数据库连接及操作

     设置静态连接参数，然后设置路径，加载驱动，返回一个连接对象。

package com.weixin.javabean;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.SQLException;
import java.sql.Statement;

public class DBConf {
private static final String url = "jdbc:mysql://33333/HAHAH?useUnicode=true&characterEncoding=UTF-8&autoReconnect=true";
private static final String name = "com.mysql.jdbc.Driver";
private static final String user = "root";
private static final String password = "123456";
private static Connection conn=null;

public static Connection getConn() {
try {
Class.forName(name);
return DriverManager.getConnection(url, user, password);  //调用方法返回一个连接对象
} catch (Exception e) {
e.printStackTrace();
}
return null;
}

}

数据库操作：主要注意操作对象为harshtable列表，利用迭代进行sql的拼接，i="1'，为标志性，使循环执行一次，数据url拼接好后，进行数据库操作，注意try ,catch抓错。注意：只进行了一次数据库连接，只产生了一个数据库连接对象，所有的数据库操作都只利用这一个，

package com.weixin.util;

import java.lang.reflect.Field;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Hashtable;
import java.util.Iterator;
import java.util.List;

import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.MapListHandler;
import org.stringtree.json.JSONValidatingWriter;

import com.google.gson.Gson;
import com.google.gson.reflect.TypeToken;
import com.weixin.javabean.DBConf;
import com.weixin.javabean.UserInfo;

public class DBUtil {
private static Connection conn = DBConf.getConn();
private static Statement stat = null;
private static ResultSet rs = null;
private static String sql=null;
private static Hashtable <String,String>list=new Hashtable<String,String>();
private static Gson gson=new Gson();
/*public static Connection getCon()//需要多个连接对象时
{
cout++;
if(count%3==0)
return conn;
else if(count%3==1)
return conn1;
else if(count%3==2)
return conn2;
}*/
/**
* 功能：数据库插入操作
* @param ht 存储字段信息的hashtable 存储格式(Hashtable)ht.put(字段名，字段值);
* @param tablename 操作的数据库表名
* @return 返回json格式的执行信息
*/
public static  String insert(Hashtable ht, String tablename) {
String before_sql, after_sql;
before_sql = "insert into " + tablename + "(";
after_sql = " values('";
int i = 1;
for (Iterator iter = ht.keySet().iterator(); iter.hasNext(); i = 0) {
String key = (String) iter.next();
Object value =  ht.get(key);
if (i != 1) {
before_sql += ",";
after_sql += "','";
}
before_sql += key;
after_sql += value;
}
sql = before_sql + ")" + after_sql + "')";

lo
4000
gout.ps.println("insert sql:" + sql);

try {

stat = conn.createStatement();
list.put("errorcode", stat.executeUpdate(sql)+"");
list.put("errmsg", "ok");
return gson.toJson(list);
} catch (SQLException e) {
// TODO Auto-generated catch block

e.printStackTrace(logout.ps);

list.put("errorcode", "-1");
list.put("errmsg", e.toString());

e.printStackTrace();
return gson.toJson(list);

}

}

/**
*
* 功能：查询数据库 （注意：返回记录哪怕只有一条也是用json数组存放的，即用[]括起来的）
* @param ht Hashtable对象，其中存放sql查询条件
* @param tablename  带查询表名
* @return 返回json格式的字符串
*/
public static String select(Hashtable ht, String tablename) {
String sql;
sql = "select * from " + tablename;
int i = 1;
for (Iterator iter = ht.keySet().iterator(); iter.hasNext(); i = 0) {
String key = (String) iter.next();
Object value = ht.get(key);
if (i == 1) {
sql += " where ";
} else {
sql += " and ";
}
sql += key + "='" + value+"'";
}

logout.ps.println("select sql:" + sql);

try {
String json = new JSONValidatingWriter().write(new QueryRunner().query(conn, sql, new MapListHandler()));
return json;
} catch (SQLException e) {
// TODO Auto-generated catch block

e.printStackTrace(logout.ps);

