这是DAO层，第一次尝试，如有bug希望能即使反馈，我们共同进步。具体的用法和实现原理我会在前面几篇博客中补充更新。配置文件及项目目录结构会在下一篇中贴出！
package com.javasm.supermarket.dao;
import java.util.List;
import java.util.Map;
public interface DAO {
// 增加
void addObject(Object o);
// 删除
// void deleteObject(Object o);
// 修改
void updateObject(Object o);
/**
* 查询，可实现多查询或单一查询
* @param params
* @param tableName
* @return
*/
List<?> queryObject();
void deleteObject();
}DAOImpl层源码
package com.javasm.supermarket.impl;
import java.io.IOException;
import java.io.InputStream;
import java.lang.reflect.Field;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.sql.Timestamp;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Date;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Properties;
import com.javasm.supermarket.dao.DAO;
import com.javasm.supermarket.db.DBConnection;
public class DAOImpl implements DAO {
private static Properties objectConfigPath = new Properties();
private static Properties objectConfig = new Properties();
private static String className;
private static Class<?> objectClass;
private static Field[] fields;
private static String tableName;
private static String queryBuilder;
private static String deleteBuilder;
/**
*
* 加载配置文件,从配置文件中获取bean和bean对应的表明
*
*/
static {
try {
DAOImpl.class.getClassLoader();
InputStream objectConfigPathInputStream = ClassLoader
.getSystemResourceAsStream("objectConfigPath.properties");
objectConfigPath.load(objectConfigPathInputStream);
InputStream objectConfigInputStream = ClassLoader
.getSystemResourceAsStream(objectConfigPath
.getProperty("objectConfigPath"));
objectConfig.load(objectConfigInputStream);
className = objectConfig.getProperty("className");
tableName = objectConfig.getProperty("tableName");
queryBuilder = objectConfig.getProperty("queryBuilder");
deleteBuilder = objectConfig.getProperty("deleteBuilder");
objectClass = Class.forName(className);
fields = objectClass.getDeclaredFields();
} catch (IOException | ClassNotFoundException e) {
e.printStackTrace();
System.err.println("配置文件加载失败！");
}
}
/**
* 插入数据
*/
@Override
public void addObject(Object object) {
StringBuilder sql = new StringBuilder("INSERT " + tableName
+ " VALUES(");
Connection connection = null;
PreparedStatement preparedStatement = null;
// 用于存放传入的对象的参数，默认将id值（主键）的key设为0，方便条件设置
Map<Integer, Object> fieldsValues = new HashMap<Integer, Object>();
try {
for (int i = 0; i < fields.length; i++) {
fields[i].setAccessible(true);
fieldsValues.put(i, fields[i].get(object));
sql.append("?");
if (i < (fields.length - 1))
sql.append(", ");
}
sql.append(")");
connection = DBConnection.getConnection();
preparedStatement = connection.prepareStatement(sql.toString());
Class<?> fieldClass = null;
for (int i = 1; i <= fieldsValues.size(); i++) {
/**
* 获取存入map中对象的参数的类类型，根据类类型选择preparedStatement的set方法
*/
if (fieldsValues.get(i - 1) != null) {
fieldClass = fieldsValues.get(i - 1).getClass();
// 如果类类型为String.class，则执行setString
if (fieldClass.equals(String.class)) {
preparedStatement.setString(i,
(String) fieldsValues.get(i - 1));
}
// 如果类类型为Float.class，则执行setString
if (fieldClass.equals(Float.class)) {
preparedStatement.setFloat(i,
(Float) fieldsValues.get(i - 1));
}
// 如果类类型为Integer.class，则执行setString
if (fieldClass.equals(Integer.class)) {
preparedStatement.setInt(i,
(Integer) fieldsValues.get(i - 1));
}
// 如果类类型为Timestamp.class，则执行setString
if (fieldClass.equals(Timestamp.class)) {
preparedStatement.setTimestamp(i, new Timestamp(
((Date) fieldsValues.get(i - 1)).getTime()));
}
} else {
preparedStatement.setObject(i, null);
}
}
// 执行sql语句，返回更新参数
int columnsCount = preparedStatement.executeUpdate();
System.out.println("有" + columnsCount + "条数据被更新！");
} catch (SQLException e) {
e.printStackTrace();
} catch (SecurityException e) {
e.printStackTrace();
} catch (NumberFormatException e) {
e.printStackTrace();
} catch (IllegalArgumentException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
} finally {
DBConnection.close(connection, preparedStatement, null);
}
}
/**
*
* 删除数据，条件列表为空时删除所有数据
*/
@Override
public void deleteObject() {
StringBuilder sql = new StringBuilder(
"DELETE FROM order_info WHERE 1=1 ");
List<Map<String, Object>> params = builder(deleteBuilder);
Connection connection = null;
PreparedStatement preparedStatement = null;
try {
connection = DBConnection.getConnection();
if (params != null && params.size() > 0) {
for (int i = 0; i < params.size(); i++) {
Map<String, Object> map = params.get(i);
sql.append(" AND " + map.get("name") + " "
+ map.get("rela") + " " + map.get("value") + " ");
}
}
connection = DBConnection.getConnection();
preparedStatement = connection.prepareStatement(sql.toString());
preparedStatement.executeLargeUpdate();
} catch (SQLException e) {
e.printStackTrace();
System.out.println("删除失败！");
} catch (IllegalArgumentException e) {
e.printStackTrace();
} finally {
DBConnection.close(connection, preparedStatement, null);
}
}
/**
*
* 修改数据
*
*/
@Override
public void updateObject(Object object) {
StringBuilder sql = new StringBuilder("UPDATE " + tableName + " SET ");
Connection connection = null;
PreparedStatement preparedStatement = null;
