Servlet&jstl&el&过滤器&监听器&连接池--复习
Servlet的生命周期
加 jar
@WebServlet(
name="BaseControl",
urlPatterns = {
"/base1"},
initParams = {
@WebInitParam(name="page1",value="/page1.jsp"),
@WebInitParam(name="page2",value="/page2.jsp")
}
)
public class BaseControl extends HttpServlet {
private Map map=new HashMap<>();
public BaseControl(){
//1.创建
}
@Override
public void init(ServletConfig config) throws ServletException {
//初始化
map.put("page1",config.getInitParameter("page1"));
map.put("page2",config.getInitParameter("page2"));
}
@Override//3.做服务
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
super.doGet(req,resp);
}
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
System.out.println("servlet success!");
// resp.setContentType("text/html");
// resp.setCharacterEncoding("UTF-8");
// PrintWriter out=resp.getWriter();
// out.print("haoba");
// out.flush();
// out.close();
String action=req.getParameter("action");
String path=map.get(action);
RequestDispatcher dispatcher=req.getRequestDispatcher(path);
dispatcher.forward(req,resp);
}
@Override//4.销毁
public void destroy() {
super.destroy();
}
} jstl&el基础应用
加jar jstl-1.2.jar
<%@ page import="java.util.Enumeration" %>
<%@ page import="java.util.HashMap" %>
<%@ page import="java.util.Vector" %><%--
Created by IntelliJ IDEA.
User: fangjiejie
Date: 2017/11/13
Time: 19:56
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@taglib prefix="lyf" uri="http://java.sun.com/jsp/jstl/core" %>
<%@taglib prefix="ff" uri="http://java.sun.com/jsp/jstl/fmt" %>
<html>
<head>
<title>Titletitle>
head>
<body>
<lyf:out value="helloworld">lyf:out>
<lyf:set var="xiao" value="ming">lyf:set>
<br>
<lyf:out value="${xiao}">lyf:out>
<%
session.setAttribute("li","yafang");
%>
<lyf:out value="${sessionScope.li}">lyf:out>
${sessionScope.li}
<jsp:useBean id="person" class="com.LYF.Person">jsp:useBean>
<lyf:set target="${person}" property="username" value="xiaosi">lyf:set>
<lyf:if test="${person.username==ee}">
她叫小四
lyf:if>
<lyf:remove var="xiao">lyf:remove>
<lyf:out value="${xiao}"/>
<lyf:set value="20" target="${person}" property="age">lyf:set>
<lyf:choose>
<lyf:when test="${person.age<=18}">
<span>年龄小于18span>
lyf:when>
<lyf:when test="${person.age>10&&person.age<50}">
<span>年龄在18岁到50岁span>
lyf:when>
<lyf:otherwise>
<span>已经老了span>
lyf:otherwise>
lyf:choose>
<lyf:forEach var="i" begin="0" end="20" step="2">
<lyf:out value="${i}">lyf:out>
lyf:forEach>
<%
Vector vector=new Vector();
vector.add("我");
vector.add("已");
vector.add("经");
vector.add("把");
vector.add("你");
vector.add("忘");
vector.add("了");
Enumeration myEnum=vector.elements();
request.setAttribute("myEnum",myEnum);
HashMap hashMap=new HashMap();
hashMap.put("A","a");
hashMap.put("B","b");
hashMap.put("C","c");
hashMap.put("D","d");
request.setAttribute("myMap",hashMap);
%>
<lyf:forEach var="h" items="${requestScope.myMap}" varStatus="status">
<lyf:out value="${status.index}">:lyf:out><lyf:out value="${h.key}">:lyf:out>
<lyf:out value="${h.value}">lyf:out>
lyf:forEach>
<br>
<ff:formatNumber value="784523" pattern="0,000">ff:formatNumber>
<br>
<jsp:useBean id="now" class="java.util.Date">jsp:useBean>
<ff:formatDate value="${now}" var="result" pattern="yyyy-MM-dd hh:mm:ss">ff:formatDate>
${result}
<br>
<lyf:set var="ft" value="小*名*同*学">lyf:set>
<lyf:forTokens items="${ft}" delims="*" var="name" varStatus="status">
${status.count}.${name} <br>
lyf:forTokens>
body>
html>
过滤器
package com.lyf.filter;
import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import javax.servlet.annotation.WebInitParam;
import java.io.IOException;
/**
* Created by fangjiejie on 2017/11/13.
