Java中JDBC工具类
项目结构
项目文件代码
log4j.properties：
用于在指定位置创建log.log文件，存储项目的异常。
# DEBUG\u8BBE\u7F6E\u8F93\u51FA\u65E5\u5FD7\u7EA7\u522B\uFF0C\u7531\u4E8E\u4E3ADEBUG\uFF0C\u6240\u4EE5ERROR\u3001WARN\u548CINFO \u7EA7\u522B\u65E5\u5FD7\u4FE1\u606F\u4E5F\u4F1A\u663E\u793A\u51FA\u6765
log4j.rootLogger=DEBUG,Console,RollingFile
#\u5C06\u65E5\u5FD7\u4FE1\u606F\u8F93\u51FA\u5230\u63A7\u5236\u53F0
log4j.appender.Console=org.apache.log4j.ConsoleAppender
log4j.appender.Console.layout=org.apache.log4j.PatternLayout
log4j.appender.Console.layout.ConversionPattern= [%-5p]-[%d{yyyy-MM-dd HH:mm:ss}] -%l -%m%n
#\u5C06\u65E5\u5FD7\u4FE1\u606F\u8F93\u51FA\u5230\u64CD\u4F5C\u7CFB\u7EDFD\u76D8\u6839\u76EE\u5F55\u4E0B\u7684log.log\u6587\u4EF6\u4E2D
log4j.appender.RollingFile=org.apache.log4j.DailyRollingFileAppender
log4j.appender.RollingFile.File=F:\\u5174\u55101903\JDBC
log4j.appender.RollingFile.layout=org.apache.log4j.PatternLayout
log4j.appender.RollingFile.layout.ConversionPattern=%d [%t] %-5p %-40.40c %X{traceId}-%m%n
db.properties：
用于存储可修改的用户名，密码，url地址
db.username=root
db.password=root
db.url=jdbc:mysql://127.0.0.1:3306/test
项目工程代码
PropertiesTool类：
用于返回用户调用时需要输入的db.properties文件中的信息。
package com.zzu.tool;
import java.io.IOException;
import java.io.InputStream;
import java.util.Properties;
public class PropertiesTool {
private static Properties properties = new Properties();
static {
InputStream inputStream = PropertiesTool.class.getClassLoader().getResourceAsStream("db.properties");//将db.properties变为javaIO流对象
try {
properties.load(inputStream);
} catch (IOException e) {
e.printStackTrace();
}
}
public static String getValue(String key) {
return properties.getProperty(key);//返回字符串key
}
}
tool包中的db包内容：
IRowMapper类：
package com.zzu.tool.db;
import java.sql.ResultSet;
public interface IRowMapper {
void rowMapper(ResultSet rs);
}
DBLink类：
package com.zzu.tool.db;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import org.apache.log4j.Logger;
/**
*数据库管理类
*
* @author WangJiaqi
*/
public class DBLink {
/**
* 使用log4jar包使得错误类型存入文件夹中
*/
private Logger logger = Logger.getLogger(DBLink.class);
/**
*获取数据库链接
*
* @author WangJiaqi
*/
private Connection getConnection() {
try {
Class.forName("com.mysql.jdbc.Driver");//加载驱动
String url = "jdbc:mysql://127.0.0.1:3306/test";
return DriverManager.getConnection(url, "root", "root");//获取连接
} catch (Exception e) {
logger.debug(e.getMessage(),e);
}
return null;
}
/**
*判断SQL能否查出数据
*
* @author WangJiaqi
*/
public boolean exist(String sql) {
Connection connection = null;
Statement statement =null;
ResultSet resultSet=null;
try {
connection = getConnection();
statement = connection.createStatement();
resultSet= statement.executeQuery(sql);//执行sql,将查询的数据存到ResultSet类型的变量中
return resultSet.next();
} catch (Exception e) {
logger.debug(e.getMessage(),e);
}finally {
close(resultSet,statement,connection);
}
return false;
}
/**
*判断SQL能否查出数据
*
* @author WangJiaqi
*/
public boolean exist(String sql,Object ...params) {
Connection connection = null;
PreparedStatement preparedStatement =null;
ResultSet resultSet=null;
try {
connection = getConnection();
preparedStatement = connection.prepareStatement(sql);
for (int i = 0; i < params.length; ++i) {
preparedStatement.setObject(i + 1, params[i]);
}
resultSet= preparedStatement.executeQuery();//执行sql,将查询的数据存到ResultSet类型的变量中
return resultSet.next();
} catch (Exception e) {
logger.debug(e.getMessage(),e);
}finally {
close(resultSet,preparedStatement,connection);
}
return false;
}
/**
*查询数据
*
* @author WangJiaqi
*/
public void select(String sql,IRowMapper rowMapper) {//接口无法创建对象，所以rowMapper参数一定指向IRowMapper接口实现类对象
Connection connection = null; //此处的rowMapper就是一个形参，到时候接口实现类里的实参再传给它
Statement statement =null;
ResultSet resultSet=null;
try {
connection = getConnection();
