一文带你读懂设计模式之责任链模式 - ToB企服应用市场:ToB评测及商务社交产业平台

// 抽象处理器
public abstract class Handler {
private Handler next;
public Handler getNext() {
return next;
}
public void setNext(Handler next) {
this.next = next;
}
public abstract void handle(Object request);
}
// 具体处理器 1
public class ConcreteHandler1 extends Handler {
@Override
public void handle(Object request) {
System.out.println("concrete handler 1 execute request. request: " + request);
if (getNext() != null) {
getNext().handle(request);
}
}
}
// 具体处理器 2
public class ConcreteHandler2 extends Handler {
@Override
public void handle(Object request) {
System.out.println("concrete handler 2 execute request. request: " + request);
if (getNext() != null){
getNext().handle(request);
}
}
}
// 具体处理器 3
public class ConcreteHandler3 extends Handler {
@Override
public void handle(Object request) {
System.out.println("concrete handler 3 execute request. request: " + request);
if (getNext() != null) {
getNext().handle(request);
}
}
}
public static void main(String[] args) {
Handler concreteHandler1 = new ConcreteHandler1();
Handler concreteHandler2 = new ConcreteHandler2();
Handler concreteHandler3 = new ConcreteHandler3();
concreteHandler1.setNext(concreteHandler2);
concreteHandler2.setNext(concreteHandler3);
concreteHandler1.handle("my request.");
}

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concrete handler 1 execute request. request: my request.
concrete handler 2 execute request. request: my request.
concrete handler 3 execute request. request: my request.

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// 请假抽象处理器
public abstract class DayOffHandler {
private DayOffHandler next;
public DayOffHandler getNext() {
return next;
}
public void setNext(DayOffHandler next) {
this.next = next;
}
public abstract void handle(String request);
}
// 直属 leader 处理
public class GroupLeaderHandler extends DayOffHandler {
@Override
public void handle(String request) {
System.out.println("直属 leader 审查: " + request);
System.out.println("同意请求");
if (getNext() != null) {
getNext().handle(request);
}
}
}
// 部门 leader 处理
public class DepartmentLeaderHandler extends DayOffHandler{
@Override
public void handle(String request) {
System.out.println("部门 leader 审查: " + request);
System.out.println("同意请求");
if (getNext() != null) {
getNext().handle(request);
}
}
}
// 人事处处理
public class HRHandler extends DayOffHandler {
@Override
public void handle(String request) {
System.out.println("人事处审查: " + request);
System.out.println("同意请求，记录请假");
if (getNext() != null) {
getNext().handle(request);
}
}
}

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public static void main(String[] args) {
DayOffHandler groupLeaderHandler = new GroupLeaderHandler();
DayOffHandler departmentLeaderHandler = new DepartmentLeaderHandler();
DayOffHandler hrHandler = new HRHandler();
groupLeaderHandler.setNext(departmentLeaderHandler);
departmentLeaderHandler.setNext(hrHandler);
System.out.println("收到面试通知，需要请假");
String request = "家中有事，请假半天，望批准";
System.out.println("发起请求：");
groupLeaderHandler.handle(request);
}

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收到面试通知，需要请假
发起请求：
直属 leader 审查: 家中有事，请假半天，望批准
同意请求
部门 leader 审查: 家中有事，请假半天，望批准
同意请求
人事处审查: 家中有事，请假半天，望批准
同意请求，记录请假

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public interface Filter {
default void init(FilterConfig filterConfig) throws ServletException {
}
void doFilter(ServletRequest var1, ServletResponse var2, FilterChain var3) throws IOException, ServletException;
default void destroy() {
}
}

