（3）JDBC——————回想大学写的JDBC，我酸了
大学期间自己写的jdbc和工作后写的jdbc看完后我酸了！接下来介绍一下这个模板的层次结构和代码的解析。
- 这是一套比较完整的JDBC模板，用的是德鲁伊连接池，项目结构为：
- 主要层次结构为：
- 代码如下
- 【BaseDAO.java】
package com.dao;
import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.BeanHandler;
import org.apache.commons.dbutils.handlers.BeanListHandler;
import org.apache.commons.dbutils.handlers.ScalarHandler;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.sql.Connection;
import java.sql.SQLException;
import java.util.List;
/**
* 定义一个用来被继承的对数据库进行基本操作的Dao
*
* @author Tommey周
* @create 2020-04-11 13:02
*/
public abstract class BaseDao<T> {
private QueryRunner queryRunner = new QueryRunner();
// 定义一个变量来接收泛型的类型
private Class<T> type;
// 获取T的Class对象，获取泛型的类型，泛型是在被子类继承时才确定
public BaseDao() {
// 获取子类的类型
Class clazz = this.getClass();
// 获取父类的类型，ParameterizedType表示的是带泛型的类型，getGenericSuperclass()用来获取当前类的父类的类型
ParameterizedType parameterizedType = (ParameterizedType) clazz.getGenericSuperclass();
// 获取具体的泛型类型 getActualTypeArguments获取具体的泛型的类型，这个方法会返回一个Type的数组
Type[] types = parameterizedType.getActualTypeArguments();
// 获取具体的泛型的类型
this.type = (Class<T>) types[0];
}
/**
* 通用的增删改操作
*/
public int update(Connection conn, String sql, Object... params) {
int count = 0;
try {
count = queryRunner.update(conn, sql, params);
} catch (SQLException e) {
e.printStackTrace();
}
return count;
}
/**
* 查询一个对象
*/
public T queryBean(Connection conn, String sql, Object... params) {
T t = null;
try {
t = queryRunner.query(conn, sql, new BeanHandler<T>(type), params);
} catch (SQLException e) {
e.printStackTrace();
}
return t;
}
/**
* 查询所有对象
*/
public List<T> queryBeanList(Connection conn, String sql, Object... params) {
List<T> list = null;
try {
list = queryRunner.query(conn, sql, new BeanListHandler<T>(type), params);
} catch (SQLException e) {
e.printStackTrace();
}
return list;
}
/**
* 查询单一值的方法，例如：count(1)这样的sql语句
*/
public Object queryValue(Connection conn, String sql, Object... params) {
Object count = null;
try {
count = queryRunner.query(conn, sql, new ScalarHandler<>(), params);
} catch (SQLException e) {
e.printStackTrace();
}
return count;
}
}
- 【UserDao.java】
package com.dao;
import com.bean.Page;
import com.bean.User;
import java.sql.Connection;
import java.util.List;
/**
* @author Tommey周
* @create 2020-04-11 13:01
*/
public interface UserDao {
/**
* 根据User对象中的用户名和密码从数据库中获取一条记录
*/
User queryUser(Connection conn, User user);
/**
* 根据User对象中的条件从数据库中获取多条记录
*/
List<User> queryList(Connection conn, User user);
/**
* 根据User对象中的条件分页从数据库中获取多条记录
*/
Page<User> queryPageList(Connection conn, Page<User> page, User user);
/**
* 根据User对象中的用户名从数据库中获取一条记录
*/
boolean checkUsername(Connection conn, User user);
/**
* 向数据库中插入User对象
*/
int saveUser(Connection conn, User user);
/**
* 向数据库中修改User对象
*/
int updateUser(Connection conn, User user);
/**
* 向数据库中删除User对象
*/
int deleteUser(Connection conn, User user);
}
- 【UserDaoImpl .java】
package com.dao.Impl;
import com.bean.Page;
import com.bean.User;
import com.dao.BaseDao;
import com.dao.UserDao;
import java.sql.Connection;
import java.util.List;
/**
* @author Tommey周
* @create 2020-04-11 13:01
*/
public class UserDaoImpl extends BaseDao<User> implements UserDao {
@Override
public User queryUser(Connection conn, User user) {
User bean = null;
String sql = "select id,password,name,address,phone from user where name = ? and password = ?";
//调用BaseDao中查询一个对象的方法
bean = queryBean(conn, sql, user.getName(), user.getPassword());
return bean;
}
@Override
public List<User> queryList(Connection conn, User user) {
List<User> users = null;
String sql = "select id,password,name,address,phone from user where name = ?";
users = queryBeanList(conn, sql, user.getName());
return users;
}
@Override
public Page<User> queryPageList(Connection conn, Page<User> page, User user) {
// 获取数据库中的总记录数
String sql = "select count(*) from user where name like concat('%',?,'%')";
// 调用BaseDao中获取一个单一值的方法
long totalRecord = (long) queryValue(conn, sql, user.getName());
// 将总记录数设置都page对象中
page.setTotalRecord((int) totalRecord);
// 获取当前页中的记录存放的List
String sql2 = "select id,password,name,address,phone from user where name like concat('%',?,'%') limit ?,?";
// 调用BaseDao中获取一个集合的方法
List<User> userList = queryBeanList(conn, sql2, user.getName(), page.getCurrent(), page.getSize());
// 将这个List设置到page对象中
page.setList(userList);
return page;
}
@Override
public boolean checkUsername(Connection conn, User user) {
User bean = null;
String sql = "select id,password,name,address,phone from user where name = ?";
