JDBC封装
1.前言
原生的JDBC的操作其实是比较繁琐的，而且其中有很多的重复性代码，这个时候，我们可以考虑自己对JDBC进行一个简单的封装，封装成自己想要的，比较方便的小工具。
2.封装JDBC
为了使得编辑参数更加方便，首先将数据库连接参数抽取出来放在配置文件jdcb.properties中
jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://127.0.0.1:3306/singerdb?useUnicode=true&characterEncoding=UTF-8
jdbc.user=root
jdbc.password=123456
然后在类加载的时候加载该配置文件，并且注册驱动类信息
private static Properties properties;
static {
properties = new Properties();
try {
properties.load(new FileInputStream("config/jdbc.properties"));
System.out.println("load config file finish");
Class.forName(properties.getProperty("jdbc.driver"));
} catch (FileNotFoundException e) {
System.out.println("jdbc config file not found " + e.getMessage());
} catch (IOException e) {
e.printStackTrace();
} catch (ClassNotFoundException e) {
System.out.println("jdbc class not found " + e.getMessage());
}
}
接着封装获取连接对象getConnection()
/**
* 01-获得数据库连接Connection
* @return Connection 数据库连接
*/
private static Connection getConnection() {
Connection connection = null;
try {
connection = DriverManager.getConnection(
properties.getProperty("jdbc.url"),
properties.getProperty("jdbc.user"),
properties.getProperty("jdbc.password"));
} catch (SQLException e) {
System.out.println("cannot get connection " + e.getMessage());
}
return connection;
}
然后封装关闭各种资源的方法close()
/**
* 关闭connection
* @param connection 连接池对象
*/
private static void close(Connection connection) {
if (connection != null) {
try {
connection.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
/**
* 关闭Statement
* @param statement
*/
private static void close(Statement statement) {
if (statement != null) {
try {
statement.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
/**
* 关闭ResultSet
*
* @param resultSet
*/
private static void close(ResultSet resultSet) {
if (resultSet != null) {
try {
resultSet.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
/**
* 关闭Connection 以及Statement
* @param connection
* @param statement
*/
private static void close(Connection connection, Statement statement) {
close(connection);
close(statement);
}
/**
* 关闭Connection，Statement以及ResultSet
* @param connection
* @param statement
* @param resultSet
*/
private static void close(Connection connection, Statement statement, ResultSet resultSet) {
close(connection, statement);
close(resultSet);
}
接着封装更新方法，正如所知道的，更新包括插入、删除、修改，所以可以将这些操作封装在一个方法即可
/**
* 03-更新操作
* @param sql 执行的SQL语句
* @param param 对应的参数列表
* @return
*/
public static boolean update(String sql, Object... param) {
PreparedStatement preparedStatement = null;
Connection connection = getConnection();
try {
preparedStatement = connection.prepareStatement(sql);
if (settingParams(preparedStatement, param) == false) {
return false;
}
int result = preparedStatement.executeUpdate();
if (result > 0) {
return true;
}
return false;
} catch (SQLException e) {
e.printStackTrace();
} finally {
close(connection, preparedStatement);
}
return false;
}
上面封装了一个方法settingParams()，作用是利用元数据信息，根据SQL语句中的占位符个数，将对应的参数注入进去
/**
* 02-设置参数
* @param preparedStatement Statement对象
* @param param 参数列表
* @return
* @throws SQLException
*/
private static boolean settingParams(PreparedStatement preparedStatement, Object... param) throws SQLException {
if (param != null && param.length > 0) {
ParameterMetaData parameterMetaData = preparedStatement.getParameterMetaData();
int paramCount = parameterMetaData.getParameterCount();
if (paramCount != param.length) {
return false;
}
for (int i = 0; i < paramCount; i++) {
preparedStatement.setObject(i + 1, param[i]);
}
}
return true;
}
由于查询返回的类型非常多，这里只是封装两个常用的方法，一个是queryForBean()返回单个对象，一个是queryForList()返回List，这里需要注意的是，由于只是简单的封装，所以没有做对象属性名与数据表列名的映射，所以需要保证属性名与列名相同，为了更加方便进行操作，使用了泛型机制，并且使用了反射技术进行属性的注入操作
/**
* 获取单个Bean
*
* @param sql 执行SQL语句
* @param param 对应的参数列表
* @param clazz 所要获取的对象的类型
* @param 对象的类型
* @return bean
*/
public static <T> T queryForBean(String sql, Class<T> clazz, Object... param) {
Connection connection = getConnection();
PreparedStatement preparedStatement = null;
ResultSet resultSet = null;
try {
preparedStatement = connection.prepareStatement(sql);
if (settingParams(preparedStatement, param) == false) {
return null;
}
resultSet = preparedStatement.executeQuery();
if (resultSet == null) {
return null;
