java JDBC连接mysql数据库

前言

java连接数据库的学习笔记，我不得不承认java代码的繁杂。

概念

1 创建数据库链接的参数

String driver;
String url;
String user;
String password;

2 加载数据库

class.formName(driver)

3 获取数据库链接

Connection conn =
DriverManager
.getConnection(url,user,password);

4 编写sql语句

创建执行sql语句的对象

PreparedStatement stmt =
conn.prepareStatement(sql);

5 执行sql语句

修改操作

int row = stmt.executeUpdate();

执行查询操作

ResultSet rst = stmt.executeQuery();

6 处理结果

修改操作，提示执行结果

查询操作，变量结果集获取数据

while(rs.next){
rs.getString("列名");
}

代码实现

代码实例:

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.SQLException;

public class Main {

/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
insert();
update();
}

//插入操作
public static void insert(){
String driver = "com.mysql.jdbc.Driver";
String url = "jdbc:mysql://localhost:3306/qiandao";
String user = "root";
String password = "root";
try {
Class.forName(driver);
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
Connection conn = null;
PreparedStatement stmt = null;
try {
conn = DriverManager.getConnection(url,user,password);
if(conn!=null)
{
System.out.println("连接成功!");
}
String sql = "insert into t_sign_info"
+ "(stu_id,sign_date,sign_in,sign_out,sign_status)"
+" values(?,curdate(),curdate(),null,0)";
stmt =
conn.prepareStatement(sql);
stmt.setObject(1, 2);
int row = stmt.executeUpdate();
if(row>0){
System.out.println("签到成功");
}
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally{
if(stmt != null){
try {
stmt.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
if(conn != null){
try {
conn.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
//修改操作

public static void update(){
String driver = "com.mysql.jdbc.Driver";
String url = "jdbc:mysql://localhost:3306/qiandao?UseUncode=true&charsacterEncoding=utf-8";//处理编码
String user = "root";
String password = "root";
try {
Class.forName(driver);//反射 可以访问类的私有属性
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
Connection conn = null;
PreparedStatement stmt = null;
try {
conn = DriverManager
.getConnection(url,user,password);
String sql = "update t_stu_info"
+ " set stu_name = ?,stu_pwd = ?"
+ " where stu_id = ?";
stmt = conn.prepareStatement(sql);
stmt.setObject(1, "王五");
stmt.setObject(2, "999999");
stmt.setObject(3, 1);
int row = stmt.executeUpdate();
System.out.println(row);
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally{
if(stmt != null){
try {
stmt.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
if(conn != null){
try {
conn.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
}

封装jdbc

(实现增删改)

//封装jdbc操作
public static int executeUpdate(String sql,Object...objs){
int row = 0;
String driver = "com.mysql.jdbc.Driver";
String url = "jdbc:mysql://localhost:3306/qiandao?UseUncode=true&charsacterEncoding=utf-8";
String user = "root";
String password = "root";
try {
Class.forName(driver);//反射 可以访问类的私有属性
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
Connection conn = null;
PreparedStatement stmt = null;
try {
conn = DriverManager
.getConnection(url,user,password);
stmt = conn.prepareStatement(sql);
if(objs != null){//说明sql语句中有?
for (int i = 0; i < objs.length; i++) {
stmt.setObject(i+1, objs[i]);
}
}
row = stmt.executeUpdate();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return row;
}

方法调用

String sql = "insert into t_stu_info"
+" (stu_no,stu_name,stu_pwd)"
+" value(?,?,?)";//构建sql语句
int n = executeUpdate(sql, "S1003","赵六","123456");//方法调用
if(n>0){
System.out.println("成功");
}else{
System.out.println("失败");
}

(实现查询操作)

public static void executeQuery(String sql,Object...objs){
String driver = "com.mysql.jdbc.Driver";
String url = "jdbc:mysql://localhost:3306/qiandao?UseUncode=true&charsacterEncoding=utf-8";
String user = "root";
String password = "root";
try {
Class.forName(driver);//反射 可以访问类的私有属性
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
Connection conn = null;
PreparedStatement stmt = null;
ResultSet rst = null;
try {
conn = DriverManager
.getConnection(url,user,password);
stmt = conn.prepareStatement(sql);
if(objs != null){
for (int i = 0; i < objs.length; i++) {
stmt.setObject(i+1, objs[i]);
}
rst = stmt.executeQuery();
//              获取查询语句中列的信息
ResultSetMetaData meta =
rst.getMetaData();
//              获取列的数量
int count = meta.getColumnCount();
//              System.out.println(count);
while(rst.next()){
for (int i = 0; i < count; i++) {
String str = rst.getString(i+1);
System.out.print(str+"\t");
}
System.out.println();
}
}
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}

方法调用:

String sql = "select * from t_stu_info";
executeQuery(sql);