//调用BaseDao中检验用户是否存在的方法
bean = queryBean(conn, sql, user.getName());
return bean != null;
}
@Override
public int saveUser(Connection conn, User user) {
String sql = "insert into user(password,name,address,phone) values(?,?,?,?)";
//调用BaseDao中通用的增删改的方法
return update(conn, sql, user.getPassword(), user.getName(), user.getAddress(), user.getPhone());
}
@Override
public int updateUser(Connection conn, User user) {
String sql = "update user set password = ?,name = ?,address = ?,phone = ? where id = ?";
//调用BaseDao中通用的增删改的方法
return update(conn, sql, user.getPassword(), user.getName(), user.getAddress(), user.getPhone(), user.getId());
}
@Override
public int deleteUser(Connection conn, User user) {
String sql = "delete from user where id = ?";
//调用BaseDao中通用的增删改的方法
return update(conn, sql, user.getId());
}
}
- 【User.java】
ackage com.bean;
import java.sql.Blob;
/**
* @author Tommey周
* @create 2020-04-09 22:15
*/
public class User {
private Integer id;
private String password;
private String name;
private String address;
private String phone;
private Blob photo;
public User() {
}
public User(Integer id, String password, String name, String address, String phone) {
this.id = id;
this.password = password;
this.name = name;
this.address = address;
this.phone = phone;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
public String getPhone() {
return phone;
}
public void setPhone(String phone) {
this.phone = phone;
}
public Blob getPhoto() {
return photo;
}
public void setPhoto(Blob photo) {
this.photo = photo;
}
@Override
public String toString() {
return "User{" +
"id=" + id +
", password='" + password + '\'' +
", name='" + name + '\'' +
", address='" + address + '\'' +
", phone='" + phone + '\'' +
", photo=" + photo +
'}';
}
}
- 【Page.java】
package com.bean;
import java.util.List;
/**
* @author Tommey周
* @create 2020-04-11 13:03
*/
public class Page<T> {
private static final int PAGE_CURRENT = 1; // 当前页码
public static final int PAGE_SIZE = 4; // 每页显示的记录数
private List<T> list; // 每页查到的记录存放的集合
private Integer current; // 当前页
private Integer size; //每页显示的条数
private int totalRecord; // 总记录数，通过查询数据库得到
public Page(Integer current, Integer size) {
this.current = (PAGE_CURRENT - 1) * PAGE_SIZE;
this.size = PAGE_SIZE;
if (current != null && size != null) {
this.current = (current - 1) * size;
this.size = size;
}
}
public List<T> getList() {
return list;
}
public void setList(List<T> list) {
this.list = list;
}
public int getCurrent() {
if(this.current != null){
return current;
}else {
return (PAGE_CURRENT - 1) * Page.PAGE_SIZE;
}
}
public void setCurrent(Integer current) {
this.current = current;
}
public Integer getSize() {
if (this.size != null){
return size;
}else {
return PAGE_SIZE;
}
}
public void setSize(Integer size) {
this.size = size;
}
public Integer getTotalRecord() {
return totalRecord;
}
public void setTotalRecord(Integer totalRecord) {
this.totalRecord = totalRecord;
}
@Override
public String toString() {
return "Page{" +
"list=" + list +
", 当前页为：" + current +
", 每页显示的条数为：" + size +
", 总记录数为：" + totalRecord +
'}';
}
}
- 【DruidUtils.java】
package com.util;
import com.alibaba.druid.pool.DruidDataSourceFactory;
import javax.sql.DataSource;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;
/**
* @author Tommey周
* @create 2020-04-14 23:28
*/
public class DruidUtils {
private static final String PROPERTIES_NAME = "druid.properties";
private static DataSource source;
static {
try {
Properties pro = new Properties();
pro.load(ClassLoader.getSystemClassLoader().getResourceAsStream(PROPERTIES_NAME));
source = DruidDataSourceFactory.createDataSource(pro);
} catch (Exception e) {
e.printStackTrace();
}
}
public static Connection getConnection() throws Exception {
return source.getConnection();
}
public static void close(Connection conn, Statement stmt, ResultSet rs) {
if (conn != null) {
try {
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if (stmt != null) {
try {
stmt.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if (rs != null) {
try {
rs.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
public static void main(String[] args) {
try {
System.out.println(DruidUtils.getConnection());
} catch (Exception e) {
e.printStackTrace();
}
}
}
- 【druid.properties】
url=jdbc:mysql://localhost:3306/test?rewriteBatchedStatements=true
username=root
password=root
driverClassName=com.mysql.jdbc.Driver
initialSize=10
maxActive=20
maxWait=1000
filters=wall
下一章，（1）H5+C3——————H5，选择器，盒子模型，布局，图标和文本样式