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public interface FilterChain {
void doFilter(ServletRequest var1, ServletResponse var2) throws IOException, ServletException;
}
public final class ApplicationFilterChain implements FilterChain {
public void doFilter(ServletRequest request, ServletResponse response) throws IOException, ServletException {
if (Globals.IS_SECURITY_ENABLED) {
final ServletRequest req = request;
final ServletResponse res = response;
try {
AccessController.doPrivileged(new PrivilegedExceptionAction<Void>() {
public Void run() throws ServletException, IOException {
ApplicationFilterChain.this.internalDoFilter(req, res);
return null;
}
});
} catch (PrivilegedActionException var7) {
Exception e = var7.getException();
if (e instanceof ServletException) {
throw (ServletException)e;
}
if (e instanceof IOException) {
throw (IOException)e;
}
if (e instanceof RuntimeException) {
throw (RuntimeException)e;
}
throw new ServletException(e.getMessage(), e);
}
} else {
this.internalDoFilter(request, response);
}
}
private void internalDoFilter(ServletRequest request, ServletResponse response) throws IOException, ServletException {
if (this.pos < this.n) {
ApplicationFilterConfig filterConfig = this.filters[this.pos++];
try {
Filter filter = filterConfig.getFilter();
if (request.isAsyncSupported() && "false".equalsIgnoreCase(filterConfig.getFilterDef().getAsyncSupported())) {
request.setAttribute("org.apache.catalina.ASYNC_SUPPORTED", Boolean.FALSE);
}
if (Globals.IS_SECURITY_ENABLED) {
Principal principal = ((HttpServletRequest)request).getUserPrincipal();
Object[] args = new Object[]{request, response, this};
SecurityUtil.doAsPrivilege("doFilter", filter, classType, args, principal);
} else {
filter.doFilter(request, response, this);
}
} catch (ServletException | RuntimeException | IOException var15) {
throw var15;
} catch (Throwable var16) {
Throwable e = ExceptionUtils.unwrapInvocationTargetException(var16);
ExceptionUtils.handleThrowable(e);
throw new ServletException(sm.getString("filterChain.filter"), e);
}
} else {
try {
if (ApplicationDispatcher.WRAP_SAME_OBJECT) {
lastServicedRequest.set(request);
lastServicedResponse.set(response);
}
if (request.isAsyncSupported() && !this.servletSupportsAsync) {
request.setAttribute("org.apache.catalina.ASYNC_SUPPORTED", Boolean.FALSE);
}
if (request instanceof HttpServletRequest && response instanceof HttpServletResponse && Globals.IS_SECURITY_ENABLED) {
Principal principal = ((HttpServletRequest)request).getUserPrincipal();
Object[] args = new Object[]{request, response};
SecurityUtil.doAsPrivilege("service", this.servlet, classTypeUsedInService, args, principal);
} else {
this.servlet.service(request, response);
}
} catch (ServletException | RuntimeException | IOException var17) {
throw var17;
} catch (Throwable var18) {
Throwable e = ExceptionUtils.unwrapInvocationTargetException(var18);
ExceptionUtils.handleThrowable(e);
throw new ServletException(sm.getString("filterChain.servlet"), e);
} finally {
if (ApplicationDispatcher.WRAP_SAME_OBJECT) {
lastServicedRequest.set((Object)null);
lastServicedResponse.set((Object)null);
}
}
}
}
}

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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 {
}
}

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public class HandlerExecutionChain {
@Nullable
private HandlerInterceptor[] interceptors;
boolean applyPreHandle(HttpServletRequest request, HttpServletResponse response) throws Exception {
HandlerInterceptor[] interceptors = this.getInterceptors();
if (!ObjectUtils.isEmpty(interceptors)) {
for(int i = 0; i < interceptors.length; this.interceptorIndex = i++) {
HandlerInterceptor interceptor = interceptors[i];
if (!interceptor.preHandle(request, response, this.handler)) {
this.triggerAfterCompletion(request, response, (Exception)null);
return false;
}
}
}
return true;
}
void applyPostHandle(HttpServletRequest request, HttpServletResponse response, @Nullable ModelAndView mv) throws Exception {
HandlerInterceptor[] interceptors = this.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 = this.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 var8) {
logger.error("HandlerInterceptor.afterCompletion threw exception", var8);
}
}
}
}
}

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