*/
@WebFilter(filterName = "encodingFilter",
urlPatterns = "/*",
initParams = @WebInitParam(name="encoder",value = "utf-8")
)
public class EncodingFilter implements Filter{
String encoding;
@Override
public void init(FilterConfig filterConfig) throws ServletException {
encoding=filterConfig.getInitParameter("encoder");
}
@Override
public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
servletRequest.setCharacterEncoding(encoding);
filterChain.doFilter(servletRequest,servletResponse);
}
@Override
public void destroy() {
}
}
监听器
package com.lyf.listener; /**
* Created by fangjiejie on 2017/11/13.
*/
import javax.servlet.ServletContextEvent;
import javax.servlet.annotation.WebListener;
import javax.servlet.http.HttpSessionBindingEvent;
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;
@WebListener()
public class OnlineListener implements HttpSessionListener {
public static int count;
// Public constructor is required by servlet spec
public OnlineListener() {
}
// -------------------------------------------------------
// ServletContextListener implementation
// -------------------------------------------------------
public void contextInitialized(ServletContextEvent sce) {
/* This method is called when the servlet context is
initialized(when the Web application is deployed).
You can initialize servlet context related data here.
*/
}
public void contextDestroyed(ServletContextEvent sce) {
/* This method is invoked when the Servlet Context
(the Web application) is undeployed or
Application Server shuts down.
*/
}
// -------------------------------------------------------
// HttpSessionListener implementation
// -------------------------------------------------------
public void sessionCreated(HttpSessionEvent se) {
++count;
/* Session is created. */
}
public void sessionDestroyed(HttpSessionEvent se) {
--count;
/* Session is destroyed. */
}
// -------------------------------------------------------
// HttpSessionAttributeListener implementation
// -------------------------------------------------------
public void attributeAdded(HttpSessionBindingEvent sbe) {
/* This method is called when an attribute
is added to a session.
*/
}
public void attributeRemoved(HttpSessionBindingEvent sbe) {
/* This method is called when an attribute
is removed from a session.
*/
}
public void attributeReplaced(HttpSessionBindingEvent sbe) {
/* This method is invoked when an attibute
is replaced in a session.
*/
}
}
连接池
作用：
连接池是将已经创建好的连接保存在池中，当有请求来时，直接使用已经创建好的连接对数据库进行访问。这样省略了创建连接和销毁连接的过程。这样性能上得到了提高。
三种连接池：
1.DBCP连接池
加jar
commons-dbcp.jar
commons-pool.jar
配置文档 dbcp.ini
#连接设置
driverClassName=com.mysql.jdbc.Driver
url=jdbc:mysql://127.0.0.1:3306/bz?useUnicode=true&characterEncoding=UTF-8
username=root
password=123321
#
initialSize=10
#最大连接数量
maxActive=50
#
maxIdle=20
#
minIdle=5
#
maxWait=60000
#JDBC驱动建立连接时附带的连接属性属性的格式必须为这样：[属性名=property;]
#注意："user" 与 "password" 两个属性会被明确地传递，因此这里不需要包含他们。
connectionProperties=useUnicode=true;characterEncoding=utf-8
#指定由连接池所创建的连接的自动提交（auto-commit）状态。
defaultAutoCommit=true
#driver default 指定由连接池所创建的连接的只读（read-only）状态。
#如果没有设置该值，则“setReadOnly”方法将不被调用。（某些驱动并不支持只读模式，如：Informix）
defaultReadOnly=
#driver default 指定由连接池所创建的连接的事务级别（TransactionIsolation）。
#可用值为下列之一：代码：
package com.lyf.db;
import org.apache.commons.dbcp2.BasicDataSourceFactory;
import javax.sql.DataSource;
import java.sql.Connection;
import java.sql.SQLException;
import java.util.Properties;
/**
* Created by fangjiejie on 2017/11/13.
