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(); } } /** * 执行一条查询sql,以 List<hashmap> 的形式返回查询的记录，记录条数，和从第几条开始，由参数决定，主要用于翻页 * pageno 页码 rowsize 每页的条数 */ 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
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