数据库连接操作类，该类提供创建数据库连接getConnection和release释放资源
package com.demo.JDBC;
import java.sql.*;
public class BaseDate {
/**
* MySQL驱动全路径
*/
private static final String DRIDER = "com.mysql.cj.jdbc.Driver";
/**
* MySQL连接URL
*/
private static final String URL = "jdbc:mysql://localhost:3306/avue";
/**
* 数据库用户名
*/
private static final String USER = "root";
/**
* 数据库密码
*/
private static final String PASSWORD = "123456";
public static Connection getConnection() {
try {
//注册MySQL驱动
Class.forName(DRIDER);
//创建与数据库的连接
return DriverManager.getConnection(URL,USER,PASSWORD);
} catch (ClassNotFoundException e) {
e.printStackTrace();
throw new RuntimeException("找不到驱动包");
} catch (SQLException e) {
e.printStackTrace();
throw new RuntimeException("创建数据库连接失败");
}
}
/**
* 释放JDBC的资源
* @param conn
* @param ps
* @param rs
*/
public static void release(Connection conn, PreparedStatement ps, ResultSet rs){
if (rs != null) {
try {
rs.close();
rs = null;
} catch (SQLException e) {
e.printStackTrace();
throw new RuntimeException("结果集资源释放失败");
}
}
if (ps != null) {
try {
ps.close();
ps = null;
} catch (SQLException e) {
e.printStackTrace();
throw new RuntimeException("SQL会话资源释放失败");
}
}
if (conn != null) {
try {
conn.close();
conn=null;
} catch (SQLException e) {
e.printStackTrace();
throw new RuntimeException("数据库连接资源释放失败");
}
}
}
}
数据库的操作类
package com.demo.JDBC;
import java.lang.reflect.Field;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.*;
/**
* @author 伍英杰
* @param
*/
public class CrudDao {
/**
* 数据库连接对象
*/
private Connection conn;
/**
* 结果集对象
*/
private ResultSet rs;
/**
* SQl执行对象，使用Statement的子接口PreparedStatement有效防止SQL注入攻击
*/
private PreparedStatement ps;
/**
* 实体类的Class对象，需要将结果集封装成指定实体类的Class对象，执行查询SQL必加
*/
private Class cs;
public CrudDao(Class cs) {
this.cs = cs;
}
/**
* 执行更新SQL
* @param sql
* @param ob
*/
public int executeUpdate(String sql, Object...ob) {
//获取数据库连接对象
conn = BaseDate.getConnection();
int colums = 0;
try {
if (conn != null) {
//关闭自动提交事务，方便使用事务
conn.setAutoCommit(false);
ps = conn.prepareStatement(sql);
bind(ob);
colums = ps.executeUpdate();
//事务提交
conn.commit();
} else {
//事务回滚
conn.rollback();
throw new RuntimeException("没找到连接对象");
}
return colums;
} catch (Exception e) {
e.printStackTrace();
throw new RuntimeException("执行SQL出错");
}
}
/**
* 执行查询SQL
* @param sql
* @param ob
*/
public List executeQuery(String sql, Object...ob) {
//获取数据库连接对象
conn = BaseDate.getConnection();
List list = new ArrayList<>();
try {
if (conn != null) {
//使用数据库连接对象创建SQL执行对象
ps = conn.prepareStatement(sql);
//调用参数绑定方法
bind(ob);
//执行查询方法，并接受返回值
rs = ps.executeQuery();
while (rs.next()){
//调用结果集封装方法，将返回值添加到List集合当中
list.add(toBean());
}
return list;
} else {
throw new RuntimeException("没找到连接对象");
}
} catch (SQLException e) {
e.printStackTrace();
throw new RuntimeException("执行SQL出错");
} finally {
//释放数据库连接资源
BaseDate.release(conn,ps,rs);
}
}
/**
* 执行多条查询SQL
* LinkedHashMap的Key是SQL语句（注意不能重复），value是查询条件参数
* 参数为何使用LinkedHashMap集合而不是Map接口，为了保证数据的有序性
* @param map
* @return
*/
public List> executeQueryLists(LinkedHashMap map) {
//获取数据库连接对象
conn = BaseDate.getConnection();
List> lists = new ArrayList<>();
try {
if (conn != null) {
//遍历Map集合
Set> entries =
map.entrySet();
for (Map.Entry entry:entries) {
List list = new ArrayList<>();
//创建执行对象
ps = conn.prepareStatement(entry.getKey());
//绑定参数
bind(entry.getValue());
//执行查询方法
rs = ps.executeQuery();
//遍历结果集，并调用结果集封装方法
while (rs.next()) {
list.add(toBean());
}
//添加到集合
lists.add(list);
}
return lists;
} else {
throw new RuntimeException("没找到连接对象");
}
} catch (SQLException e) {
e.printStackTrace();
throw new RuntimeException("执行SQL出错");
} finally {
//释放资源
BaseDate.release(conn,ps,rs);
}
}
/**
* 执行多条更新SQL语句
* @param map
*/
public int executeUpdates(Map map) {
conn = BaseDate.getConnection();
//影响行数
int colums = 0;
if (conn != null) {
try {
//关闭自动提交事务，方便使用事务
conn.setAutoCommit(false);
