JDBC：
1. 概念：Java DataBase Connectivity Java 数据库连接， Java语言操作数据库
JDBC本质：其实是官方（sun公司）定义的一套操作所有关系型数据库的规则，即接口。
各个数据库厂商去实现这套接口，提供数据库驱动jar包。我们可以使用这套接口（JDBC）编程，真正执行的代码是驱动jar包中的实现类。
2. 快速入门：
步骤：
1. 导入驱动jar包 mysql-connector-java-5.1.37-bin.jar
1.复制mysql-connector-java-5.1.37-bin.jar到项目的libs目录下
2.右键-->Add As Library
2. 注册驱动
3. 获取数据库连接对象 Connection
4. 定义sql
5. 获取执行sql语句的对象 Statement
6. 执行sql，接受返回结果
7. 处理结果
8. 释放资源
实现连接数据库：
public class JDBCDemo1 {
public static void main(String[] args) throws SQLException, ClassNotFoundException {
//1. 导入驱动jar包
//2.注册驱动
Class.forName("com.mysql.jdbc.Driver");
//3.获取数据库连接对象
Connection conn= DriverManager.getConnection("jdbc:mysql://localhost:3306/test","root","root");
String sql="insert into user values(null,‘root‘,‘root‘)";
//4.定义sql语句
//5.获取执行sql的对象 Statement
Statement stmt = conn.createStatement();
//6.执行sql
int count = stmt.executeUpdate(sql);
//7.处理结果
System.out.println(count);
//8.释放资源
stmt.close();
conn.close();
}
}
使用 JDBC 开发使用到的包
JDBC 的核心 API
Connection：数据库连接对象
1. 功能：
1. 获取执行sql 的对象
* Statement createStatement()
* PreparedStatement prepareStatement(String sql)
2. 管理事务：
* 开启事务：setAutoCommit(boolean autoCommit) ：调用该方法设置参数为false，即开启事务
* 提交事务：commit()
* 回滚事务：rollback()
3. Statement：执行sql的对象
1. 执行sql
1. boolean execute(String sql) ：可以执行任意的sql 了解
2. int executeUpdate(String sql) ：执行DML（insert、update、delete）语句、DDL(create，alter、drop)语句
* 返回值：影响的行数，可以通过这个影响的行数判断DML语句是否执行成功 返回值>0的则执行成功，反之，则失败。
3. ResultSet executeQuery(String sql) ：执行DQL（select)语句
实现增删改查
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;
/* *
* account表 添加一条记录 insert 语句
*/
public class JDBCDemo2 {
public static void main(String[] args) {
Statement stmt = null ;
Connection conn = null ;
try {
// 1. 注册驱动
Class.forName( " com.mysql.jdbc.Driver " );
// 2. 定义sql
String sql = " insert into account values(null,‘王五‘,3000) " ;
// 3.获取Connection对象
conn = DriverManager.getConnection( " jdbc:mysql:///db3 " , " root " , " root " );
// 4.获取执行sql的对象 Statement
stmt = conn.createStatement();
// 5.执行sql
int count = stmt.executeUpdate(sql); // 影响的行数
// 6.处理结果
System. out .println(count);
if (count > 0 ){
System. out .println( " 添加成功！ " );
} else {
System. out .println( " 添加失败！ " );
}
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
} finally {
// stmt.close();
// 7. 释放资源
// 避免空指针异常
if (stmt != null ){
try {
stmt.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if (conn != null ){
try {
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
}
View Code
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;
/* *
* account表 修改记录
*/
public class JDBCDemo3 {
public static void main(String[] args) {
Connection conn = null ;
Statement stmt = null ;
try {
// 1. 注册驱动
Class.forName( " com.mysql.jdbc.Driver " );
// 2.获取连接对象
conn = DriverManager.getConnection( " jdbc:mysql:///db3 " , " root " , " root " );
// 3.定义sql
String sql = " update account set balance = 1500 where id = 3 " ;
// 4.获取执行sql对象
stmt = conn.createStatement();
// 5.执行sql
int count = stmt.executeUpdate(sql);
// 6.处理结果
System. out .println(count);
if (count > 0 ){
System. out .println( " 修改成功！ " );
} else {
System. out .println( " 修改失败 " );
}
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
} finally {
// 7.释放资源
if (stmt != null ){
try {
stmt.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if (conn != null ){
try {
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
}
View Code
import cn.itcast.util.JDBCUtils;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;
/* *
* account表 删除一条记录
*/
public class JDBCDemo4 {
public static void main(String[] args) {
Connection conn = null ;
Statement stmt = null ;
try {
// 1. 注册驱动
Class.forName( " com.mysql.jdbc.Driver " );
// 2.获取连接对象
conn = DriverManager.getConnection( " jdbc:mysql:///db3 " , " root " , " root " );
// conn = JDBCUtils.getConnection("jdbc:mysql: // /db3", "root", "root");
// 3.定义sql
String sql = " delete from account where id = 3 " ;
// 4.获取执行sql对象
stmt = conn.createStatement();
// 5.执行sql
int count = stmt.executeUpdate(sql);
// 6.处理结果
System. out .println(count);
if (count > 0 ){
System. out .println( " 删除成功！ " );
} else {
System. out .println( " 删除失败 " );
}
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
