package dao;import java.io.FileInputStream;import java.io.IOException;import java.io.InputStream;import java.sql.Connection;import java.sql.DriverManager;import java.sql.ResultSet;import java.sql.ResultSetMetaData;import java.sql.SQLException;import java.sql.Statement;import java.util.ArrayList;import java.util.Collection;import java.util.Date;import java.util.HashMap;import java.util.Iterator;import java.util.List;import java.util.Map;import java.util.Properties;import javax.servlet.ServletContext;public class CommDAO{?? ??? ?Connection conn = null;?? ??? ?public CommDAO()?? ?{?? ??? ?conn = this.getConn();?? ?}?? ?private static Properties config = null;?? ? static {?? ??? ? try {?? ??? ??? ??? ?? config = new Properties(); ?? ?? // InputStream in = config.getClass().getResourceAsStream("dbconnection.properties");?? ????? InputStream in =? CommDAO.class.getClassLoader().getResourceAsStream("dbconnection.properties");? ?? ??? config.load(in);?? ? ??? ??? in.close();?? ?? } catch (Exception e) {?? ?? e.printStackTrace();?? ?? }?? ? }?? ?public Connection getConn()?? ?{?? ???????? try?? ???????? {?? ??????? ??? ?String d = new Date().toLocaleString().substring(0,9);?? ?????????? ??? ??????? ??? ?? Class.forName("com.mysql.jdbc.Driver");?? ???????????? String dburl = (String)config.get("dburl");?? ???????????? conn = DriverManager.getConnection(dburl);?? ??????? ??? ??? ???????? }?? ???????? catch(Exception e)?? ???????? {?? ???????????? e.printStackTrace();?? ???????? }?? ???????? return conn;?? ?}?? ??? ??? ?public int getInt(String sql)?? ?{?? ??? ?int i = 0;?? ??? ?try {?? ??? ??? ?Statement st = conn.createStatement();?? ??? ??? ?ResultSet rs = st.executeQuery(sql);?? ??? ??? ?if(rs.next())?? ??? ??? ?{?? ??? ??? ??? ?i = rs.getInt(1);?? ??? ??? ?}?? ??? ??? ???? st.close();?? ??? ?} catch (SQLException e) {?? ??? ??? ?// TODO Auto-generated catch block?? ??? ??? ?e.printStackTrace();?? ??? ?}?? ??? ?return i;?? ?}?? ??? ??? ?public double getDouble(String sql)?? ?{?? ??? ?double i = 0;?? ??? ?try {?? ??? ??? ?Statement st = conn.createStatement();?? ??? ??? ?ResultSet rs = st.executeQuery(sql);?? ??? ??? ?if(rs.next())?? ??? ??? ?{?? ??? ??? ??? ?i = rs.getDouble(1);?? ??? ??? ??? ??? ??? ??? ?}?? ??? ??? ???? st.close();?? ??? ?} catch (SQLException e) {?? ??? ??? ?// TODO Auto-generated catch block?? ??? ??? ?e.printStackTrace();?? ??? ?}?? ??? ?return i;?? ?}?? ??? ?public void commOper(String sql)?? ?{?? ??? ?try {?? ??? ??? ?Statement st = conn.createStatement();?? ??? ???? st.execute(sql);?? ??? ???? st.close();?? ??? ?} catch (SQLException e) {?? ??? ??? ?// TODO Auto-generated catch block?? ??? ??? ?e.printStackTrace();?? ??? ?}?? ?}?? ??? ?public void commOperSqls(ArrayList<String> sql)?? ?{?? ??? ??? ??? ?try {?? ??? ??? ?conn.setAutoCommit(false);?? ??? ??? ?for(int i=0;i<sql.size();i++)?? ??? ??? ?{?? ??? ??? ?Statement st = conn.createStatement();?? ??? ??? ??? ??? ???? st.execute(sql.get(i));?? ??? ???? st.close();?? ??? ??? ?}?? ??? ??? ?conn.commit();?? ??? ?} catch (SQLException e) {?? ??? ??? ?try {?? ??? ??? ??? ?conn.rollback();?? ??? ??? ?} catch (SQLException e1) {?? ??? ??? ??? ?e1.printStackTrace();?? ??? ??? ?}?? ??? ??? ?e.printStackTrace();?? ??? ?}finally{?? ??? ??? ?try {?? ??? ??? ??? ?conn.setAutoCommit(true);?? ??? ??? ?} catch (SQLException e) {?? ??? ??? ??? ?e.printStackTrace();?? ??? ??? ?}?? ??? ?}?? ?}?? ??? ??? ?public List<HashMap> select(String sql)?? ?{?? ??? ?List<HashMap> list = new ArrayList();?? ??? ?try {?? ??? ??? ?Statement st = conn.createStatement();?? ??? ???? ResultSet rs = st.executeQuery(sql);?? ??? ???? ResultSetMetaData rsmd = rs.getMetaData();????????? ??? ??? ???? while(rs.next())?? ??? ???? {?? ??? ??? ??? ?HashMap map = new HashMap();?? ??? ??? ??? ?int i = rsmd.getColumnCount();?? ??? ??? ??? ?for(int j=1;j<=i;j++)?? ??? ??? ??? ?