JdbcTest.java类
package com.bjsxt;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public class JdbcTest {
//向Dpeartment表中添加一条数据
public void insertDepartments(String department_name,int location_id) {
Connection conn= null;
Statement state= null;
try {
/**驱动注册
Class.forName("com.mysql.jdbc.Driver");
//创建链接
conn=DriverManager.getConnection("jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=utf-8", "root", "123456");
*/
conn=JdbcUtil.getConnection();
String sql="insert into departments values(default,'"+department_name+"'"+location_id+")" ;
state = conn.createStatement();
int flag =state.executeUpdate(sql);
System.out.println(flag);
} catch (Exception e) {
e.printStackTrace();
}finally {
//JdbcUtil.closeStatement(state);
//JdbcUtil.closeConnection(conn);
JdbcUtil.closeResource(state, conn,null);
}
}
//更新departments表中department_id为6的数据，将部门名称修改为教学部，location_id为6
public void updateDepartments(String department_name,int location_id,int department_id) {
Connection conn =null;
Statement state=null;
try {
conn=JdbcUtil.getConnection();
state=conn.createStatement();
String sql="update departments d set d.department_name = '"+department_name+"',d.location_id = "+location_id+" where d.department_id ="+department_id;
int flag= state.executeUpdate(sql);
System.out.println(flag);
} catch (Exception e) {
// TODO: handle exception
e.printStackTrace();
}finally {
JdbcUtil.closeResource(state, conn,null);
}
}
//查询departments表中部门ID为6的部门信息
public void selectDepartmentsById(int departmentId) {
Connection conn=null;
Statement state=null;
ResultSet rs=null;
try {
conn=JdbcUtil.getConnection();
state= conn.createStatement();
String sql="select * from departments d where d.department_id = "+departmentId;
//执行返回结果
rs= state.executeQuery(sql);
while(rs.next()) {
System.out.println(rs.getInt("department_id")+" "+rs.getInt("department_name")+" "+rs.getInt(3));
}
}catch(Exception e) {
e.printStackTrace();
}finally {
JdbcUtil.closeResource(state, conn,rs);
}
}
public static void main(String[] args) {
// TODO Auto-generated method stub
JdbcTest test=new JdbcTest();
//test.insertDepartments("研发部", 1);
//test.updateDepartments("xx部", 8,4 );
//test.updateDepartments("啰嗦不", 6, 4);
//test.insertDepartments("干啥不", 10);
test.selectDepartmentsById(6);
}
}JdbcUtil.java类
package com.bjsxt;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ResourceBundle;
import java.sql.Statement;
/**
* Jdbc工具类
* @author wyz
*
*/
public class JdbcUtil {
private static String driver ;
private static String jdbcurl;
private static String username;
private static String password;
static {
//读取Properties文件
ResourceBundle bundle = ResourceBundle.getBundle("jdbc");
driver=bundle.getString(driver);
jdbcurl=bundle.getString(jdbcurl);
username=bundle.getString(username);
password=bundle.getString(password);
try {
Class.forName(driver);
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
}
//获取Connection对象
public static Connection getConnection() {
Connection conn=null;
try {
conn= DriverManager.getConnection(jdbcurl,username,password);
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return conn;
}
//关闭statement
public static void closeStatement(Statement state) {
try {
if(state!=null) {
state.close();
}
} catch (SQLException e) {
e.printStackTrace();
}
}
//关闭Connection
public static void closeConnection(Connection conn) {
try {
if(conn!=null) {
conn.close();
}
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
//关闭资源
public static void closeResource(Statement state,Connection conn,ResultSet rs) {
closeStatement(state);
closeConnection(conn);
closeResultSet(rs);
}
//关闭ResultSet链接
public static void closeResultSet(ResultSet rs) {
try {
if(rs!= null) {
rs.close();
}
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}jdbc.properties
driver =com.mysql.jdbc.Driver
jdbcurl =jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=utf-8
username =root
password =123456
还是报错跟之前同学们一样的问题，我看不太懂导包啥的我报错就是这样的
这是下面一章了，这章我就一直报错，找了好久没解决问题，学习下面一章的时候还是报错。麻烦老师详细解释一下
老师为什么我无论什么命令写在第二行选择执行的话都会报下面这个错，只要把第二行命令放在第一行就是一个查询窗口只有一条语句时它就能运行，如果多一行选择他就运行不出来，每次敲的时候都要敲一行运行完清一次窗口
老师这个空指针问题怎么解决
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