MySQL database operations

Package cn.com. vanos. DB; import Java. SQL. connection; import Java. SQL. drivermanager; import Java. SQL. resultset; import Java. SQL. sqlexception; import Java. SQL. statement; import Java. util. arraylist; import Java. util. hashmap; import Java. util. iterator; import Java. util. list; import Java. util. map; import Java. util. set; import Java. util. map. entry; import javax. XML. registry. deleteexception; public class dbmanager {Publ IC static string dbname = "vanos"; static connection conn = NULL; Public synchronized static connection openconnection () {try {class. forname ("com. mySQL. JDBC. driver "); string url =" JDBC: mysql: // 127.0.0.1: 3306/"+ dbname + "? Useunicode = true & characterencoding = UTF-8 "; Conn = drivermanager. getconnection (URL, "root", "root");} catch (exception e) {system. out. println ("exception:" + E. getmessage ();} return conn;} public static void main (string [] ARGs) throws sqlexception {openconnection (); // resultset rs = execsql ("describe t_user "); // Rs. next (); // system. out. println (RS. getstring ("field"); // select ("t_user", 2nd); // Select page, the maximum size of each page Value: 3 // selectpage ("t_user", 2, 3); // Getline ("t_user", "id = '1 '"); // Getline ("t_user", "username = 'hangzhou'"); // hashmap map = Getline ("t_user", "id = '8 '"); // map. put ("password", "12"); // Update ("t_user", map, "id = '8'"); Delete ("t_user ", "username = 'renwang'"); closeconn ();} Private Static Boolean execute (string SQL) {try {statement stat = Conn. createstatement (); system. out. print ("SQL:" + SQL); boo Lean ret = stat.exe cute (SQL); system. out. println ("[" + stat. getupdatecount () + "row (s) affected]");} catch (sqlexception e) {e. printstacktrace ();} return false;} public static void Delete (string table, string whereclause) {execute ("delete from" + Table + "where" + whereclause );} // update 'vanos '. 't_ user' // set 'email '= 'wac2056 @ 163.com', 'phonenum' = '000000' // Where 'id' = '8'; public static voi D Update (string table, hashmap tablevalues, string whereclause) {string sqlvalues = ""; set <entry <string, Object> entryset = tablevalues. entryset (); For (iterator <entry <string, Object> itr = entryset. iterator (); itr. hasnext ();) {entry = itr. next (); sqlvalues + = entry. getkey () + "= '" + entry. getvalue () + "',";} sqlvalues = sqlvalues. substring (0, sqlvalues. length ()-1); execute ("Update" + Table + "Set" + sqlvalues + "where" + whereclause);} // insert into 't_ user' ('id', 'username', 'Password', 'email ', 'phonenum') // values (1, 'renwang', '000000', 'wac056 @ 163.com ', '000000') public static void add (string table, hashmap tablevalues) {string sqlvalues = ""; string sqlfields = ""; set <entry <string, Object> entryset = tablevalues. entryset (); For (iterator <entry <string, Object> itr = entryset. iterato R (); itr. hasnext ();) {entry = itr. next (); sqlfields + = "'" + entry. getkey () + "',"; sqlvalues + = "'" + entry. getvalue () + "',";} sqlfields = sqlfields. substring (0, sqlfields. length ()-1); sqlvalues = sqlvalues. substring (0, sqlvalues. length ()-1); execute ("insert into" + Table + "(" + sqlfields + ") values (" + sqlvalues + ")");} /***** @ Param table name * @ Param curpage current page number * @ Param Maxitemsizethe size that a page contain * @ Param fieldswhat fields of table you want to get. */public static list selectpage (string table, int curpage, int maxitemsize, string... fields) throws sqlexception {return select (table, (curPage-1) * maxitemsize, (curpage) * maxitemsize, fields);} public static list select (string table, int min, int Max, string... fields) throws sqlexception {stri Ng filed2sql = ""; if (fields. length = 0) {filed2sql = "*";} else {for (string field: fields) {filed2sql + = "" + field + ",";} If (filed2sql! = NULL) filed2sql = filed2sql. substring (0, filed2sql. length ()-1);} resultset rs = execsql ("select" + filed2sql + "from" + Table + "Limit" + min + "," + max ); list