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;
    }
}