jdbc增删查改
前言:
Java数据库连接(Java Database Connectivity,J 简称JDBC),简单来说就是 使用Java执行sql语句的,面向关系型数据库的java_API
- 创建 Directory包 > 取名为 lib
- 创建实体类(BankModel.java)
package com.kjzz;
public class Teacher{
// 成员变量
private int SID; // id
private String SName; // name
private String birthday; // birthday 生日
// 无参构造 / 有参构造
public Teacher(){
}
public Teacher(int SID, String SName,String birthday) {
this.SID = SID;
this.SName = SName;
this.birthday = birthday;
}
// get / set 方法
public int getSID() {
return SID;
}
public void setSID(int SID) {
this.SID = SID;
}
public String getSName() {
return SName;
}
public void setSName(String SName) {
this.SName = SName;
}
public String getBirthday(){
return birthday;
}
public void setBirthday(String birthday){
this.birthday = birthday;
}
}
5.创建数据库驱动类(DBUtill.java)
public class DBConn{
// 驱动 , 路径 , 用户名 密码
// DRIVER--URL---USER-PWD
public static String DRIVER = "com.mysql.jdbc.Driver";
// jdbc:数据库名:// localhost:端口号/连接的数据库
public static String URL = "jdbc:mysql://localhost:3306/test";
public static String USER = "root";
public static String PWD = "root";
// 获取链接,为了处理找不到这个类,所以要异常处理
static{
try{
Class.forName(DRIVER); // 通过这个驱动名去找这个类
} catch(ClassNotFoundException e){
e.printStackTrace();
}
}
// 连接
public static Connection getConnection(){ // 要导入sql的包 不要带jdbc的
Connection conn = null;
try{
// 获取链接用的
conn = DriverManager.getConnection(URL,USER,PWD)
// 路劲 用户名 密码
} catch(SQLException e){
e.printStackTrace();
}
}
/** 关闭连接
当数据库使用后必须关闭,如果没有关闭数据库,
数据库接口有限,下次不能连接
*/
public static void CloseConn(Conncetion conn,PerpredStatement prep,ResultSet rs){
try{
if(rs != null){ // 不等于空 说明在使用
rs.close();
}
if(perp != null){
prep.close();
}
if(coon != null){
coon.close();
}
}catch(Exception e){
e.printStackTrace();
}
}
// 测试
public static void main(String[] args) {
Connection conn = getConnectionV();
System.out.println("ConnDB测试" + conn);
}
// 输出结果 ConnDB测试 com.mysql.jdbc.JDBC4Connection@289d1c02
}
6.创建数据库操作类
public class ZSGC {
public static Connection conn = null; // 连接对象
public static PreparedStatement prep = null; // 处理语句
public static ResultSet rs = null; // 查询后返回的结果集
/* 查询方法 实现思路
1. 加载数据库驱动(已经写好了 连接)
2. 获取数据库连接
3. 通过Conncetion 实列获取 Statement 对象
4. 通过 Statement 实列执行 SQL 语句
5. 处理 ResultSet 结果集
6. 回收数据库资源
*/
public List ChaXun(){
List list = new ArrayList<>();
String SelectSql = "select * from teacher"; // 表
try {
conn = Conn.getConnection(); // 1. 连接
prep = conn.prepareStatement(SelectSql); // 2. 处理sql
rs = prep.executeQuery(); // 3. 查询返回的结果集
while(rs.next()){ //rs 有内容,不为空
Teacher t = new Teacher();
int ID = rs.getInt("sid");
String NAME = rs.getString("sname");
String BIRTHDAY = rs.getString("birthday");
t = new Teacher(ID,NAME,BIRTHDAY);
list.add(t); list.add(stu); // 都要加进list集合
}
} catch (SQLException e) {
e.printStackTrace();
} finally{
Conn.CloseConn(conn,prep,rs);
}
return list;
}
// 添加
public static boolean Insert(Teacher teacher){
int num = 0;
String InsertSql = "INSERT INTO teacher values(?,?,?)";
try {
conn = Conn.getConnection();
prep = conn.prepareStatement(InsertSql);
prep.setInt(1,teacher.getSID());
prep.setString(2,teacher.getSName());
prep.setString(3,teacher.getBirthday());
num = prep.executeUpdate();
} catch (SQLException e) {
e.printStackTrace();
} finally {
Conn.CloseConn(conn,prep,rs);
}
return num > 0;
}
// 删除
public static boolean Delete(int key){
int num = 0;
String DeleteSql = "Delete from teacher where id = ?";
try {
conn = Conn.getConnection();
// 执行sql语句
prep = conn.prepareStatement(DeleteSql);
prep.setInt(1,key);
num = prep.executeUpdate();
} catch (SQLException e) {
e.printStackTrace();
}finally{
Conn.CloseConn(conn,prep,rs);
}
return num > 0;
}
// 修改
public static boolean Update(Teacher teacher){
int num = 0; // 定义影响的行数
String UpdateSql = "update teacher set sid = ?,sname = ? where sid = ? ";
try {
conn = Conn.getConnection();
prep = conn.prepareStatement(UpdateSql);
prep.setInt(1,teacher.getSID());
prep.setString(2,teacher.getSName());
prep.setInt(3,teacher.getSID());
num = prep.executeUpdate(); // 增删改都是这个,然会INT类型
} catch (SQLException e) {
e.printStackTrace();
}finally {
Conn.CloseConn(conn, prep, rs);
}
return num > 0;
}
}
- 测试
public class Text1 {
public static void main(String[] args) {
Conn conn = new Conn();
System.out.println("conn = " + conn);
CRUD crud = new CRUD();
List list = crud.ChaXun();
for (Teacher t : list) {
System.out.println(t.getSID());
System.out.println(t.getSName());
System.out.println(t.getBirthday());
}
// 添加
Teacher t1 = new Teacher(3,"白居易","1001-11-11");
boolean insert = CRUD.Insert(t1);
if (insert == true){
System.out.println("添加成功");
} else{
System.out.println("添加失败");
}
// 修改
boolean delete = CRUD.Delete(2);
if (delete == true){
System.out.println("删除成功");
} else {
System.out.println("报错咯");
}
// 修改
Teacher t2 = new Teacher();
t2.setSID(1);
t2.setSName("张三");
t2.setSID(1);
boolean update = CRUD.Update(t2);
if (update == true){
System.out.println("1号名字已被修改为张三");
} else {
System.out.println("失败");
}
}
}