工具类封装
工具类封装
JDBCOperation DBUtil DBTool
1编码 向数据库MySQL中插入数据乱码
?useUnicode = true &characterEncoding = utf8
&useSSL=false
2：PrepareStatement 预处理statement
prepareStatement statemennt区别？
Sql 不同
Statement要求SQL语句直接追加数据内容
prepareStatement要求处理的数据单独的分离书写，增加程序可读性
SQL注入问题
Select *from user where username = “张三” and password = ‘’ or “1” = ”1”
prepareStatement 防止SQL的注入问题
3:SSL问题 安全链接 兼容性问题
Security socket layer 安全套接字协议层
4：工具类封装
什么情况下会考虑封装？
重复代码
经常用
如何封装？
DBUtil.java
静态方法
封装呢些功能？
1：建立连接（加载驱动，建立连接）
2：释放
注意工具类方法的参数和返回值类型
1：update( String sql ,Object[] objects) INSERT
UPDATE DELETE
2：query(String sql ,Object[] objects) SELECT
JDBCDemo.java
/**
*
*/
package com.zhiyou.jdbcDemo;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.SQLException;
/**
* @author Administrator
*
*/
public class JDBCDemo {
/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
insertData();
}
public static void insertData() {
try {
// 反射 机制
Class.forName("com.mysql.jdbc.Driver");
String url = "jdbc:mysql://localhost:3306/school?characterEncoding=utf8&useSSL=false";
String user = "root";
String password = "123456";
Connection coon = DriverManager.getConnection(url, user, password);
// ?相当于占位符
String sql = "insert into employer (e_name,e_age,e_date,d_id) values(?,?,?,?)";
PreparedStatement ps = coon.prepareStatement(sql);
// 设置占位符
ps.setString(1, "弗雷尔卓德");
ps.setInt(2, 134);
ps.setString(3, "2078-02-25");
ps.setInt(4, 2);
// 执行
int rs = ps.executeUpdate();
if (rs > 0) {
System.out.println("插入成功！");
}
ps.close();
coon.close();
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
DBUtil.java
/**
*
*/
package com.zhiyou.tools;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
/**
* @author Administrator
*
*/
public class DBUtil {
/**
* @param args
*/
// 驱动
private final static String DRIVER_CLASS = "com.mysql.jdbc.Driver";
// 账号密码URL
private final static String URL = "jdbc:mysql://localhost:3306/school?characterEncoding=utf8&useSSL=false";
private final static String USER = "root";
private final static String PASSWORD = "123456";
private static Connection connection = null;
private static PreparedStatement ps = null;
private static ResultSet rs = null;
// 获得驱动
static {
try {
Class.forName(DRIVER_CLASS);
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
// 获得一个链接
public static Connection getConnection() throws ClassNotFoundException, SQLException {
connection = DriverManager.getConnection(URL, USER, PASSWORD);
return connection;
}
// 释放的方法
public static void close() throws SQLException {
if (rs != null) {
rs.close();
}
if (ps != null) {
ps.close();
}
if (connection != null) {
connection.close();
}
}
// CRUD
public static int update(String sql, Object... obj) throws SQLException, ClassNotFoundException {
// 1：获取连接
connection = getConnection();
// 2：准备SQL语句
ps = connection.prepareStatement(sql);
// 填充？
for (int i = 0; i < obj.length; i++) {
ps.setObject(i + 1, obj[i]);
}
// 执行SQL并返回记录数
return ps.executeUpdate();
}
public static ResultSet query(String sql, Object... objects) throws SQLException, ClassNotFoundException {
// 获得连接
connection = getConnection();
// 准备SQL语句
ps = connection.prepareStatement(sql);
// 填充？
for (int i = 0; i < objects.length; i++) {
ps.setObject(i + 1, objects[i]);
}
rs = ps.executeQuery();
return rs;
}
}
EmployerObj.java
/**
*
*/
package com.zhiyou.model;
/**
* @author Administrator
*
*/
public class EmployerObj {
private int e_id;
private String e_name;
private int e_age;
public EmployerObj() {
super();
// TODO Auto-generated constructor stub
}
public EmployerObj(int e_id, String e_name, int e_age) {
super();
this.e_id = e_id;
this.e_name = e_name;
this.e_age = e_age;
}
public int getE_id() {
return e_id;
}
public void setE_id(int e_id) {
this.e_id = e_id;
}
public String getE_name() {
return e_name;
}
public void setE_name(String e_name) {
this.e_name = e_name;
}
public int getE_age() {
return e_age;
}
public void setE_age(int e_age) {
this.e_age = e_age;
}
@Override
public String toString() {
return "EmployerObj [e_id=" + e_id + ", e_name=" + e_name + ", e_age=" + e_age + "]";
}
}
IEmployerDao.java
/**
*
*/
package com.zhiyou.dao;
import java.util.List;
import com.zhiyou.model.EmployerObj;
/**
* @author Administrator
*
*/
public interface IEmployerDao {
// 获得所有员工信息
List getAll ();
}
EmployerDaoImpl.java
package com.zhiyou.impl;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
import com.zhiyou.model.EmployerObj;
import com.zhiyou.tools.DBUtil;
import com.zhiyou.dao.IEmployerDao;
public class EmployerDaoImpl implements IEmployerDao{
@Override
public List getAll() {
// TODO Auto-generated method stub
// 操作表
String sql = "select *from employer";
Object[] objects = {};
List list = new ArrayList<>();
try {
ResultSet rs = DBUtil.query(sql, objects);
while (rs.next()) {
int id = rs.getInt("e_id");
String name = rs.getString("e_name");
int age = rs.getInt("e_age");
EmployerObj obj = new EmployerObj(id, name, age);
list.add(obj);
}
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return list;
}
}
Test.java
/**
*
*/
package com.zhiyou.jdbcDemo;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.List;
import com.zhiyou.impl.EmployerDaoImpl;
import com.zhiyou.model.EmployerObj;
import com.zhiyou.tools.DBUtil;
/**
* @author Administrator
*
*/
public class Test {
/**
* @param args
* @throws SQLException
* @throws ClassNotFoundException
*/
public static void main(String[] args) throws ClassNotFoundException, SQLException {
// TODO Auto-generated method stub
DBUtil.getConnection();
String sql = "update employer set e_name=? where e_age = ?";
Object[] obj = { "维克托", 123 };
DBUtil.update(sql, obj);
String sql1 = "select * from employer where e_age list = employerDaoImpl.getAll();
System.out.println(list);
}
}