Set> entries =
map.entrySet();
for (Map.Entry entry:entries) {
ps = conn.prepareStatement(entry.getKey());
bind(entry.getValue());
colums+=ps.executeUpdate();
}
//提交事务
conn.commit();
} catch (SQLException e) {
try {
//事务回滚
conn.rollback();
} catch (SQLException e1) {
e1.printStackTrace();
throw new RuntimeException("事务回滚失败");
}
e.printStackTrace();
throw new RuntimeException("执行多条SQL出错");
}
return colums;
} else {
throw new RuntimeException("没找到数据库连接对象");
}
}
/**
* ORM映射
* @return
*/
private T toBean() {
try {
//创建实例对象
T t = (T) cs.newInstance();
//获取该Class对象的声明的所有方法
Field[] fields = cs.getDeclaredFields();
for (Field field:fields) {
//开启私有访问权限
field.setAccessible(true);
//@TableField是一个自定义注解，是用来指定属性在数据库中相对应的字段名
TableField tableField = field.getAnnotation(TableField.class);
Object value = null;
if (tableField!=null) {
//使用属性的自定义注解的value值从结果集当中取值
value = rs.getObject(tableField.value());
} else {
//使用属性名从结果集当中取值
value = rs.getObject(field.getName());
}
//添加到实例当中去
field.set(t,value);
}
return t;
} catch (Exception e) {
e.printStackTrace();
throw new RuntimeException("结果集封装失败");
}
}
/**
* 绑定SQL参数
* @param ob
*/
private void bind(Object[] ob) {
if (ob!=null&&ob.length>0) {
try {
for (int i = 0,k = ob.length; i < k; i++) {
//绑定参数，下标从1开始
ps.setObject((i+1),ob[i]);
}
} catch (SQLException e) {
e.printStackTrace();
throw new RuntimeException("绑定SQL参数出错");
}
}
}
}
测试类
package com.demo;
import com.demo.JDBC.CrudDao;
import com.demo.JDBC.User;
import java.util.*;
/**
* @author 伍英杰
*/
public class Demo {
public static void main(String[] args) {
CrudDao dao = new CrudDao<>(User.class);
LinkedHashMap map = new LinkedHashMap<>();
map.put("select * from user",new Object[]{});
map.put("select * from user u where u.id = ?",new Object[]{3});
List> lists = dao.executeQueryLists(map);
for (List list:lists) {
for (User user: list) {
System.out.println(user);
}
System.out.println("---------------------------------------");
}
}
}
自定义注解
package com.demo.JDBC;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
public @interface TableField {
public String value();
}
测试所用实体类
package com.demo.JDBC;
import java.io.Serializable;
import java.sql.Timestamp;
/**
*
*
*
*
* @author psj
* @since 2019-03-05
*/
public class User implements Serializable {
/**
* ID
*/
private Long id;
/**
* 创建日期
*/
@TableField("create_time")
private Timestamp createTime;
/**
* 邮箱
*/
private String email;
/**
* 状态：1启用、0禁用
*/
private Boolean enabled;
/**
* 手机号码
*/
@TableField("mobile_phone")
private String mobilePhone;
/**
* 姓名
*/
private String name;
/**
* 密码
*/
private String password;
/**
* 用户名
*/
private String username;
/**
* 最后修改密码的日期
*/
@TableField("last_password_reset_time")
private Timestamp lastPasswordResetTime;
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public Timestamp getCreateTime() {
return createTime;
}
public void setCreateTime(Timestamp createTime) {
this.createTime = createTime;
}
public String getEmail() {
return email;
}
public void setEmail(String email) {
this.email = email;
}
public Boolean getEnabled() {
return enabled;
}
public void setEnabled(Boolean enabled) {
this.enabled = enabled;
}
public String getMobilePhone() {
return mobilePhone;
}
public void setMobilePhone(String mobilePhone) {
this.mobilePhone = mobilePhone;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public Timestamp getLastPasswordResetTime() {
return lastPasswordResetTime;
}
public void setLastPasswordResetTime(Timestamp lastPasswordResetTime) {
this.lastPasswordResetTime = lastPasswordResetTime;
}
@Override
public String toString() {
return "User{" +
"id=" + id +
", createTime=" + createTime +
", email='" + email + '\'' +
", enabled=" + enabled +
", mobilePhone='" + mobilePhone + '\'' +
", name='" + name + '\'' +
", password='" + password + '\'' +
", username='" + username + '\'' +
", lastPasswordResetTime=" + lastPasswordResetTime +
'}';
}
}