1.dbcp连接数据库（附带基本数据库操作方法）
package com.nplus.dbcp; import java.io.InputStream; import java.sql.Connection; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.ResultSetMetaData; import java.sql.SQLException; import java.sql.Statement; import java.util.ArrayList; import java.util.HashMap; import java.util.List; import java.util.Map; import java.util.Properties; import org.apache.commons.dbcp.BasicDataSource; import org.apache.commons.dbcp.BasicDataSourceFactory; import org.apache.log4j.Logger; import com.nplus.help.StringHelper; public class Dbcp { public static Logger logger = Logger.getLogger(Dbcp.class); private static final String config = "commons-dbcp.properties"; private BasicDataSource ds; private static Dbcp db; private Connection conn = null; private Statement stmt = null; private Dbcp(String config) { this.ds = null; try { this.ds = createDataSource(config); } catch (Throwable thr) { throw new RuntimeException(thr); } } public synchronized static Dbcp getInstance() { if (db == null) try { db = new Dbcp(config); } catch (Exception e) { e.printStackTrace(); } return db; } public static BasicDataSource createDataSource(String propertiesFile) throws Exception { Properties properties = new Properties(); // System.out.println("dbcp // path="+Dbcp.class.getResource(".").getPath()); InputStream stream = Dbcp.class.getResourceAsStream(propertiesFile); properties.load(stream); stream.close(); BasicDataSource ds = (BasicDataSource) BasicDataSourceFactory .createDataSource(properties); return ds; } public Connection getConnection() throws SQLException { return this.ds.getConnection(); } public static void close(Connection conn) { if (conn != null) try { conn.close(); } catch (Throwable localThrowable) { } } public static void close(Statement stmt) { if (stmt != null) try { stmt.close(); } catch (Throwable localThrowable) { } } public static void close(ResultSet rs) { if (rs != null) try { rs.close(); } catch (Throwable localThrowable) { } } public static void close(Connection conn, Statement stmt, ResultSet rs) { close(rs); close(stmt); close(conn); } public static void close(Connection conn, Statement stmt) { close(stmt); close(conn); } public static void close(Statement stmt, ResultSet rs) { close(rs); close(stmt); } public int getExecuteCount(String sql) { int queryNum = -1; ResultSet rs = null; Connection conn = null; Statement stmt = null; try { conn = this.getConnection(); stmt = conn.createStatement(); rs = stmt.executeQuery(sql); if (rs != null) { rs.next(); queryNum = rs.getInt(1); } } catch (Exception e) { e.printStackTrace(); logger.info(sql); } finally { closeAll(conn, rs, stmt); } return queryNum; } public int getExecuteCount(String sql,Object[] params) { int queryNum = -1; ResultSet rs = null; Connection conn = null; PreparedStatement ps = null; try { conn = this.getConnection(); ps = conn.prepareStatement(sql); for(int i=0;i<params.length;i++) { ps.setObject(i+1, params[i]); } rs = ps.executeQuery(); if (rs != null) { rs.next(); queryNum = rs.getInt(1); } } catch (Exception e) { e.printStackTrace(); logger.info(new StringHelper().getSql(sql, params)); } finally { closeAll(conn, rs, stmt); } return queryNum; } public void closeAll(Connection conn, ResultSet rs, Statement stmt) { close(conn); close(rs); close(stmt); } public String getNextSequence(String seq_name) { String sql = "select " + seq_name + ".nextval seq_value from dual"; Map map = db.getValue(sql); return (String) map.get("SEQ_VALUE"); } public String getStringValue(String sql) { Map map = db.getValue(sql); return (String) map.get("STRING_VALUE"); } public int execute(String sqlstr) { ResultSet