JDBC mysql 相关内容笔记

解决乱码： url字符串加上?useUnicode=true&characterEncoding=utf-8;

mysql数据库无法插入中文数据问题：将mysql数据库的编码改为utf-8;

ResultSet中get(列名)方法不一定获取的是数据库字段名，也有可能是自定义的别名，例如：select id,name,password pwd from user 此时resultSet.get("password")会抛出异常！

反射封装JDBC：

 package test;

 import java.lang.reflect.Field;
 import java.sql.Connection;
 import java.sql.DriverManager;
 import java.sql.PreparedStatement;
 import java.sql.ResultSet;
 import java.sql.ResultSetMetaData;
 import java.sql.SQLException;
 import java.util.ArrayList;
 import java.util.List;

 public class TestReflectionJDBC<T> {

     private static Connection connection = null;
     private static PreparedStatement preparedStatement = null;
     private static ResultSet resultSet = null;

     private Connection getConnection() {
         try {
             Class.forName("com.mysql.jdbc.Driver");
             if (connection == null) {
                 connection = DriverManager.getConnection(
                         "jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=utf-8", "root", "123456");
             }
         } catch (Exception e) {
             e.printStackTrace();
         }
         return connection;
     }    

     public List<T> query(String sql,Class<T> clzz,Object...objects){
         List<T> list=new ArrayList<>();
         try {
             preparedStatement=getConnection().prepareStatement(sql);
             for(int i = 0;i<objects.length;i++){
                 preparedStatement.setObject(i+1, objects[i]);
             }
             resultSet=preparedStatement.executeQuery();
             if(resultSet!=null){
                 ResultSetMetaData resultSetMetaData=null;
                 while(resultSet.next()){
                     //if(resultSetMetaData==null){
                         resultSetMetaData=resultSet.getMetaData();
                         T t=clzz.newInstance();
                         int count=resultSetMetaData.getColumnCount();
                         for(int i=0;i<count;i++){
                             String name=resultSetMetaData.getColumnName(i+1);
                             Field field=clzz.getDeclaredField(name);
                             field.setAccessible(true);
                             Object value=resultSet.getObject(name);
                             field.set(t, value);
                         }
                         list.add(t);
                     //}
                 }
             }
         } catch (Exception e) {
             e.printStackTrace();
         }
         return list;
     }
     public int update(String sql,Object...objects){
         int result=0;
         try {
             preparedStatement=getConnection().prepareStatement(sql);
             for(int i=0;i<objects.length;i++){
                 preparedStatement.setObject(i+1, objects[i]);
             }
             result=preparedStatement.executeUpdate();
         } catch (SQLException e) {
             e.printStackTrace();
         }
         return result;
     }
 }