JDBC数据库连接

JDBC(Java Database Connectivity)

API allows Java programs to connect to databases, Imports for the JDBC classes and interfaces from package java.sql.

Database access is the same for all database vendors

The JVM uses a JDBC driver to translate generalized JDBC 
calls into vendor specific database calls 

Starting with Java SE 8, the JDBC-ODBC Bridge will no longer be included with the JDK.

Popular JDBC database URL formats

MySQL jdbc:mysql://hostname:portNumber/databaseName 
ORACLE jdbc:oracle:thin:@hostname:portNumber:databaseName

Typical JDBC Programming Procedure

1. Load the database driver
2. Obtain a connection 
4. Getting result sets (tables) from tables 
5. Navigate through the result sets 
6. Close the connection 

Step 1：load database driver class

Class.forName("com.mysql.jdbc.Driver");

Step 2：connect to database

Connection con = DriverManager.getConnection( "jdbc:mysql://host[:port]/books", uid, password);

Step 3：Create a SQL statement object
Statement sql = con.createStatement();

Step 4：Getting data from a table
ResultSet rs = sql.executeQuery("SELECT * FROM authors");

Step 5：Use methods of ResultSet
A ResultSet object maintains a cursor pointing to its current row of data. Initially the cursor is positioned before the first row.
next()

The next() method moves the cursor to the next row, 
and it returns false when there are no more rows in the ResultSet 
object, it can be used in a while loop to iterate through the result set. 

getString()、getBollean()、getLong()

 Values can be retrieved using either the index number of the column 
 or the name of the column (case insensitive)

eg:
String s = rs.getString(“firstName”); = String s = rs.getString(2);

获得列名：

ResultSetMetaData metaData = resultSet.getMetaData();
int numberOfColumns = metaData.getColumnCount();
//index从1开始遍历
for(int i=1;i<numberOfColumns;i++){
    metaData.getColumnName(i);
}

Step 6：close the Statement and Connection

try{
...
} catch (SQLException se) {
        // 处理 JDBC 查询错误
        se.printStackTrace();
} catch (ClassNotFoundException e) {
        // 处理 Class.forName 错误，找不到driver class
        e.printStackTrace();
} finally {
            // 关闭资源
            try {
                resultSet.close();              
                statement.close();
                connection.close();
            }catch(Exception e){
                e.printStackTrace();
            }
        }