}
if (resultSet.next()) {
T data = clazz.newInstance();
ResultSetMetaData resultSetMetaData = resultSet.getMetaData();
int columnCount = resultSetMetaData.getColumnCount();
for (int i = 0; i < columnCount; i++) {
String name = resultSetMetaData.getColumnName(i + 1);
Object rData = resultSet.getObject(name);
//System.out.println(name+"---"+rData);
JDBCUtils.bulidBean(data, name, rData);
}
//System.out.println(data);
return data;
} else {
return null;
}
} catch (Exception e) {
e.printStackTrace();
} finally {
close(connection, preparedStatement, resultSet);
}
return null;
}
/**
* 获取Bean并且封装成List
*
* @param sql 执行SQL语句
* @param param 对应的参数列表
* @param clazz 所要获取的对象的类型
* @param 对象的类型
* @return list
*/
public static <T> List<T> queryForList(String sql, Class<T> clazz,Object... param) {
Connection connection = getConnection();
PreparedStatement preparedStatement = null;
ResultSet resultSet = null;
try {
preparedStatement = connection.prepareStatement(sql);
if (settingParams(preparedStatement, param) == false) {
return null;
}
resultSet = preparedStatement.executeQuery();
if (resultSet == null) {
return null;
}
List<T> results = new ArrayList<>();
while (resultSet.next()) {
T data = clazz.newInstance();
ResultSetMetaData resultSetMetaData = resultSet.getMetaData();
int columnCount = resultSetMetaData.getColumnCount();
for (int i = 0; i < columnCount; i++) {
String name = resultSetMetaData.getColumnName(i + 1);
Object rData = resultSet.getObject(name);
JDBCUtils.bulidBean(data, name, rData);
}
results.add(data);
}
return results;
} catch (Exception e) {
e.printStackTrace();
} finally {
close(connection, preparedStatement, resultSet);
}
return null;
}
private static Object bulidBean(Object bean, String name, Object value){
try {
Class c = bean.getClass();
String firstChar = String.valueOf(name.charAt(0)).toUpperCase();
String meThodName="set"+firstChar+name.substring(1);
Field declaredField = c.getDeclaredField(name);
Class type = declaredField.getType();
Method declaredMethod = c.getDeclaredMethod(meThodName, type);
//System.out.println(meThodName+"---"+declaredField+"----"+type.getName()+"----"+value);
if(value instanceof Date){
value=String.valueOf(value);
}
declaredMethod.invoke(bean,value);
} catch (Exception e) {
e.printStackTrace();
} finally {
}
return bean;
}
至此，通过简单的封装，一个简单的JDBC操作工具就封装好了，这样，当需要的时候就可以非常方便地使用了，而且，当需要其他返回类型的时候，基本上只要按照上面的思路进行处理即可。
完整的代码如下所示：
package com.bruce.utils;
import java.io.*;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;
import java.util.Properties;
public class JDBCUtils {
private static Properties properties;
static {
properties = new Properties();
try {
properties.load(new FileInputStream("config/jdbc.properties"));
System.out.println("load config file finish");
Class.forName(properties.getProperty("jdbc.driver"));
} catch (FileNotFoundException e) {
System.out.println("jdbc config file not found " + e.getMessage());
} catch (IOException e) {
e.printStackTrace();
} catch (ClassNotFoundException e) {
System.out.println("jdbc class not found " + e.getMessage());
}
}
/**
* 01-获得数据库连接Connection
* @return Connection 数据库连接
*/
private static Connection getConnection() {
Connection connection = null;
try {
connection = DriverManager.getConnection(
properties.getProperty("jdbc.url"),
properties.getProperty("jdbc.user"),
properties.getProperty("jdbc.password"));
} catch (SQLException e) {
System.out.println("cannot get connection " + e.getMessage());
}
return connection;
}
/**
* 02-设置参数
* @param preparedStatement Statement对象
* @param param 参数列表
* @return
* @throws SQLException
*/
private static boolean settingParams(PreparedStatement preparedStatement, Object... param) throws SQLException {
if (param != null && param.length > 0) {
ParameterMetaData parameterMetaData = preparedStatement.getParameterMetaData();
int paramCount = parameterMetaData.getParameterCount();
if (paramCount != param.length) {
return false;
}
for (int i = 0; i < paramCount; i++) {
preparedStatement.setObject(i + 1, param[i]);
}
}
return true;
}
/**
* 03-更新操作
* @param sql 执行的SQL语句
* @param param 对应的参数列表
* @return
*/
public static boolean update(String sql, Object... param) {
PreparedStatement preparedStatement = null;