} finally {
// 7.释放资源
if (stmt != null ){
try {
stmt.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if (conn != null ){
try {
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
}
View Code
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;
/* *
* 执行DDL语句
*/
public class JDBCDemo5 {
public static void main(String[] args) {
Connection conn = null ;
Statement stmt = null ;
try {
// 1. 注册驱动
Class.forName( " com.mysql.jdbc.Driver " );
// 2.获取连接对象
conn = DriverManager.getConnection( " jdbc:mysql:///db3 " , " root " , " root " );
// 3.定义sql
String sql = " create table student (id int , name varchar(20)) " ;
// 4.获取执行sql对象
stmt = conn.createStatement();
// 5.执行sql
int count = stmt.executeUpdate(sql);
// 6.处理结果
System. out .println(count);
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
} finally {
// 7.释放资源
if (stmt != null ){
try {
stmt.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if (conn != null ){
try {
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
}
View Code
import java.sql.* ;
/* *
* 执行DDL语句
*/
public class JDBCDemo6 {
public static void main(String[] args) {
Connection conn = null ;
Statement stmt = null ;
ResultSet rs = null ;
try {
// 1. 注册驱动
Class.forName( " com.mysql.jdbc.Driver " );
// 2.获取连接对象
conn = DriverManager.getConnection( " jdbc:mysql:///db3 " , " root " , " root " );
// 3.定义sql
String sql = " select * from account " ;
// 4.获取执行sql对象
stmt = conn.createStatement();
// 5.执行sql
rs = stmt.executeQuery(sql);
// 6.处理结果
// 6.1 让游标向下移动一行
rs.next();
// 6.2 获取数据
int id = rs.getInt( 1 );
String name = rs.getString( " name " );
double balance = rs.getDouble( 3 );
System. out .println(id + " --- " + name + " --- " + balance);
// 6.1 让游标向下移动一行
rs.next();
// 6.2 获取数据
int id2 = rs.getInt( 1 );
String name2 = rs.getString( " name " );
double balance2 = rs.getDouble( 3 );
System. out .println(id2 + " --- " + name2 + " --- " + balance2);
// 6.1 让游标向下移动一行
rs.next();
// 6.2 获取数据
int id3 = rs.getInt( 1 );
String name3 = rs.getString( " name " );
double balance3 = rs.getDouble( 3 );
System. out .println(id3 + " --- " + name3 + " --- " + balance3);
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
} finally {
// 7.释放资源
if (rs != null ){
try {
rs.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if (stmt != null ){
try {
stmt.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if (conn != null ){
try {
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
}
View Code
ResultSet：结果集对象,封装查询结果
* boolean next(): 游标向下移动一行，判断当前行是否是最后一行末尾(是否有数据)，如果是，则返回false，
如果不是则返回true
* getXxx(参数):获取数据
* Xxx：代表数据类型 如： int getInt() , String getString()
* 参数：
1. int：代表列的编号,从1开始 如： getString(1)
2. String：代表列名称。 如： getDouble("balance")
* 注意：
* 使用步骤：
1. 游标向下移动一行
2. 判断是否有数据
3. 获取数据
//循环判断游标是否是最后一行末尾。
while(rs.next()){
//获取数据
//6.2 获取数据
int id = rs.getInt(1);
String name = rs.getString("name");
double balance = rs.getDouble(3);
System.out.println(id + "---" + name + "---" + balance);
}
PreparedStatement：执行sql的对象
PreparedStatement：执行sql的对象 1. SQL注入问题：在拼接sql时，有一些sql的特殊关键字参与字符串的拼接。会造成安全性问题 1. 输入用户随便，输入密码：a‘ or ‘a‘ = ‘a 2. sql：select * from user where username = ‘fhdsjkf‘ and password = ‘a‘ or ‘a‘ = ‘a‘ 2. 解决sql注入问题：使用PreparedStatement对象来解决 3. 预编译的SQL：参数使用?作为占位符 4. 步骤： 1. 导入驱动jar包 mysql-connector-java-5.1.37-bin.jar 2. 注册驱动 3. 获取数据库连接对象 Connection 4. 定义sql * 注意：sql的参数使用？作为占位符。 如：select * from user where username = ? and password = ?; 5. 获取执行sql语句的对象 PreparedStatement Connection.prepareStatement(String sql) 6. 给？赋值： * 方法： setXxx(参数1,参数2) * 参数1：？的位置编号 从1 开始 * 参数2：？的值 7. 执行sql，接受返回结果，不需要传递sql语句 8. 处理结果 9. 释放资源 5. 注意：后期都会使用PreparedStatement来完成增删改查的所有操作 1. 可以防止SQL注入 2. 效率更高
设置Bean类
public class UserDao {
private String username;
private String password;
public String getUsername() {
return username;
}
public void setUsername(String username) {
this .username = username;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this .password = password;
}
}
View Code
连接数据库
import com.web.domain.UserDao;
import java.sql. * ;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
public class JDBCDemo2 {
public static void main(String[] args) throws SQLException, ClassNotFoundException {
Class.forName( " com.mysql.jdbc.Driver " );
