目次
Java の高度な機能 - JDBC (パート 1)
レベル 1: データベースへの JDBC 接続
package jdbc;
import java.sql.*;
public class jdbcConn {
public static void getConn() {
/********** Begin **********/
try {
//1.注册驱动
} catch (ClassNotFoundException e) {
e.printStackTrace();
}a
/********** End **********/
/********** Begin **********/
Connection conn = null;
Statement statement = null;
//2.建立连接并创建数据库和表
/********** End **********/
finally {
try {
if(statement!=null)
statement.close();
if(conn!=null)
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
レベル 2: テーブル内のデータに対する JDBC 操作
package jdbc;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;
public class jdbcInsert {
public static void insert(){
/********** Begin **********/
try {
//加载驱动
Class.forName("com.mysql.jdbc.Driver" );
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
/********** End **********/
Connection conn = null;
PreparedStatement statement = null;
/********** Begin **********/
//连接并插入数据
try{
conn = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/mysql_db","root","123123");
PreparedStatement s = conn.prepareStatement("insert into student values(?,?,?,?)");
s.setInt(1,1);s.setString(2,"张三");s.setString(3,"男");s.setInt(4,19);
s.executeUpdate();
s.setInt(1,2);s.setString(2,"李四");s.setString(3,"女");s.setInt(4,18);
s.executeUpdate();
s.setInt(1,3);s.setString(2,"王五");s.setString(3,"男");s.setInt(4,20);
s.executeUpdate();
s=conn.prepareStatement("select * from student");
ResultSet r = s.executeQuery();
while(r.next()){
System.out.println(r.getString(1)+" "+r.getString(2)+" "+r.getString(3)+" "+r.getString(4));
}
} catch (SQLException e) {
e.printStackTrace();
}
/********** End **********/
finally {
try {
if (statement != null)
statement.close();
if (conn != null)
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
レベル 3: JDBC トランザクション
package jdbc;
import java.sql.*;
public class jdbcTransaction {
public static void transaction(){
try {
Class.forName("com.mysql.jdbc.Driver" );
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
Connection conn = null;
PreparedStatement ps = null;
/********** Begin **********/
//连接数据库并开启事务
String url = "jdbc:mysql://localhost:3306/mysql_db";
try {
conn = DriverManager.getConnection (url,"root","123123" );
conn.setAutoCommit(false);//关闭自动提交开启事务
ps = conn.prepareStatement("insert into student(id,name,sex,age) values(4,'赵六','女',21)");
ps.executeUpdate();
conn.commit();//提交事务
ps = conn.prepareStatement("insert in student(id,name,sex,age) values(5,'钱七','男',18)");
ps.executeUpdate();
conn.commit();//提交事务
} catch (SQLException e) {
try {
//事务回滚
conn.rollback();
} catch (SQLException e1) {
e1.printStackTrace();
}
}
/********** End **********/
finally {
try {
if(ps!=null)
ps.close();
if (conn != null)
conn.close();
} catch (SQLException e1) {
e1.printStackTrace();
}
}
}
}
Java の高度な機能 - JDBC (パート 2)
レベル 1: JDBC カプセル化のタイプを指定します
package step1;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
import test.News;
public class JDBCUtils {
/**
* 连接数据库
*/
private static Connection getConnection() {
Connection conn=null;
/********** Begin **********/
String url="jdbc:mysql://localhost:3306/mysql_db";
try {
Class.forName("com.mysql.jdbc.Driver");
conn = DriverManager.getConnection(url, "root","123123");
}catch (ClassNotFoundException e) {
e.printStackTrace();
}catch (SQLException e) {
e.printStackTrace();
}
/********** End **********/
return conn;
}
/**
* 更新数据方法
* @param news
* @throws SQLException
*/