Connection connection = getConnection();
try {
preparedStatement = connection.prepareStatement(sql);
if (settingParams(preparedStatement, param) == false) {
return false;
}
int result = preparedStatement.executeUpdate();
if (result > 0) {
return true;
}
return false;
} catch (SQLException e) {
e.printStackTrace();
} finally {
close(connection, preparedStatement);
}
return false;
}
/**
* 获取单个Bean
*
* @param sql 执行SQL语句
* @param param 对应的参数列表
* @param clazz 所要获取的对象的类型
* @param 对象的类型
* @return bean
*/
public static <T> T queryForBean(String sql, Class<T> clazz, Object... param) {
Connection connection = getConnection();
PreparedStatement preparedStatement = null;
ResultSet resultSet = null;
try {
preparedStatement = connection.prepareStatement(sql);
if (settingParams(preparedStatement, param) == false) {
return null;
}
resultSet = preparedStatement.executeQuery();
if (resultSet == null) {
return null;
}
if (resultSet.next()) {
T data = clazz.newInstance();
ResultSetMetaData resultSetMetaData = resultSet.getMetaData();
int columnCount = resultSetMetaData.getColumnCount();
for (int i = 0; i < columnCount; i++) {
String name = resultSetMetaData.getColumnName(i + 1);
Object rData = resultSet.getObject(name);
//System.out.println(name+"---"+rData);
JDBCUtils.bulidBean(data, name, rData);
}
//System.out.println(data);
return data;
} else {
return null;
}
} catch (Exception e) {
e.printStackTrace();
} finally {
close(connection, preparedStatement, resultSet);
}
return null;
}
/**
* 获取Bean并且封装成List
*
* @param sql 执行SQL语句
* @param param 对应的参数列表
* @param clazz 所要获取的对象的类型
* @param 对象的类型
* @return list
*/
public static <T> List<T> queryForList(String sql, Class<T> clazz,Object... param) {
Connection connection = getConnection();
PreparedStatement preparedStatement = null;
ResultSet resultSet = null;
try {
preparedStatement = connection.prepareStatement(sql);
if (settingParams(preparedStatement, param) == false) {
return null;
}
resultSet = preparedStatement.executeQuery();
if (resultSet == null) {
return null;
}
List<T> results = new ArrayList<>();
while (resultSet.next()) {
T data = clazz.newInstance();
ResultSetMetaData resultSetMetaData = resultSet.getMetaData();
int columnCount = resultSetMetaData.getColumnCount();
for (int i = 0; i < columnCount; i++) {
String name = resultSetMetaData.getColumnName(i + 1);
Object rData = resultSet.getObject(name);
JDBCUtils.bulidBean(data, name, rData);
}
results.add(data);
}
return results;
} catch (Exception e) {
e.printStackTrace();
} finally {
close(connection, preparedStatement, resultSet);
}
return null;
}
/**
* 关闭connection
* @param connection 连接池对象
*/
private static void close(Connection connection) {
if (connection != null) {
try {
connection.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
/**
* 关闭Statement
* @param statement
*/
private static void close(Statement statement) {
if (statement != null) {
try {
statement.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
/**
* 关闭ResultSet
*
* @param resultSet
*/
private static void close(ResultSet resultSet) {
if (resultSet != null) {
try {
resultSet.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
/**
* 关闭Connection 以及Statement
* @param connection
* @param statement
*/
private static void close(Connection connection, Statement statement) {
close(connection);
close(statement);
}
/**
* 关闭Connection，Statement以及ResultSet
* @param connection
* @param statement
* @param resultSet
*/
private static void close(Connection connection, Statement statement, ResultSet resultSet) {
close(connection, statement);
close(resultSet);
}
private static Object bulidBean(Object bean, String name, Object value){
try {
Class c = bean.getClass();
String firstChar = String.valueOf(name.charAt(0)).toUpperCase();
String meThodName="set"+firstChar+name.substring(1);
Field declaredField = c.getDeclaredField(name);
Class type = declaredField.getType();
Method declaredMethod = c.getDeclaredMethod(meThodName, type);
//System.out.println(meThodName+"---"+declaredField+"----"+type.getName()+"----"+value);
if(value instanceof Date){
value=String.valueOf(value);
}
declaredMethod.invoke(bean,value);
} catch (Exception e) {
e.printStackTrace();
} finally {
}
return bean;
}
}