前言:
最近呢,接了一个PLC-ERP的项目,要使用RS232串口通信,时间很赶、实在没有办法了,就是用Java动身喽。好早学习Java的时候,仅仅封装了一个连接以及关闭数据库的类,这次呢,那肯定要抽象出操作的Event方法的。
有了BasicDao之后,在简单的增删改查中,你会体验到特别方便!
如何连接数据库就不说了(jdbc),重点在于封装操作MySQL数据库的方法,还是直接看代码!
package com.samego.java.dev.dao.basic;
import com.samego.java.dev.common.BasicConnection;
import com.samego.java.dev.dao.presenter.SameGoToolDao;
import org.apache.commons.beanutils.BeanUtils;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;
/**
* BaseDao的实现
* 所有的Dao都要继承该类
* Created by alic(AlicFeng) on 17-5-24.
* Email is alic@samego.com
*/
public class BasicDao {
private Connection connection;
private PreparedStatement preparedStatement;
private ResultSet resultSet;
/**
* 更新的通用方法 including update/insert/delete
*
* @param sql SQL
* @param paramsValue prepareStatement sql语句中占位符对应的值(如果没有占位符,传入null)
* @param logMessage 日志信息
* @return 数据库更新的数目
*/
public int update(String sql, Object[] paramsValue, String[] logMessage) {
int result = -1;
try {
connection = BasicConnection.getConnection();
preparedStatement = connection.prepareStatement(sql);
int count = preparedStatement.getParameterMetaData().getParameterCount();
if (paramsValue != null && paramsValue.length > 0) {
//循环给参数赋值
for (int i = 0; i < count; i++) {
preparedStatement.setObject(i + 1, paramsValue[i]);
}
}
result = preparedStatement.executeUpdate();
} catch (SQLException e) {
this.writeLog(logMessage);
e.printStackTrace();
} finally {
BasicConnection.closeConnection(null, preparedStatement, connection);
}
return result;
}
/**
* 查询通用方法
*
* @param sql SQL
* @param paramsValue prepareStatement
* @param tClass 对象的类
* @param logMessage 日志
* @param <T> 返回类的集合
* @return 返回类的集合
*/
public <T> List<T> query(String sql, Object[] paramsValue, Class<T> tClass, String[] logMessage) {
List<T> list = new ArrayList<>();
connection = BasicConnection.getConnection();
try {
preparedStatement = connection.prepareStatement(sql);
if (paramsValue != null && paramsValue.length > 0) {
for (int i = 0; i < paramsValue.length; i++) {
preparedStatement.setObject(i + 1, paramsValue[i]);
}
}
resultSet = preparedStatement.executeQuery();
ResultSetMetaData resultSetMetaData = resultSet.getMetaData();
int columnCount = resultSetMetaData.getColumnCount();
T t;
while (resultSet.next()) {
t = tClass.newInstance();
for (int i = 0; i < columnCount; i++) {
String columnName = resultSetMetaData.getColumnName(i + 1);
Object value = resultSet.getObject(columnName);
BeanUtils.copyProperty(t, columnName, value);
}
list.add(t);
}
} catch (Exception e) {
this.writeLog(logMessage);
e.printStackTrace();
} finally {
BasicConnection.closeConnection(resultSet, preparedStatement, connection);
}
return list;
}
/**
* @param sql SQL
* @param paramsValue prepareStatement
* @param columnName 查询的字段名
* @param logMessage 日志
* @return 数量值
*/
public Object queryByOne(String sql, Object[] paramsValue, String columnName, String[] logMessage) {
Object result = null;
connection = BasicConnection.getConnection();
try {
preparedStatement = connection.prepareStatement(sql);
if (paramsValue != null && paramsValue.length > 0) {
for (int i = 0; i < paramsValue.length; i++) {
preparedStatement.setObject(i + 1, paramsValue[i]);
}
}
resultSet = preparedStatement.executeQuery();
if (resultSet.next()) {
result = resultSet.getObject(columnName);
}
} catch (Exception e) {
this.writeLog(logMessage);
e.printStackTrace();
} finally {
BasicConnection.closeConnection(resultSet, preparedStatement, connection);
}
return result;
}
/**
* 写日志
*
* @param logMessage 日志信息
*/
private void writeLog(String[] logMessage) {
if (null != logMessage && 2 == logMessage.length) {
SameGoToolDao.queryLog(logMessage[0], logMessage[1], false);
}
}
}
封装好了之后,那么我们就早Dao类继承,使用简洁又简单!看代码
- update
@Override
public boolean updateFinishPerProductTimeUnit(int time) {
boolean result = false;
String[] logMessage = {"更改系统值", "修改每一件产品的用时失败"};
Object[] paramValues = {time};
if (super.update(SQLCommands.UPDATE_PER_PRODUCT_TIME_UNIT, paramValues, logMessage) > 0) {
result = true;
ETCVar.PRODUCT_UNIT_TIME = time;
SameGoToolDao.queryLog("更改系统值", "修改每一件产品的用时成功", true);
}
return result;
}
- query
@Override
public ArrayList<MachineWork> machineWorkSign() {
ArrayList<MachineWork> machineWorks = super.query(SQLCommands.MACHINE_WORK_SIGN_CHECK, null, MachineWork.class, null);
}
- queryByOne
@Override
public int getLastMonthFinishedOrderNum() {
Object[] paramsValues = {Strings.ORDER_STATUS_LIST[2]};
String[] logMessage = {"报告报表", "查询上个月的订单数失败"};
int lastMonthOrderFinishedNum = Integer.parseInt(super.queryByOne(SQLCommands.LAST_MONTH_FINISHED_ORDER_NUM, paramsValues, "order_num", logMessage).toString());
SameGoToolDao.queryLog("报告报表", "查询上个月的订单数成功", true);
return lastMonthOrderFinishedNum;
}
注意:
使用到的第三方Jar有
- org.apache.commons.beanutils.BeanUtils
- commons-logging-1.0.4.jar这个编辑代码看不出,但是一定要引入,上面的依赖这个
个人的建议:
1、对于SQL语句呢,最好集中在一个类文件
2、使用占位符赋值-PreparedStatement,防止SQL注入
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