1、阿姆达尔定律
1.1 加速比=优化后的耗时/优化前的耗时
1.2 阿姆达尔定律 s<=1/F+(1-F)/N
其中：s为加速比，F为程序的串行化比重，n为cpu处理核数
2、调优层次（设计调优、代码调优、JVM调优、数据库调优）
2.1 设计模式
2.1.1 单列模式：常见应用spring注解，以及实现当前在线人数的统计
基本要素：构造方法私有化，提供公共的获取实例的方法
public class SingleSessionUserList { private static final SingleSessionUserList sessionUserList=new SingleSessionUserList(); //提供公共的方法接口 public static SingleSessionUserList getInstance() { return sessionUserList; } //将构造方法私有化 private SingleSessionUserList() { } }
2.1.2 代理模式
核心思想：只有在真心需要时才进行初始化，否则只返回当前对象的代理对象
基本要素：主题接口、真实主题、代理类
/** * IDbQuery * @Description 主题接口 */ public interface IDbQuery { //比较耗时的方法 public String request(); } /** * DbQuery * @Description 真实主题 */ public class DbQuery implements IDbQuery { @Override public String request() { return "比较耗时的操作结果"; } } /** * DbQueryProxy * @Description 代理类 */ public class DbQueryProxy implements IDbQuery { private DbQuery dbQuery;//真实主题 @Override public String request() { //真正需要使用DbQuery if (dbQuery==null) { dbQuery=new DbQuery(); }return dbQuery.request(); } } /** * ProxyTest * @Description 代理类的测试 */ public class ProxyTest { @Test public void testProxy() { IDbQuery dbQuery=new DbQueryProxy(); dbQuery.request(); } }
动态代理的实现
/** * JdkDbQueryHandler * @Description 使用jdk反射的反射获取动态代理 */ public class JdkDbQueryHandler implements InvocationHandler { IDbQuery dbquery; @Override public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { if (dbquery == null) { dbquery = new DbQuery(); } //调用真实主题的方法 return method.invoke(dbquery, args); } //获取动态代理对象 public static IDbQuery getJdkDbQueryProxy() { IDbQuery jdkDbQueryProxy=(IDbQuery) Proxy.newProxyInstance(ClassLoader.getSystemClassLoader(), new Class[] { IDbQuery.class }, new JdkDbQueryHandler()); return jdkDbQueryProxy; } } /** * CglibDbQueryHandler * @Description 使用cglib创建动态代理 */ public class CglibDbQueryHandler implements MethodInterceptor { private DbQuery dbQuery; @Override public Object intercept(Object proxy, Method method, Object[] args, MethodProxy methodProxy) throws Throwable { if (dbQuery==null) { dbQuery=new DbQuery(); } //调用真实主题的方法 return method.invoke(dbQuery, args); } //cglib方法获取动态代理对象 public static IDbQuery getCglibDbQueryProxy() { Enhancer enhancer=new Enhancer(); enhancer.setCallback(new CglibDbQueryHandler()); enhancer.setInterfaces(new Class[]{IDbQuery.class}); return (IDbQuery) enhancer.create(); } }
2.1.3 享元模式
核心思想：如果系统中多次使用相同的对象，每次只需要获取对象的拷贝，不需要重新创建一个新的对象
/** * IReportManager * @Description 报表管理器 */ public interface IReportManager { //生成报表 public String createReport(); } /** * FinancialReportManager * @Description 财务报表生成器实现类 */ public class FinancialReportManager implements IReportManager { @Override public String createReport() { return "财务报表"; } } /** * EmployeeReportManager * @Description 员工报表生成器 */ public class EmployeeReportManager implements IReportManager { @Override public String createReport() { return "员工报表"; } } /** * ReportManagerFactory * @Description 报表生成器工厂 */ public class ReportManagerFactory { Map<String, IReportManager> financialReportManagers=new HashMap<String, IReportManager>(); Map<String, IReportManager> employeeReportManagers=new HashMap<String, IReportManager>(); public IReportManager getFinancialReportManager(String tid) { IReportManager financialReportManager=financialReportManagers.get(tid); if (financialReportManager==null) { financialReportManager=new FinancialReportManager(); financialReportManagers.put(tid, financialReportManager); } return