JDBC入门知识

JDBC全称叫Java Data Base Connectivity，是连接数据库的接口，不同数据库有不同的API接口，我要说的是oracle数据库提供的接口，怎么说呢，JDBC就是使用java语言来连接数据库，通过使用提供的各种接口和类库文件来实现连接，废话少说，我来试验一下连接的全过程。

1下载J2EE版本的eclipse，新建一个java项目来连接数据库，首先要把oracle的jdbc的jar包添加到项目中，下面是我的代码名字叫TestJDBC.java

import java.sql.*;

public class TestJDBC {

public static void main(String[] args) {
ResultSet rs = null;
Statement stmt = null;
Connection conn = null;
try {
Class.forName("oracle.jdbc.driver.OracleDriver");//新生成一个oracle数据库驱动的对象
conn = DriverManager.getConnection("jdbc:oracle:thin:@192.168.0.1:1521:SXT", "scott", "tiger");//驱动管家指派数据库
stmt = conn.createStatement();    //连接者生成一个语句
rs = stmt.executeQuery("select * from dept"); //执行sql语句结果付给rs
while(rs.next()) {              //将dept数据库的数据打印出来
System.out.println(rs.getString("deptno"));
System.out.println(rs.getInt("deptno"));
}
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
} finally {
try {
if(rs != null) {
rs.close();
rs = null;
}
if(stmt != null) {
stmt.close();
stmt = null;
}
if(conn != null) {
conn.close();
conn = null;
}
} catch (SQLException e) {
e.printStackTrace();
}
}
}

}

2一般情况下，所有连接数据库的方式都差不多，main方法开始生成的三个对象是固定的，只不过不同的数据库提供了不同的方法而已，JDBC提供了标准。下面是JDBC常用的一些语句和方法，我一一写下来供大家参考，

3向数据库中插入一条数据，TestDML.java

<pre name="code" class="java">import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class TestDML {

public static void main(String[] args) {
Statement stmt = null;
Connection conn = null;
try {
Class.forName("oracle.jdbc.driver.OracleDriver");
//new oracle.jdbc.driver.OracleDriver();
conn = DriverManager.getConnection("jdbc:oracle:thin:@192.168.0.1:1521:SXT", "scott", "tiger");
stmt = conn.createStatement();
String sql = "insert into dept2 values (98, 'GAME', 'BJ')";
stmt.executeUpdate(sql);
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
} finally {
try {
if(stmt != null) {
stmt.close();
stmt = null;
}
if(conn != null) {
conn.close();
conn = null;
}
} catch (SQLException e) {
e.printStackTrace();
}
}
}

}

4在命令行里插入一个带有三个参数的数据TestDML.java

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class TestDML2 {

public static void main(String[] args) {
if(args.length != 3) {
System.out.println("Parameter Error! Please Input Again!");
System.exit(-1);
}

int deptno = 0;

try {
deptno = Integer.parseInt(args[0]);
} catch (NumberFormatException e) {
System.out.println("Parameter Error! Deptno should be Number Format!");
System.exit(-1);
}

String dname = args[1];
String loc = args[2];

Statement stmt = null;
Connection conn = null;
try {
Class.forName("oracle.jdbc.driver.OracleDriver");
//new oracle.jdbc.driver.OracleDriver();
conn = DriverManager.getConnection("jdbc:oracle:thin:@192.168.0.1:1521:SXT", "scott", "tiger");
stmt = conn.createStatement();
String sql = "insert into dept2 values (" + deptno + ",'" + dname + "','" + loc + "')";
System.out.println(sql);
stmt.executeUpdate(sql);
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
} finally {
try {
if(stmt != null) {
stmt.close();
stmt = null;
}
if(conn != null) {
conn.close();
conn = null;
}
} catch (SQLException e) {
e.printStackTrace();
}
}
}

}

5一次执行多条语句TestBatch.java

import java.sql.*;
public class TestBatch {

public static void main(String[] args) throws Exception {
Class.forName("oracle.jdbc.driver.OracleDriver");
Connection conn = DriverManager.getConnection("jdbc:oracle:thin:@192.168.0.1:1521:SXT", "scott", "tiger");
/*
Statement stmt = conn.createStatement();
stmt.addBatch("insert into dept2 values (51, '500', 'haha')");
stmt.addBatch("insert into dept2 values (52, '500', 'haha')");
stmt.addBatch("insert into dept2 values (53, '500', 'haha')");
stmt.executeBatch();
stmt.close();
*/