e.printStackTrace();
}
return null;
}

/**
* 功能：数据库更新操作
* @param ht 待更新的数据信息，包括查询条件
* @param tablename 操作的数据库表
* @param id 查询条件的字段名
* @return 返回json格式的执行情况
*/
public static String update(Hashtable ht, String tablename,String id){
String before_sql, after_sql, sql;
before_sql = "update " + tablename + " set ";
after_sql = " where ";
int i = 1;
for (Iterator iter = ht.keySet().iterator(); iter.hasNext(); ) {
String key = (String) iter.next();
Object value =  ht.get(key);

if(key.equals(id))
{
after_sql+=key+ "='" + value+"'";
}else
{
if (i != 1) {
before_sql += " , ";
}
before_sql += key+ "='" + value+"'";
i=0;
}
}
sql = before_sql +  after_sql;

logout.ps.println("update sql:" + sql);

try {
stat = conn.createStatement();
list.put("errorcode", stat.executeUpdate(sql)+"");
list.put("errmsg", "ok");
return gson.toJson(list);
} catch (SQLException e) {

e.printStackTrace(logout.ps);

// TODO Auto-generated catch block
e.printStackTrace();
list.put("errorcode", "-1");
list.put("errmsg", e.toString());
return gson.toJson(list);
}

}

/**
* @param ht 删除条件
* @param tablename 数据库表名
* @return 返回操作情况  0失败
*/
public static int delete(Hashtable ht, String tablename){
String before_sql, after_sql, sql;
sql = "delete from " + tablename + " where ";
int i = 1;
for (Iterator iter = ht.keySet().iterator(); iter.hasNext();i=0 ) {
String key = (String) iter.next();
Object value =  ht.get(key);

if (i != 1) {
sql += " and ";
}
sql += key+ "='" + value+"'";
}

logout.ps.println("delete sql:" + sql);

try {
stat = conn.createStatement();

return stat.executeUpdate(sql);
} catch (SQLException e) {

e.printStackTrace(logout.ps);

// TODO Auto-generated catch block
e.printStackTrace();
return -1;
}
}

/**
* 获取表中最大的主键值
* @param tablename 数据库表名
* @param id 主键字段名
* @return 最大的主键值
*/
public static String getNextID(String tablename,String id) {
sql="select MAX("+id+") as "+id+" from "+tablename;

logout.ps.println("sql:"+sql);
try {
String json = new JSONValidatingWriter().write(new QueryRunner().query(conn, sql, new MapListHandler()));

logout.ps.println("json:"+json);
json=json.replace("[", "");
json=json.replace("]", "");
Hashtable<String,Double> ht=gson.fromJson(json, Hashtable.class);
double d=ht.get(id);

logout.ps.println("ht:"+(int)d+"");

return  (int)d+"";
} catch (SQLException e) {

e.printStackTrace(logout.ps);

// TODO Auto-generated catch block
e.printStackTrace();
}
return null;
}

/**
* @param sql 查询sql语句
* @return json格式的结果集
*/
public static String select(String sql) {

logout.ps.println("DBUtil seleclt(sql):"+sql);

try {
String json = new JSONValidatingWriter().write(new QueryRunner().query(conn, sql, new MapListHandler()));
return json;
} catch (SQLException e) {

e.printStackTrace(logout.ps);

// TODO Auto-generated catch block
e.printStackTrace();
}
return null;
}

/**
* @param sql 更新，删除sql语句
* @return 返回操作情况
*/
public static String update(String sql) {

logout.ps.println("user defined update sql:"+sql);

try {
stat = conn.createStatement();
list.put("errorcode", stat.executeUpdate(sql)+"");
list.put("errmsg", "ok");
return gson.toJson(list);
} catch (SQLException e) {

e.printStackTrace(logout.ps);

// TODO Auto-generated catch block
e.printStackTrace();
}
return null;
}

public static void main(String[] args) {
Hashtable ht = new Hashtable();
String str=select(ht,"BillInfo");
str="\"rows\":"+str;
System.out.println(str);

}
}