Connection conn = DriverManager.getConnection( " jdbc:mysql://localhost:3306/test " , " root " , " root " );
String sql = " select *from user " ;
PreparedStatement pstmt = conn.prepareStatement(sql);
conn.setAutoCommit( false );
ResultSet rs = pstmt.executeQuery();
conn.commit();
List list = new ArrayList<UserDao> ();
while (rs.next()){
String username =rs.getString( " username " );
String password =rs.getString( " password " );
UserDao userDao = new UserDao();
userDao.setUsername(username);
userDao.setPassword(password);
list.add(userDao);
}
conn.close();
pstmt.close();
Iterator <UserDao> it= list.iterator();
while (it.hasNext()){
UserDao userDao = it.next();
System. out .println(userDao.getUsername()+ " ================== " + userDao.getPassword());
}
}
}
View Code
优化
import com.web.domain.UserDao;
import java.sql. * ;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
public class JDBCDemo3 {
public static void main(String[] args) throws SQLException {
Connection conn = null ;
PreparedStatement pstmt = null ;
ResultSet rs = null ;
try {
Class.forName( " com.mysql.jdbc.Driver " );
conn = DriverManager.getConnection( " jdbc:mysql://localhost:3306/test " , " root " , " root " );
String sql = " select *from user " ;
pstmt = conn.prepareStatement(sql);
conn.setAutoCommit( false );
rs = pstmt.executeQuery();
conn.commit();
List list = new ArrayList<UserDao> ();
while (rs.next()){
String username =rs.getString( " username " );
String password =rs.getString( " password " );
UserDao userDao = new UserDao();
userDao.setUsername(username);
userDao.setPassword(password);
list.add(userDao);
}
Iterator <UserDao> it= list.iterator();
while (it.hasNext()){
UserDao userDao = it.next();
System. out .println(userDao.getUsername()+ " ================== " + userDao.getPassword());
}
} catch (Exception e){
e.printStackTrace();
} finally {
if (conn!= null ) conn.close();
if (pstmt!= null ) pstmt.close();
}
}
}
View Code
设置JDBC的连接工具类
import java.io.FileReader;
import java.io.IOException;
import java.net.URL;
import java.sql. * ;
import java.util.Properties;
// JDBC工具类
public class JDBCutils {
private static String url;
private static String user;
private static String password;
private static String driver;
// 文件的读取，只需要读取一次即可拿到这些值。使用静态代码块
static {
// 读取资源文件，获取值。
try {
// 1. 创建Properties集合类。
Properties pro = new Properties();
// 获取src路径下的文件的方式--->ClassLoader 类加载器
ClassLoader classLoader=JDBCutils. class .getClassLoader();
URL res =classLoader.getResource( " jdbc.properties " );
String path = res.getPath();
// 2. 加载文件
pro.load( new FileReader(path));
// 3. 获取数据，赋值
url = pro.getProperty( " url " );
user = pro.getProperty( " user " );
password = pro.getProperty( " password " );
driver = pro.getProperty( " driver " );
// 4. 注册驱动
Class.forName(driver);
} catch (IOException e) {
e.printStackTrace();
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
}
/* *
* 获取连接
* @return 连接对象
*/
public static Connection getConnection() throws SQLException {
return DriverManager.getConnection(url, user, password);
}
/* *
* 释放资源
* @param stmt
* @param conn
*/
public static void close(Statement stmt, Connection conn){
if ( stmt != null ){
try {
stmt.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if ( conn != null ){
try {
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
/* *
* 释放资源
* @param stmt
* @param conn
*/
public static void close(ResultSet rs, Statement stmt, Connection conn){
if ( rs != null ){
try {
rs.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if ( stmt != null ){
try {
stmt.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if ( conn != null ){
try {
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
View Code
jdbc文件
url=jdbc:mysql: // localhost:3306/test user= root password = root driver =com.mysql.jdbc.DriverView Code
连接
import com.web.domain.UserDao;
import com.web.utils.JDBCutils;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
public class JDBCDemo4 {
public static void main(String[] args) throws SQLException {
Connection conn = null ;
PreparedStatement pstmt = null ;
ResultSet rs = null ;
conn = JDBCutils.getConnection();
String sql =查看更多关于java:JDBC的使用方式的详细内容...
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