public void update(News news) throws SQLException {
Connection conn = getConnection();
PreparedStatement ps = null;
/********** Begin **********/
String sql = "update news set title=?,author_name=? where id=?";
try{
ps = conn.prepareStatement(sql);
ps.setString(1, news.getTitle());
ps.setString(2, news.getAuthor_name());
ps.setInt(3, news.getId());
ps.executeUpdate();
}catch(SQLException e){
e.printStackTrace();
throw new SQLException("更新数据失败");
}finally{
close(null, ps, conn);
}
/********** End **********/
}
/**
* 查询所有数据
* @return
* @throws SQLException
*/
public List<News> findAll() throws SQLException {
Connection conn = getConnection();
PreparedStatement ps = null;
ResultSet rs = null;
News news = null;
List<News> newsList = new ArrayList<News>();
/********** Begin **********/
String sql = "select * from news";
try{
ps = conn.prepareStatement(sql);
rs = ps.executeQuery();
while(rs.next()){
news = new News();
news.setId(rs.getInt(1));
news.setTitle(rs.getString(2));
news.setAuthor_name(rs.getString(3));
newsList.add(news);
}
}catch(SQLException e){
e.printStackTrace();
throw new SQLException("查询所有数据失败");
}finally{
close(rs, ps, conn);
}
/********** End **********/
return newsList;
}
/**
* 删除方法
* @param id
* @throws SQLException
*/
public void delete(int id) throws SQLException{
Connection conn = getConnection();
PreparedStatement ps = null;
/********** Begin **********/
String sql = "delete from news where id=?";
try{
ps = conn.prepareStatement(sql);
ps.setInt(1,id);
ps.executeUpdate();
}catch(SQLException e){
e.printStackTrace();
throw new SQLException(" 删除数据失败");
}
finally{
close(null, ps, conn);
}
/********** End **********/
}
/**
* 增加对象
* @param news
* @throws SQLException
*/
public void insert(News news) throws SQLException {
Connection conn = getConnection();
PreparedStatement ps = null;
String sql = "insert into news(id,title,author_name)values(?,?,?)";
try{
ps = conn.prepareStatement(sql);
ps.setInt(1, news.getId());
ps.setString(2, news.getTitle());
ps.setString(3, news.getAuthor_name());
ps.executeUpdate();
}catch(SQLException e){
e.printStackTrace();
throw new SQLException("添加数据失败");
}finally{
close(null, ps, conn);
}
}
/**
* 根据id查询对象
* @param id
* @return
* @throws SQLException
*/
public News findById(int id) throws SQLException {
Connection conn = getConnection();
PreparedStatement ps = null;
ResultSet rs = null;
News news = null;
String sql = "select * from news where id=?";
try{
ps = conn.prepareStatement(sql);
ps.setInt(1, id);
rs = ps.executeQuery();
if(rs.next()){
news = new News();
news.setId(id);
news.setTitle(rs.getString(2));
news.setAuthor_name(rs.getString(3));
}
}catch(SQLException e){
e.printStackTrace();
throw new SQLException("根据ID查询数据失败");
}
finally{
close(rs, ps, conn);
}
return news;
}
/**
* 关闭数据库连接
* @param rs
* @param ps
* @param conn
*/
public static void close(ResultSet rs,PreparedStatement ps,Connection conn){
try {
if(rs!=null)rs.close();
if(ps!=null)ps.close();
if(conn!=null)conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
レベル 2: 汎用 JDBC カプセル化
package step2;
import java.lang.reflect.Field;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
public class JDBCUtils {
private static Connection getConnection() {
try {
Class.forName("com.mysql.jdbc.Driver");
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
String url="jdbc:mysql://localhost:3306/mysql_db";
Connection conn=null;
try {
conn = DriverManager.getConnection(url, "root","123123");
