之前一直纠结各种编码的却别：character_set_client character_set_connection character_set_results 还有数据库编码，表编码，字段编码
现在总结下：首先客户端发送query到服务器要通过character_set_client这个编码来编写query来发送到服务器，然后通过 character_set_connection这个编码来连接服务器。这个地方可能有些难理解，其实因为不同的编码对于校对是有区别的：举个极端的例子（只是举例使用）：譬如对于gbk的编码1<2是正确的，但是对于utf8编码就是错误的（当然这是不正确的，只是举例）， character_set_results这个的作用就是根据query查询数据库返回的数据的编码，可能数据库编码是gbk而results是utf8,那么数据库要将gbk的数据转化成utf8当然，可能转换可能会丢失那些不属于两种字符集的字符，数据库的编码作用就是存入数据库的数据的编码，当然前提是表和字段都是采取默认编码，如果表指定了编码那么就会采取表的编码，如果字段制定了编码，那么就会采用字段编码。
从上面可以看出character_set_results的返回结果与client与connection无绝对关系，这个结果主要受服务器返回的结果，然后根据结果的编码转换成character_set_results的编码
举例：
package com.service;
import java.math.BigDecimal;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Date;
public class MysqConnection {
private Connection conn = null;
//连接信息
public void getConnection() {
try {
//2005连接
Class.forName("org.gjt.mm.mysql.Driver").newInstance();
String URL = "jdbc:mysql://10.8.210.108:3306/test_character?useUnicode=true&characterEncoding=utf8&zeroDateTimeBehavior=convertToNull";
String USER = "root"; // 根据你自己设置的数据库连接用户进行设置
String PASSWORD = "1q2w3e"; // 根据你自己设置的数据库连接密码进行设置
conn = DriverManager.getConnection(URL, USER, PASSWORD);
}catch(Exception e){
e.printStackTrace();
}
}
public String getData() throws SQLException {
StringBuilder sb = new StringBuilder();
if (conn == null)
this.getConnection();
try {
String sql = "insert into test3 values('3','孙强','孙强')";
Statement stmt = conn.createStatement();
stmt.executeUpdate(sql);
int flag = 0;
ResultSet rs = stmt.executeQuery("SELECT * FROM test1") ;
while (rs.next()) {
//组装
// if(flag == 0){
// sb = new StringBuilder("insert into crm_base_data(contract_no, city,crm_code,goods_name,shop_price," +
// "orign_price,supplier_id,supplier_name,payee_name,payee_account,payee_bank,payee_sub_bank,payee_province,payee_city," +
// "payee_email,payee_mobile,jiesuan_type,operation_fee,55_foregift,logistics_foregift,service_fee,secure_funds,is_has_operation_fee,is_pre_collect_operation_fee" +
// ")values");
// }
// sb = sb.append("(").append(isNullString(rs.getString("contract_no"))).append(",").append(isNullString(rs.getString("city"))).append(",").append(isNullString(rs.getString("crm_code"))).append(",").append(isNullString(rs.getString("goods_name"))).
// append(",").append(isNullDecimal(rs.getString("shop_price"))).append(",").append(isNullDecimal(rs.getString("orign_price"))).append(",").append(isNullString(rs.getString("supplier_id"))).
// append(",").append(isNullString(rs.getString("supplier_name"))).append(",").append(isNullString(rs.getString("payee_name"))).append(",").append(isNullString(rs.getString("payee_account"))).
// append(",").append(isNullString(rs.getString("payee_bank"))).append(",").append(isNullString(rs.getString("payee_sub_bank"))).append(",").append(isNullString(rs.getString("payee_province"))).
// append(",").append(isNullString(rs.getString("payee_city"))).append(",").append(isNullString(rs.getString("payee_email"))).append(",").append(isNullString(rs.getString("payee_mobile"))).
// append(",").append((rs.getString("jiesuan_type")==null||rs.getString("jiesuan_type").length()<1)?"1":rs.getString("jiesuan_type")).append(",").append(isNullDecimal(rs.getString("operation_fee"))).append(",").
// append(isNullDecimal(rs.getString("55_foregift"))).append(",").append(isNullDecimal(rs.getString("logistics_foregift"))).append(",").append(isNullDecimal(rs.getString("service_fee"))).append(",").
// append(isNullDecimal(rs.getString("secure_funds"))).append(",").append((rs.getString("is_has_operation_fee")==null||rs.getString("is_has_operation_fee").length()<1)?"1":rs.getString("is_has_operation_fee")).append(",").
// append((rs.getString("is_pre_collect_operation_fee")==null||rs.getString("is_pre_collect_operation_fee").length()<1)?"1":rs.getString("is_pre_collect_operation_fee")).append("),");
sb = sb.append(rs.getString("cityId")).append(rs.getString("CityName")).append(rs.getString("CityType"));
}
System.out.println(sb.toString());
rs.close();
stmt.close();
}
finally {
if (conn != null)
try {
conn.close();
} catch (SQLException e) {
}
}
if(sb!=null&&sb.length()>0){
//变成 insert into ...values(),(),...();
return sb.substring(0, sb.length()-1)+";";
}
return null;
}
//字符串的如果为null或者或者空取值空字符串，否则是本身值
public String isNullString(String str){
if(str == null||str.length()<1){
return "''";
}
else
return "'"+str+"'";
}
//小数的如果为null或者空取值为0，否则是本身值
public BigDecimal isNullDecimal(String str){
if(str == null||str.length()<1){
return new BigDecimal(0);
}else{
return new BigDecimal(str);
}
}
//小数的如果为null或者空取值为0，否则是本身值
public Integer isNullInteger(String str){
if(str == null||str.length()<1){
return new Integer(0);
}else{
return Integer.valueOf(str);
}
}
public long getTimeStampNow(){
Date date = new Date();
return date.getTime();
}
public static void main(String[] args) {
MysqConnection bean = new MysqConnection();
try {
bean.getData();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
// StringBuilder sb = new StringBuilder("hello");
// System.out.println(sb.subSequence(0, sb.length()-1)+";");
// System.out.println(new BigDecimal("0.21"));
}
}