文章目录
- 一、责任链模式定义
- 二、例子
-
- [2.1 菜鸟教程](#2.1 菜鸟教程)
-
- [2.1.1 定义一个抽象日志类](#2.1.1 定义一个抽象日志类)
- [2.1.2 定义日志类的具体实现类ConsoleLogger 、ErrorLogger 、FileLogger](#2.1.2 定义日志类的具体实现类ConsoleLogger 、ErrorLogger 、FileLogger)
- [2.1.3 将日志类串起来,并使用](#2.1.3 将日志类串起来,并使用)
- [2.2 JDK源码------Filter](#2.2 JDK源码——Filter)
- [2.3 Spring源码------HandlerInterceptor](#2.3 Spring源码——HandlerInterceptor)
- 三、其他设计模式
一、责任链模式定义
类型: 行为型模式
每个接收者都包含对另一个接收者的引用。如果一个对象不能处理该请求,那么它会把相同的请求传给下一个接收者,依此类推。
目的: 职责链上的处理者负责处理请求,客户只需要将请求发送到职责链上即可,无须关心请求的处理细节和请求的传递,所以职责链将请求的发送者和请求的处理者解耦了。
个人理解:上面菜鸟教程说职责链将发送者和请求的处理者解耦,但个人觉得职责链更多的是将多个责任解耦,使用时将所需要的责任组织成责任链。
二、例子
2.1 菜鸟教程
菜鸟教程是以一个日志类为例子。
2.1.1 定义一个抽象日志类
java
public abstract class AbstractLogger {
public static int INFO = 1;
public static int DEBUG = 2;
public static int ERROR = 3;
protected int level;
//责任链中的下一个元素
protected AbstractLogger nextLogger;
public void setNextLogger(AbstractLogger nextLogger){
this.nextLogger = nextLogger;
}
public void logMessage(int level, String message){
if(this.level <= level){
write(message);
}
if(nextLogger !=null){
nextLogger.logMessage(level, message);
}
}
abstract protected void write(String message);
}
2.1.2 定义日志类的具体实现类ConsoleLogger 、ErrorLogger 、FileLogger
java
public class ConsoleLogger extends AbstractLogger {
public ConsoleLogger(int level){
this.level = level;
}
@Override
protected void write(String message) {
System.out.println("Standard Console::Logger: " + message);
}
}
java
public class ErrorLogger extends AbstractLogger {
public ErrorLogger(int level){
this.level = level;
}
@Override
protected void write(String message) {
System.out.println("Error Console::Logger: " + message);
}
}
java
public class FileLogger extends AbstractLogger {
public FileLogger(int level){
this.level = level;
}
@Override
protected void write(String message) {
System.out.println("File::Logger: " + message);
}
}
2.1.3 将日志类串起来,并使用
java
public class ChainPatternDemo {
private static AbstractLogger getChainOfLoggers(){
AbstractLogger errorLogger = new ErrorLogger(AbstractLogger.ERROR);
AbstractLogger fileLogger = new FileLogger(AbstractLogger.DEBUG);
AbstractLogger consoleLogger = new ConsoleLogger(AbstractLogger.INFO);
errorLogger.setNextLogger(fileLogger);
fileLogger.setNextLogger(consoleLogger);
return errorLogger;
}
public static void main(String[] args) {
AbstractLogger loggerChain = getChainOfLoggers();
loggerChain.logMessage(AbstractLogger.INFO, "This is an information.");
loggerChain.logMessage(AbstractLogger.DEBUG,
"This is a debug level information.");
loggerChain.logMessage(AbstractLogger.ERROR,
"This is an error information.");
}
}
2.2 JDK源码------Filter
java
public interface Filter {
default void init(FilterConfig filterConfig) throws ServletException {
}
void doFilter(ServletRequest var1, ServletResponse var2, FilterChain var3) throws IOException, ServletException;
default void destroy() {
}
}
2.3 Spring源码------HandlerInterceptor
java
public interface HandlerInterceptor {
default boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
return true;
}
default void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, @Nullable ModelAndView modelAndView) throws Exception {
}
default void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, @Nullable Exception ex) throws Exception {
}
}
java
public class HandlerExecutionChain {
@Nullable
private HandlerInterceptor[] interceptors;
boolean applyPreHandle(HttpServletRequest request, HttpServletResponse response) throws Exception {
HandlerInterceptor[] interceptors = getInterceptors();
if (!ObjectUtils.isEmpty(interceptors)) {
for (int i = 0; i < interceptors.length; i++) {
HandlerInterceptor interceptor = interceptors[i];
if (!interceptor.preHandle(request, response, this.handler)) {
triggerAfterCompletion(request, response, null);
return false;
}
this.interceptorIndex = i;
}
}
return true;
}
void applyPostHandle(HttpServletRequest request, HttpServletResponse response, @Nullable ModelAndView mv) throws Exception {
HandlerInterceptor[] interceptors = getInterceptors();
if (!ObjectUtils.isEmpty(interceptors)) {
for (int i = interceptors.length - 1; i >= 0; i--) {
HandlerInterceptor interceptor = interceptors[i];
interceptor.postHandle(request, response, this.handler, mv);
}
}
}
void triggerAfterCompletion(HttpServletRequest request, HttpServletResponse response, @Nullable Exception ex)
throws Exception {
HandlerInterceptor[] interceptors = getInterceptors();
if (!ObjectUtils.isEmpty(interceptors)) {
for (int i = this.interceptorIndex; i >= 0; i--) {
HandlerInterceptor interceptor = interceptors[i];
try {
interceptor.afterCompletion(request, response, this.handler, ex);
}
catch (Throwable ex2) {
logger.error("HandlerInterceptor.afterCompletion threw exception", ex2);
}
}
}
}
}
三、其他设计模式
创建型模式
结构型模式
行为型模式
- 1、设计模式------访问者模式(Visitor Pattern)+ Spring相关源码
- 2、设计模式------中介者模式(Mediator Pattern)+ JDK相关源码
- 3、设计模式------策略模式(Strategy Pattern)+ Spring相关源码
- 4、设计模式------状态模式(State Pattern)
- 5、设计模式------观察者模式(Observer Pattern)+ Spring相关源码
- 6、设计模式------备忘录模式(Memento Pattern)
- 7、设计模式------模板方法模式(Template Pattern)+ Spring相关源码
- 8、设计模式------迭代器模式(Iterator Pattern)+ Spring相关源码