} catch (SQLException e) {
e.printStackTrace();
}
return conn;
}
/**
* 类名对应表，属性对应字段
* @param obj 传入的对象
* @return
*/
public void insert(Object obj) {
Connection conn = getConnection(); //连接数据库
PreparedStatement ps = null;
/********** Begin **********/
//获取obj的Class
Class<?> c = obj.getClass();
//利用StringBuffer进行插入SQL语句的构造
StringBuffer sb1 = new StringBuffer("insert into "+ c.getSimpleName() +"("); //通过反射获取类名映射表名
StringBuffer sb2 = new StringBuffer(" values("); //注意前面要多加一个空格 否则sql将连在一起
Field[] field = c.getDeclaredFields(); //获取对象的属性数组
for(int i = 0; i < field.length; i++) { //遍历属性构造SQL语句
if(i != field.length-1) {
sb1.append(field[i].getName()).append(",");
sb2.append("?,");
}else {
sb1.append(field[i].getName()).append(")");
sb2.append("?);");
}
}
String sql = sb1.append(sb2).toString();
try {
ps = conn.prepareStatement(sql);
for(int i = 0; i < field.length; i++) {
field[i].setAccessible(true); //设置属性的可访问性，可以访问私有属性
try { //通过Field的get(Object)方法获取Object对象的属性值
ps.setObject(i+1, field[i].get(obj)); //对预编译的SQL语句中的？进行赋值
} catch (Exception e) {
e.printStackTrace();
}
}
ps.execute(); //执行SQL
}
/********** End **********/
catch (SQLException e) {
e.printStackTrace();
}finally {
close(null,ps,conn);
}
}
/**
* 通过对象的Class获取对应表中的所有记录
* @param c
* @return
*/
public <T> List<T> selectAll(Class<T> c) {
Connection conn = getConnection();
List<T> list = new ArrayList<T>();
PreparedStatement ps = null;
ResultSet rs = null;
/********** Begin **********/
String sql = "select * from "+ c.getSimpleName()+";"; //通过反射获取类名对应表名构造SQL语句
Field[] field = c.getDeclaredFields(); //通过反射获取所有属性
try {
ps = conn.prepareStatement(sql);
rs = ps.executeQuery();
while(rs.next()) {
T obj = c.newInstance(); //通过反射构造一个T类型的实例
for(int i = 0; i < field.length; i++) {
field[i].setAccessible(true); //设置可以访问私有属性
field[i].set(obj, rs.getObject(field[i].getName())); //通过属性名获取结果集中的值赋值到实例对象中
}
list.add(obj); //将实例对象添加到list集合
}
}
/********** End **********/
catch (Exception e) {
e.printStackTrace();
}finally {
close(rs,ps,conn);
}
return list;
}
/**
* 通过主键(默认第一个属性)删除对象
* @param obj
* @return
*/
public void delete(Object obj) {
Connection conn = getConnection();
PreparedStatement ps = null;
/********** Begin **********/
//获取obj的Class
Class<?> c = obj.getClass();
//构造删除的SQL语句
StringBuffer sb = new StringBuffer("delete from ");
sb.append(c.getSimpleName()).append(" where ");
//获取对象属性数组
Field[] field = c.getDeclaredFields();
//设置第一个属性的可访问性
field[0].setAccessible(true);
//获取第一个属性的属性名构造删除sql
sb.append(field[0].getName()).append("=?");
String sql = sb.toString();
try {
ps = conn.prepareStatement(sql);
ps.setObject(1, field[0].get(obj));
ps.execute();
}
/********** End **********/
catch (Exception e) {
e.printStackTrace();
}finally {
close(null,ps,conn);
}
}
/**
* 模拟jdbc的更新操作，默认第一个属性为主键
* @param obj
* @return
*/
public void update(Object obj) {
Class<?> c = obj.getClass();//获取obj的Class
StringBuffer sb = new StringBuffer("update "+ c.getSimpleName() +" set ");//利用StringBuffer进行修改SQL语句的构造
Field[] field = c.getDeclaredFields();//通过反射获取对象的属性数组
for(int i = 1; i < field.length; i++) {
if(i != field.length-1) { //判断是否为最后一个属性，若不是则后增加逗号
sb.append(field[i].getName()).append("=?,");
}else { //若为最后一个属性则添加 where
sb.append(field[i].getName()).append("=? where ");
}
}
//默认第一个属性为主键，切更改时通过第一个属性进行更改
sb.append(field[0].getName() + "=?");
String sql = sb.toString()+";";
Connection conn = getConnection();//获取连接对象
PreparedStatement ps = null;
try {