statement = connection.createStatement();
resultSet= statement.executeQuery(sql);//执行sql,将查询的数据存到ResultSet类型的变量中
rowMapper.rowMapper(resultSet);//因为rowMapper参数指向IRowMapper接口实现类对象，所以此处将调用接口实现类中所实现的rowMapper方法 多态
} catch (Exception e) {
logger.debug(e.getMessage(),e);
}finally {
close(resultSet,statement,connection);
}
}
/**
*查询数据
*
* @author WangJiaqi
*/
public void select(String sql,IRowMapper rowMapper,Object ...params) {//接口无法创建对象，所以rowMapper参数一定指向IRowMapper接口实现类对象
Connection connection = null; //此处的rowMapper就是一个形参，到时候接口实现类里的实参再传给它
ResultSet resultSet=null;
PreparedStatement preparedStatement = null ;
try {
connection = getConnection();
preparedStatement = connection.prepareStatement(sql);
for(int i = 0; i < params.length ; ++i) {
preparedStatement.setObject(i+1,params[i]);
}
resultSet= preparedStatement.executeQuery();
rowMapper.rowMapper(resultSet);//因为rowMapper参数指向IRowMapper接口实现类对象，所以此处将调用接口实现类中所实现的rowMapper方法 多态
} catch (Exception e) {
logger.debug(e.getMessage(),e);
}finally {
close(resultSet,preparedStatement,connection);
}
}
/**
*修改(insert，update,和delete)数据
*
* @author WangJiaqi
*/
public boolean update(String sql) {
Connection connection =null;
Statement statement = null;
try {
connection = getConnection();
statement = connection.createStatement();
int result = statement.executeUpdate(sql);
/*
statement.close();//如果上面代码出现异常，则该行代码及其下面代码无法执行，所以资源无法释放；比如sql语句语法错误，则statement和connection无法释放
connection.close();
*/
return result>0 ;
}catch(Exception e) {
logger.debug(e.getMessage(),e);
}finally {
close(statement,connection);
}
return false;
}
/**
*修改(insert，update,和delete)数据
*
* @author WangJiaqi
*/
public boolean update (String sql, Object ...params) {
Connection connection = null;
PreparedStatement prepareStatement = null;
try {
connection = getConnection();
prepareStatement = connection.prepareStatement(sql);//sql是含有？的占位符
for(int i = 0 ; i < params.length ;++i) {
prepareStatement.setObject(i+1, params[i]);//为？赋值,有几个?数字就对应几
}
return prepareStatement.executeUpdate()>0;
} catch (Exception e) {
logger.debug(e.getMessage(),e);
}finally {
close(prepareStatement,connection);
}
return false;
}
/**
*释放资源
*
* @author WangJiaqi
*/
private void close(Statement statement,Connection connection) {
try {
if(statement!=null) {//由于异常statement没有赋值，statement异常，Eg：URL出错
statement.close();
}
} catch (SQLException e) {
logger.debug(e.getMessage(),e);
}
try {
if(connection!=null) {
connection.close();
}
} catch (SQLException e) {
e.printStackTrace();
}
}
/**
* 释放资源
*
* @author WangJiaqi
*/
private void close(ResultSet resultSet,Statement statement,Connection connection) {
try {
if(resultSet!=null) {
resultSet.close();
}
} catch (SQLException e) {
logger.debug(e.getMessage(),e);
}
close(statement,connection);
}
}
Test类：
package com.zzu.test;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import com.zzu.tool.PropertiesTool;
public class Test {
public static boolean update (String sql, Object ...params) {
try {
Class.forName("com.mysql.jdbc.Driver");
String username = PropertiesTool.getValue("db.username");
String password = PropertiesTool.getValue("db.password");;
String url = PropertiesTool.getValue("db.url");;
Connection connection = DriverManager.getConnection(url, username, password);
PreparedStatement prepareStatement = connection.prepareStatement(sql);//sql是含有？的占位符
for(int i = 0 ; i < params.length ;++i) {
prepareStatement.setObject(i+1, params[i]);//为？赋值,有几个?数字就对应几
}
return prepareStatement.executeUpdate()>0;
} catch (Exception e) {
e.printStackTrace();
}
return false;
}
public static void main(String[] args) {
String sql = "delete from student where id = ?";
String str = "100' or '100'='100";
if(update(sql,str)) {
System.out.println("Yes");
}else {
System.out.println("NO");
}
}
}