PreparedStatement ps = conn.prepareStatement("insert into dept2 values (?, ?, ?)");
ps.setInt(1, 61);
ps.setString(2, "haha");
ps.setString(3, "bj");
ps.addBatch();

ps.setInt(1, 62);
ps.setString(2, "haha");
ps.setString(3, "bj");
ps.addBatch();

ps.setInt(1, 63);
ps.setString(2, "haha");
ps.setString(3, "bj");
ps.addBatch();

ps.executeBatch();
ps.close();

conn.close();

}

}

6简化sql语句输入的方法是使用preparedment方法

import java.sql.*;

public class TestPrepStmt {

public static void main(String[] args) {
if(args.length != 3) {
System.out.println("Parameter Error! Please Input Again!");
System.exit(-1);
}

int deptno = 0;

try {
deptno = Integer.parseInt(args[0]);
} catch (NumberFormatException e) {
System.out.println("Parameter Error! Deptno should be Number Format!");
System.exit(-1);
}

String dname = args[1];
String loc = args[2];

PreparedStatement pstmt = null;
Connection conn = null;
try {
Class.forName("oracle.jdbc.driver.OracleDriver");
//new oracle.jdbc.driver.OracleDriver();
conn = DriverManager.getConnection("jdbc:oracle:thin:@192.168.0.1:1521:SXT", "scott", "tiger");
pstmt = conn.prepareStatement("insert into dept2 values (?, ?, ?)");
pstmt.setInt(1, deptno);
pstmt.setString(2, dname);
pstmt.setString(3, loc);
pstmt.executeUpdate();
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
} finally {
try {
if(pstmt != null) {
pstmt.close();
pstmt = null;
}
if(conn != null) {
conn.close();
conn = null;
}
} catch (SQLException e) {
e.printStackTrace();
}
}
}

}

7有时候必须同步sql的操作，一般情况下是一条一条的sql语句执行，这样就出现好多问题，为了将sql命令先全部执行完成，使用Transaction方法

import java.sql.*;
public class TestTransaction {

public static void main(String[] args) {

Connection conn = null;
Statement stmt = null;

try {
Class.forName("oracle.jdbc.driver.OracleDriver");
conn = DriverManager.getConnection("jdbc:oracle:thin:@127.0.0.1:1521:SXT", "scott", "tiger");

conn.setAutoCommit(false);
stmt = conn.createStatement();
stmt.addBatch("insert into dept2 values (51, '500', 'haha')");
stmt.addBatch("insert into dept2 values (52, '500', 'haha')");
stmt.addBatch("insert into dept2 values (53, '500', 'haha')");
stmt.executeBatch();
conn.commit();
conn.setAutoCommit(true);
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch(SQLException e) {

e.printStackTrace();

try {
if(conn != null)
{
conn.rollback();
conn.setAutoCommit(true);
}
} catch (SQLException e1) {
e1.printStackTrace();
}
}finally {
try {
if(stmt != null)
stmt.close();
if(conn != null)
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
}

}

}

8为了方便的操作数据库的数据，要将statement的属性进行一些调整，使其游标可以随意定位数据。代码如下

import java.sql.*;

public class TestScroll {
public static void main(String args[]) {

try {
new oracle.jdbc.driver.OracleDriver();
String url = "jdbc:oracle:thin:@192.168.0.1:1521:SXT";
Connection conn = DriverManager
.getConnection(url, "scott", "tiger");
Statement stmt = conn.createStatement(
ResultSet.TYPE_SCROLL_INSENSITIVE,
ResultSet.CONCUR_READ_ONLY);
ResultSet rs = stmt
.executeQuery("select * from emp order by sal");
rs.next();
System.out.println(rs.getInt(1));
rs.last();
System.out.println(rs.getString(1));
System.out.println(rs.isLast());
System.out.println(rs.isAfterLast());
System.out.println(rs.getRow());
rs.previous();
System.out.println(rs.getString(1));
rs.absolute(6);
System.out.println(rs.getString(1));
rs.close();
stmt.close();
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}

9时间仓促写的比较急，下次有空再完善。