ps = conn.prepareStatement(sql);
for(int i = 1; i < field.length; i++) {
field[i].setAccessible(true);//设置可以访问私有属性
ps.setObject(i, field[i].get(obj));//对预编译的SQL语句中的 ? 进行赋值
}
field[0].setAccessible(true);
ps.setObject(field.length, field[0].get(obj));
ps.execute();//执行sql语句
} catch (Exception e) {
e.printStackTrace();
}finally {
close(null,ps,conn);//关闭连接数据
}
}
public static void close(ResultSet rs,PreparedStatement ps,Connection conn){
try {
if(rs!=null) rs.close();
if(ps!=null) ps.close();
if(conn!=null) conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
public <T> Object selectById(Class<T> c,int id) {
String sql = "select * from "+ c.getSimpleName()+" where id="+id;
Field[] field = c.getDeclaredFields();
Connection conn = getConnection();
PreparedStatement ps = null;
ResultSet rs = null;
Object obj=null;
try {
ps = conn.prepareStatement(sql);
rs = ps.executeQuery();
obj = c.newInstance();
while(rs.next()) {
for(int i = 0; i < field.length; i++) {
field[i].setAccessible(true);
field[i].set(obj, rs.getObject(field[i].getName()));
}
}
} catch (Exception e) {
e.printStackTrace();
}finally {
close(rs,ps,conn);
}
return obj;
}
}
JDBC の基本的なプログラミング演習
レベル 1: JDBC が従業員のパスワードを更新します
package step1;
import java.sql.*;
public class UpdatePass {
// 修改数据
public static void updateDB() {
/********* Begin *********/
// 第一步：加载驱动
try {
Class.forName("com.mysql.jdbc.Driver");
} catch (ClassNotFoundException e1) {
// TODO 自动生成的 catch 块
e1.printStackTrace();
}
// 第二步：建立连接, "root"和"123123"是针对MySQL设置了用户名(root)和密码(123123)的情况
// 127.0.0.1:3306是mysql服务器地址及端口 数据库编码格式设置为utf-8
Connection conn = null;
PreparedStatement ps = null;
try {
String url = "jdbc:mysql://127.0.0.1:3306/tsgc?useUnicode=true&characterEncoding=utf8";
String user = "root";
String password = "123123";
conn = DriverManager.getConnection(url, user, password);
// 第三步：建立statement对象
String sql = "update employee set password='hello' where sex='女'";
ps = conn.prepareStatement(sql);
// 第四步：修改数据
ps.execute();
// 第五步：关闭statement对象和连接对象
} catch (SQLException e) {
// TODO 自动生成的 catch 块
e.printStackTrace();
} finally {
try {
ps.close();
conn.close();
} catch (SQLException e) {
// TODO 自动生成的 catch 块
e.printStackTrace();
}
}
/********* End *********/
}
}
レベル 2: JDBC クエリ従業員情報
package step1;
import java.sql.*;
public class QueryPass {
// 查询数据代码不用上实验报告
public static void queryDB() {
/********* Begin *********/
Connection conn = null;
PreparedStatement ps = null;
try {
// 第一步：加载驱动
Class.forName("com.mysql.jdbc.Driver");
// 第二步：建立连接, "root"和"123123"是针对MySQL设置了用户名(root)和密码(123123)的情况
// 127.0.0.1:3306是mysql服务器地址及端口 数据库编码格式设置为utf-8
String url = "jdbc:mysql://127.0.0.1:3306/tsgc?useUnicode=true&characterEncoding=utf8";
String user = "root";
String password = "123123";
conn = DriverManager.getConnection(url, user, password);
// 第三步：建立statement对象
String sql = "select * from employee";
ps = conn.prepareStatement(sql);
ResultSet rs = ps.executeQuery();
// 第四步：查询数据
while (rs.next()) {
String no = rs.getString(1);
String name = rs.getString(2);
Object password1 = rs.getString(3);
Object sex = rs.getString(4);
double salary = rs.getDouble(5);
System.out.println("no:" + no + "\tname:" + name + "\tpassword:" + password1 + "\tsex:" + sex
+ "\tsalary:" + salary);
}
} catch (Exception e) {
e.printStackTrace();
} finally {
// 第五步：关闭statement对象和连接对象
try {
ps.close();
conn.close();
} catch (SQLException e) {
// TODO 自动生成的 catch 块
e.printStackTrace();
}
}
/********* End *********/
}
}