{?? ??? ??? ??? ??? ?if(!rsmd.getColumnName(j).equals("ID"))?? ??? ??? ??? ??? ?{?? ??? ??? ??? ??? ??? ??? ??? ??? ?map.put(rsmd.getColumnName(j), rs.getString(j)==null?"":rs.getString(j));?? ??? ??? ??? ??? ?}?? ??? ??? ??? ??? ?else?? ??? ??? ??? ??? ?{?? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ?map.put("id", rs.getString(j));?? ??? ??? ??? ??? ?}?? ??? ??? ??? ?}?? ??? ??? ??? ?list.add(map);?? ??? ???? }?? ??? ???? rs.close();?? ??? ???? st.close();?? ??? ?} catch (SQLException e) {?? ??? ??? ?// TODO Auto-generated catch block?? ??? ??? ?System.out.println("--"+sql);?? ??? ??? ?e.printStackTrace();?? ??? ?}?? ??? ?return list;?? ?}?? ??? ??? ?public void close()?? ?{?? ??? ?try {?? ??? ??? ?conn.close();?? ??? ?} catch (SQLException e) {?? ??? ??? ?// TODO Auto-generated catch block?? ??? ??? ?e.printStackTrace();?? ??? ?}?? ?}?? ??? ?/**?? ? * 執(zhí)行一條查詢sql,以 List<hashmap> 的形式返回查詢的記錄，記錄條數(shù)，和從第幾條開始，由參數(shù)決定，主要用于翻頁?? ? * pageno 頁碼? rowsize 每頁的條數(shù)?? ? */?? ?public List select(String sql, int pageno, int rowsize) {?? ??? ?List<HashMap> list=new ArrayList<HashMap>();?? ??? ?List<HashMap> mlist=new ArrayList<HashMap>();?? ??? ?try{?? ??? ??? ?list=this.select(sql);?? ??? ??? ?int min = (pageno-1)*rowsize;?? ??? ??? ?int max = pageno*rowsize;?? ??? ??? ??? ??? ??? ?for(int i=0;i<list.size();i++)?? ??? ??? ?{?? ??? ??? ??? ??? ??? ??? ??? ?if(!(i<min||i>(max-1)))?? ??? ??? ??? ?{?? ??? ??? ??? ?mlist.add(list.get(i));?? ??? ??? ??? ?}?? ??? ??? ?}?? ??? ?}catch(RuntimeException re){?? ??? ??? ?re.printStackTrace();?? ??? ??? ?throw re;?? ??? ?}????? ?? ??? ?return mlist;?? ?}?? ?public static void main(String[] args) {?? ??? ?System.out.println(new CommDAO());?? ?}}java.sql.SQLException: The url cannot be null?? ?at java.sql.DriverManager.getConnection(DriverManager.java:649)?? ?at java.sql.DriverManager.getConnection(DriverManager.java:270)?? ?at dao.CommDAO.getConn(CommDAO.java:66)?? ?at dao.CommDAO.<init>(CommDAO.java:31)?? ?at org.apache.jsp.welcome_jsp._jspService(welcome_jsp.java:124)?? ?at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)?? ?at javax.servlet.http.HttpServlet.service(HttpServlet.java:731)?? ?at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:439)?? ?at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:395)?? ?at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:339)?? ?at javax.servlet.http.HttpServlet.service(HttpServlet.java:731)?? ?at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)?? ?at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)?? ?at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)?? ?at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)?? ?at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)?? ?at util.SetChar.doFilter(SetChar.java:26)?? ?at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)?? ?at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)?? ?at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:218)?? ?at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)?? ?at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:505)?? ?at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:169)?? ?at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)?? ?at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:958)?? ?at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)?? ?at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:452)?? ?at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1087)?? ?at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:637)?? ?at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:316)?? ?at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)?? ?at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)?? ?at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)?? ?at java.lang.Thread.run(Thread.java:745)六月 12, 2017 2:06:37 下午 org.apache.catalina.core.ApplicationContext log信息: java.lang.NullPointerException