package JDBC;
import java.sql.*;import oracle.jdbc.*;
import java.util.*;
public class FirstJdbc {
public static void main(String[] args){
Driver d=new OracleDriver();
Properties p=new Properties();
p.setProperty("user", "orcl");
p.setProperty("password", "sys");
try {
Connection con=d.connect("jdbc:orcle:[email protected]:1521:ORCL", p);
Statement st=con.createStatement();
String sql="select * from student";
ResultSet rs=st.executeQuery(sql);
} catch (SQLException e) {
e.printStackTrace();
}
}
}
eclipse提示：
Exception in thread "main" java.lang.NullPointerException
at JDBC.FirstJdbc.main(FirstJdbc.java:14)
第14行是：Statement st=con.createStatement();
确认connect字符串没有错误的，可为啥还报空指针异常呢？谢谢解答！
import java.sql.*;import oracle.jdbc.*;
import java.util.*;
public class FirstJdbc {
public static void main(String[] args){
Driver d=new OracleDriver();
Properties p=new Properties();
p.setProperty("user", "orcl");
p.setProperty("password", "sys");
try {
Connection con=d.connect("jdbc:orcle:[email protected]:1521:ORCL", p);
Statement st=con.createStatement();
String sql="select * from student";
ResultSet rs=st.executeQuery(sql);
} catch (SQLException e) {
e.printStackTrace();
}
}
}
eclipse提示：
Exception in thread "main" java.lang.NullPointerException
at JDBC.FirstJdbc.main(FirstJdbc.java:14)
第14行是：Statement st=con.createStatement();
确认connect字符串没有错误的，可为啥还报空指针异常呢？谢谢解答！
import oracle.sql.*;
import oracle.jdbc.pool.OracleDataSource;public class JdbcOracle {
public static void main(String[] args) { /**URL格式：drivername:@driver_information
1,drivername主要有以下两种
jdbc:oracle:thin (thin驱动程序)
jdbc:oracle:oci (oci驱动程序)
2,driver_information
host_nameort:database_sid
*/ Connection conn = null;
Statement stmt = null;
ResultSet rs = null;
String url = "jdbc:oracle:thin:@localhost:1521:ORADB";
String username = "scott";
String password = "tiger";
try { /**一、注册驱动程序
方法一Class.forName("oracle.jdbc.OracleDriver";
*/ DriverManager.registerDriver(new oracle.jdbc.OracleDriver()); //二、打开数据库连接
/**方法一，使用oracle数据源对象?
oracle.jdbc.pool.OracleDataSource ds=new oracle.jdbc.pool.OracleDataSource();
ds.setServerName("localhost";
ds.setDatabaseName("ORADB"; //数据库存名
ds.setDriverType("oci"; //要使用的JDBC驱动程序（OracleDatasore的扩展）
ds.setURL("jdbc:oracle:thin:@localhost:1521:ORADB"; //指定数据库的URL（OracleDataSource的扩展）
ds.setDataSourceName(""; //底层数据源的名称
ds.setNetworkProtocol("tcp";//用于数据库通信的协议
ds.setPortNumber(1521);//端口号
ds.setUser("scott";
ds.setPassword("tiger";
Connection conn=ds.getConnection();
*/
//方法二、使用Drivermanger conn = DriverManager.getConnection(url, username, password); //设置事务提交模式
//conn.setAutoCommit(true);
//若禁止了自动提交模式,那么在关闭Connection对象时会执行一次自动隐式提交,以保证还没有提交的所有DML语句被自动提交 conn.setAutoCommit(false); //三、创建JDBC Statement对象 stmt = conn.createStatement(); //PreparedStatement pstmt=conn.prepareStatement("带有参数的SQL语句";
//CallableStatement cstmt=conn.prepareCall("调用存储过程的语句";
//四、从数据库获取行
/**select 语句用executeQuery()
insert,update,delete语句用executeUpdate()
若预先不知道要执行的SQL语句类型，那么用execute()
*/ rs = stmt.executeQuery("select id,name,age,sex,birth from employee";//五、从数据库获取行 while (rs.next()) {
int id = rs.getInt("id";
String name = rs.getString("name";
int age = rs.getInt("age";
String sex = rs.getString("sex";
Date birth = rs.getDate("birth";
}
//rs.close();
//六、向数据库中添加行(注：月份的编码是从0开始的，因此月份1代表2月) java.sql.Date date = new java.sql.Date(82, 10, 05);
int i = stmt.executeUpdate("insert into employee values" +
"(1,'qds',22,'1',TO_DATE(date,'YYYY,MM,DD'))";
//七、修改数据中的行 int j = stmt.executeUpdate("update employee set age=21 where id=1";
//八、从数据库中删除行 int k = stmt.executeUpdate("delete from employee set id=1";
//九、处理数据库的NULL值方法一:使用结果集对象的wasNull方法判断 conn.commit();
rs = stmt.executeQuery(
"select id,type_id,prod_name from product where id=1"; //此次假设type_id列为Null值
System.out.println("id=" + rs.getInt("id");
System.out.println("type_id=" + rs.getInt("type_id");
if (rs.wasNull()) {
System.out.println("type_id was null!";
}
System.out.println("prod_name=" + rs.getString("prod_name"); //九、处理数据库的NULL值方法二:使用JAVA包装器类.因为JAVA包装器类可以赋于NULL值
//java.lang.Integer typeId=(java.lang.Integer)rs.getObject("type_id";
//System.out.println(typeId);此时typeId的值为Null
//在向数据库插入或更新某一行为NULL值时,也可以使用JAVA包装器对象
//java.lang.Double price=null;
//int ii=stmt.executeUpdate("update products set price="+price+" where id=12"; rs.close(); //十,执行数据定义语言语句(DDL:CREATE,ALTER,DROP)----采用execute()方法执行DDL语句
//执行DDL语句会导致一次隐式提交,因此,如果你在发出DDL语句之前执行了一些未提交的DML语句,那么这些DML语句将被提交 boolean result = stmt.execute("create table customers(" +
"id integer constraint customers_pK primary key," +
"first_name varchar2(10) not null," +
"last_name varchar2(10) not null," +
"dob date," +
"phone varchar2(15)" +
""
;
if (result == true) {
System.out.println("The table has Created!";
}
else {
System.out.println("The table hasn't Create";
}
//-------------------------------------------------------------------------
}
catch (Exception e) {
System.out.println("error: " + e);
try {
conn.rollback();
}
catch (SQLException sqle) {}
}
finally { try {
if (rs != null)
rs.close();
}
catch (SQLException sqle) {
System.out.println("SQLState: " + sqle.getSQLState());
System.out.println("SQLErrorCode: 错误代码" + sqle.getErrorCode());
System.out.println("SQLErrorMessage:错误情况的字符串 " + sqle.toString());
} try {
if (stmt != null)
stmt.close();
}
catch (SQLException sqle1) {
System.out.println("SQLState: " + sqle1.getSQLState());
System.out.println("SQLErrorCode: 错误代码" + sqle1.getErrorCode());
System.out.println("SQLErrorMessage:错误情况的字符串 " + sqle1.toString());
} try {
if (conn != null)
conn.close();
}
catch (SQLException sqle2) {
System.out.println(sqle2.toString());
System.out.println(sqle2.getSQLState());
System.out.println(sqle2.getErrorCode());
} } }
}本文来自CSDN博客http://blog.csdn.net/cyz1980/archive/2006/01/11/575929.aspx