rs = null; Connection conn = null; Statement stmt = null; try { conn = getConnection(); stmt = conn.createStatement(); stmt.execute(sqlstr); return 1; } catch (Exception e) { e.printStackTrace(); logger.info(sqlstr); } finally { closeAll(conn, rs, stmt); } return 0; } public int execute(String sql,Object[] params) { ResultSet rs = null; Connection conn = null; PreparedStatement ps = null; try { conn = getConnection(); ps = conn.prepareStatement(sql); for(int i=0;i<params.length;i++) { ps.setObject(i+1, params[i]); } ps.execute(); return 1; } catch (Exception e) { e.printStackTrace(); logger.info(new StringHelper().getSql(sql, params)); } finally { closeAll(conn, rs, ps); } return 0; } public ArrayList getList(String sqlString) { ArrayList<Map> pkv = new ArrayList<Map>(); ResultSet rs = null; Connection conn = null; Statement stmt = null; try { conn = getConnection(); stmt = conn.createStatement(); rs = stmt.executeQuery(sqlString); ResultSetMetaData rsmd = rs.getMetaData(); int num = rsmd.getColumnCount(); while (rs.next()) { Map map = new HashMap(); for (int i = 1; i <= num; i++) { String key = rsmd.getColumnName(i); String value = rs.getString(i); if (value == null) value = ""; map.put(key, value); } pkv.add(map); } } catch (SQLException e) { logger.error(sqlString); logger.error(e.toString()); } finally { closeAll(conn, rs, stmt); } return pkv; } public Map getValue(String sql) { Map map = new HashMap(); ResultSet rs = null; Connection conn = null; Statement stmt = null; try { conn = getConnection(); stmt = conn.createStatement(); rs = stmt.executeQuery(sql); ResultSetMetaData rsmd = rs.getMetaData(); int num = rsmd.getColumnCount(); if (rs.next()) { for (int i = 1; i <= num; i++) { String key = rsmd.getColumnName(i); String value = rs.getString(i); if (value == null) value = ""; map.put(key, value); } } } catch (Exception e) { logger.info(sql); logger.info(e.toString()); } finally { closeAll(conn, rs, stmt); } return map; } public int excuteBatch(List<String> sqlList) { Connection conn = null; Statement stmt = null; try { conn = getConnection(); conn.setAutoCommit(false); stmt = conn.createStatement(); for (String sql : sqlList) { stmt.addBatch(sql); } stmt.executeBatch(); conn.commit(); conn.setAutoCommit(true); return 1; } catch (Exception e) { e.printStackTrace(); try { if (stmt != null) { stmt.close(); stmt = null; } if (conn != null) { conn.close(); conn = null; } } catch (SQLException ee) { logger.info(ee.toString()); } } finally { try { if (stmt != null) { stmt.close(); stmt = null; } if (conn != null) { conn.close(); conn = null; } } catch (SQLException ee) { logger.info(ee.toString()); } } return 0; } public void beginBatch() { try { conn = getConnection(); conn.setAutoCommit(false); stmt = conn.createStatement(); } catch (Exception e) { e.printStackTrace(); try { if (stmt != null) { stmt.close(); stmt = null; } if (conn != null) { conn.close(); conn = null; } } catch (SQLException ee) { // TODO Auto-generated catch block logger.info(e.toString()); } } } public void addBatch(String sql) { try { stmt.addBatch(sql); } catch (SQLException e) { e.printStackTrace(); try { if (stmt != null) { stmt.close(); stmt = null; } if (conn != null) { conn.close(); conn = null; } } catch (SQLException ee) { ee.printStackTrace(); } } } public int doBatch() { try { stmt.executeBatch(); conn.commit(); return 1; } catch (SQLException e) { e.printStackTrace(); try { conn.rollback(); if (stmt != null) { stmt.close(); stmt = null; } if (conn != null) { conn.close(); conn = null; } } catch (SQLException ee) { logger.info(ee.toString()); } } return 0; } public void endBatch() { try { if (stmt != null) { stmt.close(); stmt = null; } if (conn != null) { conn.close(); conn = null; } } catch (SQLException e) { e.printStackTrace(); } } }