// 用于存放传入的对象的参数，默认将id值（主键）的key设为0，方便条件设置
Map<Integer, Object> fieldsValues = new HashMap<Integer, Object>();
try {
for (int i = 0; i < fields.length; i++) {
fields[i].setAccessible(true);
if (i == 0) {
fieldsValues.put(fields.length - 1, fields[i].get(object));
continue;
}
sql.append(fields[i].getName());
sql.append("=?");
fieldsValues.put(i - 1, fields[i].get(object));
if (i < (fields.length - 1))
sql.append(", ");
if (i == (fields.length - 1)) {
sql.append(" WHERE ");
sql.append(fields[0].getName());
sql.append("=?");
}
}
connection = DBConnection.getConnection();
preparedStatement = connection.prepareStatement(sql.toString());
Class<?> fieldClass = null;
for (int i = 1; i <= fieldsValues.size(); i++) {
/**
* 获取存入map中对象的参数的类类型，根据类类型选择preparedStatement的set方法
*/
fieldClass = fieldsValues.get(i - 1).getClass();
// 如果类类型为String.class，则执行setString
if (fieldClass.equals(String.class)) {
preparedStatement.setString(i,
(String) fieldsValues.get(i - 1));
}
// 如果类类型为Float.class，则执行setString
if (fieldClass.equals(Float.class)) {
preparedStatement.setFloat(i,
(Float) fieldsValues.get(i - 1));
}
// 如果类类型为Integer.class，则执行setString
if (fieldClass.equals(Integer.class)) {
preparedStatement.setInt(i,
(Integer) fieldsValues.get(i - 1));
}
// 如果类类型为Timestamp.class，则执行setString
if (fieldClass.equals(Timestamp.class)) {
preparedStatement.setTimestamp(i, new Timestamp(
((Date) fieldsValues.get(i - 1)).getTime()));
}
}
// 执行sql语句，返回更新参数
int columnsCount = preparedStatement.executeUpdate();
System.out.println("有" + columnsCount + "条数据被更新！");
} catch (SQLException e) {
e.printStackTrace();
} catch (SecurityException e) {
e.printStackTrace();
} catch (NumberFormatException e) {
e.printStackTrace();
} catch (IllegalArgumentException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
} finally {
DBConnection.close(connection, preparedStatement, null);
}
}
/**
*
* 数据查询，查询条件列表为空时查询所有数据
*
*/
@Override
public List<?> queryObject() {
List<Map<String, Object>> params = builder(queryBuilder);
List<Object> objectList = new ArrayList<Object>();
StringBuilder sql = new StringBuilder("SELECT * FROM " + tableName
+ " WHERE 1=1");
Connection connection = null;
PreparedStatement preparedStatement = null;
ResultSet resultSet = null;
try {
connection = DBConnection.getConnection();
if (params != null && params.size() > 0) {
for (int i = 0; i < params.size(); i++) {
Map<String, Object> map = params.get(i);
sql.append(" AND " + map.get("name") + " "
+ map.get("rela") + " " + map.get("value") + " ");
}
}
preparedStatement = connection.prepareStatement(sql.toString());
resultSet = preparedStatement.executeQuery();
ResultSetMetaData resultSetMetaData = resultSet.getMetaData();
// 获取数据列数
int columnsCount = resultSetMetaData.getColumnCount();
Field field = null;
Object object = null;
while (resultSet.next()) {
/**
* 获取实例化对象
*/
object = objectClass.newInstance();
String columnName = null;
String columnTypeName = null;
String columnValue = null;
for (int i = 1; i <= columnsCount; i++) {
columnName = resultSetMetaData.getColumnName(i);
columnTypeName = resultSetMetaData.getColumnTypeName(i);
columnValue = resultSet.getString(i);
field = object.getClass().getDeclaredField(columnName);
field.setAccessible(true);
switch (columnTypeName) {
case "INT":
field.set(object, Integer.parseInt(columnValue));
break;
case "TINYINT":
field.set(object, Integer.parseInt(columnValue));
break;
case "VARCHAR":
field.set(object, columnValue);
break;
case "FLOAT":
field.set(object, Float.parseFloat(columnValue));
break;
case "DATETIME":
SimpleDateFormat simpleDateFormat = new SimpleDateFormat(
"yyyy-MM-dd HH:mm:ss");
field.set(object, simpleDateFormat.parse(columnValue));
break;
}
}
objectList.add(object);
}
} catch (SQLException e) {
e.printStackTrace();
} catch (NoSuchFieldException e) {
e.printStackTrace();
} catch (SecurityException e) {
e.printStackTrace();
} catch (NumberFormatException e) {
e.printStackTrace();
} catch (IllegalArgumentException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (ParseException e) {
e.printStackTrace();
} catch (InstantiationException e) {
e.printStackTrace();
} finally {
DBConnection.close(connection, preparedStatement, resultSet);
}
return objectList;
}
/**
* 从配置文件中提取删除或查询条件,如果传入的builder为null，则返回空列表
*
* @param builder
* @return
*/
private List<Map<String, Object>> builder(String builder) {
List<Map<String, Object>> paramList = new ArrayList<Map<String, Object>>();
if (builder.equals("null")) {
paramList = null;
} else {
Map<String, Object> param = null;
String[] values = null;
System.out.println(builder.contains(";"));
if (builder.contains(";")) {
String[] mapValue = builder.split(";");
for (String string : mapValue) {
values = string.split(",");
param = new HashMap<String, Object>();
param.put("name", values[0]);
param.put("rela", values[1]);
param.put("value", values[2]);
paramList.add(param);
}
} else {
values = builder.split(",");
param = new HashMap<String, Object>();
param.put("name", values[0]);
param.put("rela", values[1]);
param.put("value", values[2]);
paramList.add(param);
}
}
return paramList;
}
}