*/
public class DBCP {
private static DataSource ds=null;
private static Connection conn=null;
static{
Properties pro=new Properties();
try {
pro.load(DBCP.class.getClassLoader().getResourceAsStream("dbcp.ini"));
ds= BasicDataSourceFactory.createDataSource(pro);
} catch (Exception e) {
e.printStackTrace();
}
}
public static Connection getConnection(){
try {
conn=ds.getConnection();
} catch (SQLException e) {
e.printStackTrace();
}
return conn;
}
}
2.C3P0连接池
Hibernate推荐使用它，自动清理不适用的Connection, Statement,ResultSet
加 jar
c3p0-0.9.1.2.jar
配置文档
c3p0-config.xml
<c3p0-config>
<default-config>
<property name="automaticTestTable">con_testproperty>
<property name="checkoutTimeout">30000property>
<property name="idleConnectionTestPeriod">30property>
<property name="initialPoolSize">10property>
<property name="maxIdleTime">30property>
<property name="maxPoolSize">100property>
<property name="minPoolSize">10property>
<property name="maxStatements">200property>
default-config>
<named-config name="mysql">
<property name="driverClass">com.mysql.jdbc.Driverproperty>
<property name="jdbcUrl">jdbc:mysql://localhost:3306/bz?useUnicode=true&characterEncoding=utf-8
property>
<property name="user">rootproperty>
<property name="password">123321property>
<property name="acquireIncrement">5property>
<property name="initialPoolSize">10property>
<property name="minPoolSize">5property>
<property name="maxPoolSize">30property>
named-config>
c3p0-config>package com.lyf.db;
import com.mchange.v2.c3p0.ComboPooledDataSource;
import javax.activation.DataSource;
import java.sql.Connection;
import java.sql.SQLException;
/**
* Created by fangjiejie on 2017/11/13.
*/
public class C3P0 {
private static DataSource ds=null;
private static Connection conn=null;
static {
ComboPooledDataSource cs=new ComboPooledDataSource("mysql") ;
try {
conn=cs.getConnection();
} catch (SQLException e) {
e.printStackTrace();
}
}
public static Connection getConnection(){
return conn;
}
}
3.Druid连接池
性能更好
加jar
druid-1.0.26.jar
配置文档
druid.ini
#mysql数据库
url=jdbc:mysql://127.0.0.1:3306/bz?useUnicode=true&characterEncoding=UTF-8
username=root
password=123321
#filters=stat
#最大连接数量
maxActive=20
#初始化连接数量
initialSize=10
#超时等待时间以毫秒为单位
maxWait=12000
#最小空闲连接
minIdle=5
#校验连接池中限制时间超过minEvictableIdleTimeMillis的连接对象
timeBetweenEvictionRunsMillis=6000
#连接在池中保持空闲而不被空闲连接回收器线程(如果有)回收的最小时间值，单位毫秒
#minEvictableIdleTimeMillis=
#SQL查询,用来验证从连接池取出的连接,在将连接返回给调用者之前
validationQuery=SELECT now();
#指明连接是否被空闲连接回收器(如果有)进行检验.
#如果检测失败,则连接将被从池中去除.
testWhileIdle=true
#指明是否在从池中取出连接前进行检验,如果检验失败,则从池中去除连接并尝试取出另一个.
testOnBorrow=false
#指明是否在归还到池中前进行检验
testOnReturn=false
#poolPreparedStatements=true
#maxPoolPreparedStatementPerConnectionSize=20
package com.lyf.db;
import com.alibaba.druid.pool.DruidDataSourceFactory;
import javax.sql.DataSource;
import java.sql.Connection;
import java.sql.SQLException;
import java.util.Properties;
/**
* Created by fangjiejie on 2017/4/10.
*/
public class Druid {
private static Connection conn=null;
private static DataSource ds=null;
static {
Properties pro =new Properties();
try {
pro.load(Druid.class.getClassLoader().getResourceAsStream("druid.ini"));
ds= DruidDataSourceFactory.createDataSource(pro);
} catch (Exception e) {
e.printStackTrace();
}
}
public static Connection getConnection(){
try {
conn=ds.getConnection();
} catch (SQLException e) {
e.printStackTrace();
}
return conn;
}
}
项目—对记录增删改查(Servlet&jstl&el&过滤器&监听器&连接池)
github地址：
https://github.com/stubbornA/reviewServletPro