在servlet中 private Dbcp db = Dbcp.getInstance(); 之后 就可以使用db里面的方法。
2.servlet中实现ajax交互
前端页面
<form id="adminForm"> <div class="inputArea"> <label>旧密码:</label> <div class="inputLine"><input value="" placeholder="旧密码" type="password" name="password" placeholder="请输入旧密码" id="password"></div> </div> <div class="inputArea"> <label>新密码:</label> <div class="inputLine"><input value="" placeholder="新密码" type="password" name="newPwd" placeholder="请输入新密码" id="newPwd"></div> </div> <div class="inputArea"> <label>再次输入新密码:</label> <div class="inputLine"><input value="" placeholder="再次输入新密码" type="password" name="newPwd2" placeholder="请再次输入新密码" id="newPwd2"></div> </div> </form>
前端jQuery
var state=0;
var pwd = $("#password").val();
if(pwd != null && $.trim(pwd) !=""){ $.ajax({ type:"POST", async:false, url:"${ctx }/admin/audit.json", data:{password:pwd}, success:function(result){ result = eval("("+result+")"); if(result.status == "true" || result.status == true){ state=1; }else{ state=0; if(result.flag == '请先登录再操作'){ alert("请先登录再操作"); window.location.href="${ctx}/admin/login.html"; }else{ alert(result.flag); } } } }); }else{ alert("请输入旧密码"); return false; }
后台java代码
public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { String password = request.getParameter("password"); response.setContentType("text/html;charset=UTF-8"); response.setHeader("Cache-Control","no-cache"); JSONObject json = new JSONObject(); json.put("status", false); String str = (String)request.getSession().getAttribute("SESSION_ADMIN"); if(str != null){ String sqlById = "select * from t_admin where id="+str; Map<String, String> map = db.getValue(sqlById); if(map != null && StringUtils.isNotBlank(map.get("username"))){ if(StringUtils.isNotBlank(map.get("password"))){ if(map.get("password").equals(new MD5Util().MD5(password))){ json.put("status", true); json.put("flag", "旧密码验证成功"); response.getWriter().write(json.toString()); return; }else{ json.put("flag", "旧密码验证失败"); response.getWriter().write(json.toString()); return; } } }else{ json.put("flag", "请先登录再操作"); response.getWriter().write(json.toString()); return; } }else{ json.put("flag", "请先登录再操作"); response.getWriter().write(json.toString()); return; } }
3.request.getRequestDispatcher response.sendRedirect区别，以及文件路径和跳转路径区别（原文链接：http://blog.csdn.net/honglei_zh/article/details/7204946）
response.sendRedirect(url) -- 重定向到指定URL
request.getRequestDispatcher(url).forward(request,response) -- 请求转发到指定URL
二者区别：
response.sendRedirect(url)跳转到指定的URL地址，产生一个新的request，所以要传递参数只有在url后加参数，如：
url?id=1.
request.getRequestDispatcher(url).forward(request,response)
是直接将请求转发到指定URL，所以该请求能够直接获得上一个请求的数据，也就是说采用请求转发，request对象始终存在，不会重新创建。而
sendRedirect()会新建request对象，所以上一个request中的数据会丢失。
更具体来说就是这样的：
redirect 会首先发一个response给浏览器, 然后浏览器收到这个response后再发一个requeset给服务器, 然后服务器发新的response给浏览器. 这时页面收到的request是一个新从浏览器发来的.
forward 发生在服务器内部, 在浏览器完全不知情的情况下发给了浏览器另外一个页面的response. 这时页面收到的request不是从浏览器直接发来了,可能己经用request.setAttribute在request里放了数据.在转到的页面可 直接用request.getAttribute获得数据。
最基本的用法就如上了，其他的一些应注意的地方如下：
跳转方式
运用forward方法只能重定向到同一个Web应用程序中的一个资源。而sendRedirect方法可以让你重定向到任何URL。
表单form的action="/uu";sendRedirect("/uu");表示相对于服务器根路径。如http://localhost:8080/Test 应用（则提交至http://localhost:8080/uu ）;
Forward代码中的"/uu"则代表相对与WEB应用的路径。如http://localhost:8080/Test 应用（则提交至http://localhost:8080/Test/uu ）;
（运用RequestDispatcher接口的Forward）方法
forward()无法重定向至有frame的jsp文件,可以重定向至有frame的html文件,
同时forward()无法在后面带参数传递,比如servlet?name=frank,这样不行,可以程序内通过response.setAttribute("name",name)来传至下一个页面.
