一、工具类型的封装及普适性泛型工具
1.1 封装DML方法
public int commonsUpdate(String sql, Object... args) {
Connection connection = null;
PreparedStatement preparedStatement = null;
try {
connection = DBUtils.getConnection();
preparedStatement = connection.prepareStatement(sql);
for (int i = 0; i < args.length; i++) {
preparedStatement.setObject(i + 1, args[i]);
}
return preparedStatement.executeUpdate();
} catch (SQLException e) {
e.printStackTrace();
} finally {
DBUtils.closeAll(null, preparedStatement, null);
}
return 0;
}
1.2 封装DQL方法
/**
* 公共查询方法 (可查询单个对象，也可查询多个对象,可以查任何一张表)
*
* @param sql
* @param args
* @return
*/
// select * from t_account
// select * from t_student
//工具不知道查的是什么 调用者知道
//封装对象、对象赋值 调用者清楚
public List<T> commonsSelect(String sql, RowMapper<T> rowMapper, Object... args) {
List<T> elements = new ArrayList<T>();
Connection connection = null;
PreparedStatement preparedStatement = null;
ResultSet resultSet = null;
try {
connection = DBUtils.getConnection();
preparedStatement = connection.prepareStatement(sql);
if(args !=null){
for (int i = 0; i < args.length; i++) {
preparedStatement.setObject(i + 1, args[i]);
}
}
resultSet = preparedStatement.executeQuery();
while (resultSet.next()) {
//根据查询到的结果完成ORM，如何进行对象的创建及赋值？
T t = rowMapper.getRow(resultSet);//回调---->调用者提供的一个封装方法ORM
elements.add(t);
}
} catch (SQLException e) {
e.printStackTrace();
} finally {
DBUtils.closeAll(null, preparedStatement, resultSet);
}
return elements;
}
二、用户案例
entity:
package com.t1.entity;
public class User {
private int id;
private String username;
private String password;
private String sex;
private String email;
private String address;
@Override
public String toString() {
return "User{" +
"id=" + id +
", username='" + username + '\'' +
", password='" + password + '\'' +
", sex='" + sex + '\'' +
", email='" + email + '\'' +
", address='" + address + '\'' +
'}';
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
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;
}
public String getSex() {
return sex;
}
public void setSex(String sex) {
this.sex = sex;
}
public String getEmail() {
return email;
}
public void setEmail(String email) {
this.email = email;
}
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
public User() {
}
public User(int id, String username, String password, String sex, String email, String address) {
this.id = id;
this.username = username;
this.password = password;
this.sex = sex;
this.email = email;
this.address = address;
}
}
utils:
//DBUtils工具类
package com.t1.utils;
import java.io.IOException;
import java.io.InputStream;
import java.sql.*;
import java.util.Properties;
public class DBUtils {
private static final Properties PROPERTIES = new Properties();
//为当前线程绑定一个Connection连接。从头到尾
private static final ThreadLocal<Connection> THREAD_LOCAL = new ThreadLocal<Connection>();
static {
InputStream is = DBUtils.class.getResourceAsStream("/db.properties");
try {
PROPERTIES.load(is);
Class.forName(PROPERTIES.getProperty("driver"));
} catch (IOException e) {
e.printStackTrace();
} catch (