financialReportManager; } public IReportManager getEmployeeReportManager(String tid) { IReportManager employeeReportManager=employeeReportManagers.get(tid); if (employeeReportManager==null) { employeeReportManager=new EmployeeReportManager(); employeeReportManagers.put(tid, employeeReportManager); } return employeeReportManager; } } /** * ReportManagerFactoryTest * @Description 享元模式测试类 */ public class ReportManagerFactoryTest { @Test public void testCreateReport() { ReportManagerFactory factory=new ReportManagerFactory(); IReportManager reportManager1=factory.getEmployeeReportManager("a"); IReportManager reportManager2=factory.getEmployeeReportManager("a"); IReportManager reportManager3=factory.getEmployeeReportManager("a"); IReportManager reportManager4=factory.getFinancialReportManager("a"); IReportManager reportManager5=factory.getFinancialReportManager("a"); IReportManager reportManager6=factory.getFinancialReportManager("a"); System.out.println(reportManager1.createReport()); System.out.println(reportManager2.createReport()); System.out.println(reportManager3.createReport()); System.out.println(reportManager4.createReport()); System.out.println(reportManager5.createReport()); System.out.println(reportManager6.createReport()); } }
2.1.4 装饰模式
/** * IPacketCreator * @Description 内容处理接口 */ public interface IPacketCreator { public String handContent(); } /** * PacketCreator * @Description 内容处理具体实现 */ public class PacketCreator implements IPacketCreator { @Override public String handContent() { return "装饰模式"; } } /** * PacketDecorator * @Description 装饰器 */ public abstract class PacketDecorator implements IPacketCreator { IPacketCreator packetCreator; public PacketDecorator(IPacketCreator packetCreator) { this.packetCreator = packetCreator; } } /** * PacketHtmlDecorator * @Description 功能详细描述 */ public class PacketHtmlDecorator extends PacketDecorator { public PacketHtmlDecorator(IPacketCreator packetCreator) { super(packetCreator); } @Override public String handContent() { StringBuffer buffer=new StringBuffer("<html>"); buffer.append(packetCreator.handContent()).append("</hmtl>"); return buffer.toString(); } } /** * DecoratorTest * @Description 装饰模式测试类 */ public class DecoratorTest { @Test public void decoratorTest() { String content=new PacketHtmlDecorator(new PacketCreator()).handContent(); System.out.println(content); } }
2.2 使用缓冲区提高性能
尽量使用含有缓冲区的类进行操作，如stringBuffer,BufferInputStream等
2.3 使用缓冲技术提升性能
1.使用oscache缓存jsp局部缓冲
1.1 导入oscache的相关jar包
<dependency> <groupId>opensymphony</groupId> <artifactId>oscache</artifactId> <version>2.4.1</version> </dependency>
1.2 将oscache.properties文件放入到resource目录下
1.3 在jsp页面中导入lib文件 <%@taglib prefix="oscache" uri="http://www.opensymphony.com/oscache" %>
1.4 将需要缓存的代码使用<oscache:cache></oscache:cache>标签进行包裹
<oscache:cache key="${param.refresh }" refresh="${param.refresh }"> <div>登录时间<%=new Date() %></div> </oscache:cache>
2.使用oscache全局缓冲
2.1 在web.xml配置oscacheFilter过滤器
<filter> <filter-name>oscacheFilter</filter-name> <filter-class>com.opensymphony.oscache.web.filter.CacheFilter</filter-class> <init-param> <param-name>time</param-name> <param-value>600</param-value>p </init-param> <init-param> <param-name>scope</param-name> <param-value>application</param-value> </init-param> </filter> <filter-mapping> <filter-name>oscacheFilter</filter-name>
<!--缓存的路径--> <url-pattern>*.jsp</url-pattern> </filter-mapping>
原文：http://www.cnblogs.com/lifeone/p/6269219.html