"/"代表相对与web应用路径
RequestDispatcher rd = request.getRequestDispatcher("/ooo");
rd.forward(request, response);提交至http://localhost:8080/Test/ooo
RequestDispatcher rd = getServletContext().getRequestDispatcher("/ooo");
rd.forward(request, response);提交至http://localhost:8080/Test/ooo
RequestDispatcher rd =getServletContext().getNamedDispatcher("TestServlet");（TestServlet为一个<servlet-name>）
rd.forward(request, response);提交至名为TestServlet的servlet
如果在<jsp:forward>之前有很多输出,前面的输出已使缓冲区满,将自动输出到客户端,那么该语句将不起作用,这一点应该特别注意。
另外要注意：它不能改变浏览器地址，刷新的话会导致重复提交
从http://localhost:8080/Test/gw/page.jsp 中转发
<jsp:forward page="OtherPage.jsp"/>在JSP页面被解析后转换成pageContext.forward("OtherPage.jsp");
"/OtherPage.jsp"提交到http://localhost:8080/Test/OtherPage.jsp
"OtherPage.jsp"提交到http://localhost:8080/Test/gw/OtherPage.jsp
(运用HttpServletResponse接口的sendRedirect）方法302
是在用户的浏览器端工作,sendRedirect()可以带参数传递,比如servlet?name=frank传至下个页面,
同时它可以重定向至不同的主机上,sendRedirect()可以重定向有frame.的jsp文件.
假设转发代码包含于注册的servlet－url为/ggg/tt;jsp为/ggg/tt.jsp:
绝对路径：response.sendRedirect("http://www.brainysoftware.com
根路径：response.sendRedirect("/ooo")发送至http://localhost:8080/ooo
相对路径：response.sendRedirect("ooo")发送至http://localhost:8080/Test/ggg/ooo ,
sendRedirect等同于此方式
response.setStatus(HttpServletResponse.SC_MOVED_PERMANENTLY);
String newLocn = "/newpath/jsa.jsp";
response.setHeader("Location",newLocn);
路径资料来源（http://blog.csdn.net/m1872216/article/details/7913658）
服务器端的相对路径 、绝对路径
相对*.do，绝对/*.do；
DD（web.xml）文件中的url-pattern只能绝对路径，即/*.do，根地址为应用目录。
- <form action=”" >中的路径一般写相对，即为DD文件中定义的servlet-mapping的url-pattern。例如DD中<url- pattern>/proName</url-pattern>，action=”proName”。若action要写绝对地址，则 必须从服务器根写起，因为container是从server开始分析的。例如action=”/webapp/proName”。
- HttpServletResponse.sendRedirect(String)
参数可以指定为相对路径：response.sendRedirect(“/foo/stuff.do”)。容器相对于Web应用本身加参数建立完整的URL—http://localhost/foo/stuff.do。
其它Web应用：相对路径或绝对路径。
相对路径情况下生成的完整URL与sendRedirect方法相同。
绝对路径与重定向不同，容器将相对于Web应用的根目录加参数生成完整的URL，即：request.getRequestDispatcher(“/foo/stuff.do”)生成的URL是http://localhost/myApp/foo/stuff.do。
二：
-
/表示根路径，但是jsp的根路径和servlet的根路径不一样
-
jsp的根路径：http:/ /localhost:8080 而servlet的根路径 http:localhost:8080/weapp