java操作數(shù)據(jù)庫(kù)， 如果不進(jìn)行整合， 添加，刪除，修改，查詢等操作將會(huì)有太多的重復(fù)代碼出現(xiàn)， 操作不易， 同時(shí)也影響美觀， 因此，將重復(fù)的代碼進(jìn)行整合，形成一個(gè)類， 然后調(diào)用就會(huì)簡(jiǎn)單很多
package yteng;
//先在lib下引入包mysql-connector-java-5.1.39-bin.jar
import java.sql.*;
public class Db {
// MySQL 8.0 以下版本 - JDBC 驅(qū)動(dòng)名及數(shù)據(jù)庫(kù) URL
static final String DRIVER = "com.mysql.jdbc.Driver";
static final String DB_URL = "jdbc:mysql://localhost:3306/stu_info";
// MySQL 8.0 以上版本 - JDBC 驅(qū)動(dòng)名及數(shù)據(jù)庫(kù) URL
//static final String JDBC_DRIVER = "com.mysql.cj.jdbc.Driver";
//static final String DB_URL = "jdbc:mysql://localhost:3306/stu_info?useSSL=false&allowPublicKeyRetrieval=true&serverTimezone=UTC";
static final String USER = "root";
static final String PASS = "root";
public static Connection conn = null;
public static PreparedStatement ps = null;
public static ResultSet rs = null;
static {
try {
//加載驅(qū)動(dòng)
Class.forName(DRIVER); //將mysql驅(qū)動(dòng)注冊(cè)到DriverManager中去
//Class.forName 方法的作用，就是初始化給定的類
} catch(ClassNotFoundException e) {
System.out.println(e.getMessage());
}
}
//得到數(shù)據(jù)庫(kù)連接對(duì)象
public static Connection conn() {
if(conn == null){
//獲取連接
try {
conn = DriverManager.getConnection(DB_URL,USER,PASS);
} catch (SQLException e) {
e.printStackTrace();
}
//返回一個(gè)數(shù)據(jù)庫(kù)連接對(duì)象, 通過個(gè)對(duì)象就可以對(duì)數(shù)據(jù)庫(kù)進(jìn)行增刪除改查操作了
}
return conn;
}
//基本的增,刪,改操作
public static int exec(String sql, Object...args) {
conn = conn();
int count = 0;
try {
//prepareStatement對(duì)象防止sql注入的方式是把用戶非法輸入的單引號(hào)用\反斜杠做了轉(zhuǎn)義，從而達(dá)到了防止sql注入的目的
ps = conn.prepareStatement(sql);
//設(shè)置占位符參數(shù)
if(args != null) {
for(int i = 0; i < args.length; i++) {
ps.setObject(i+1, args[i]);
}
}
count = ps.executeUpdate();
//設(shè)置占位符參數(shù)
}
catch(SQLException e) {
System.out.println(e.getMessage());
}
return count;
}
//返回新增加數(shù)據(jù)的id
public static int lastInsertId(String sql, Object...args) {
conn = conn();
int id = -1;
try {
//prepareStatement對(duì)象防止sql注入的方式是把用戶非法輸入的單引號(hào)用\反斜杠做了轉(zhuǎn)義，從而達(dá)到了防止sql注入的目的
ps = conn.prepareStatement(sql,Statement.RETURN_GENERATED_KEYS);
//設(shè)置占位符參數(shù)
if(args != null) {
for(int i = 0; i < args.length; i++) {
ps.setObject(i+1, args[i]);
}
}
ps.executeUpdate();
rs = ps.getGeneratedKeys();
if(rs.next())
{
id = rs.getInt(1);
}
//設(shè)置占位符參數(shù)
}
catch(SQLException e) {
System.out.println(e.getMessage());
}
return id;
}
//查詢操作
public static ResultSet fetch(String sql, Object...args) {
conn = conn();
try {
ps = conn.prepareStatement(sql);
//設(shè)置占位符參數(shù)
if(args != null) {
for(int i = 0; i < args.length; i++) {
ps.setObject(i+1, args[i]);
}
}
rs = ps.executeQuery(); //返回 查詢的數(shù)據(jù)結(jié)果
//設(shè)置占位符參數(shù)
}
catch(SQLException e) {
System.out.println(e.getMessage());
}
return rs;
}
public static void close() {
try {
if(rs != null) {rs.close(); rs = null;}
if(ps != null) {ps.close(); ps = null;}
if(conn != null) {conn.close(); conn = null;}
}
catch(SQLException e) {
System.out.println(e.getMessage());
}
}
}Db.java下載
