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aop 代码_项目学生：使用AOP简化代码

發(fā)布時(shí)間：2023/12/3 编程问答 32 豆豆

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aop 代碼

這是Project Student的一部分。

許多人堅(jiān)信方法應(yīng)適合您的編輯器窗口（例如20行），而有些人認(rèn)為方法應(yīng)小于此范圍。這個(gè)想法是一種方法應(yīng)該做一件事，而只能做一件事。如果它做的還不止于此，則應(yīng)將其分解為多種方法，而舊方法的“一件事”就是協(xié)調(diào)新方法。

這并不意味著在任意數(shù)量的行之后拆分一種方法。有時(shí)方法自然會(huì)更大。仍然是一個(gè)很好的問(wèn)題。

那么，如何識(shí)別不只一件事的代碼？一個(gè)好的試金石是代碼是否在多種方法中重復(fù)。典型的例子是持久性類中的事務(wù)管理。每個(gè)持久性類都需要它，并且代碼始終看起來(lái)相同。

另一個(gè)示例是Resource類中未處理的異常處理程序。每個(gè)面向REST的方法都需要處理此問(wèn)題，并且代碼始終看起來(lái)相同。

那是理論。在實(shí)踐中，代碼可能很丑陋并且收益不大。幸運(yùn)的是，有一個(gè)解決方案：面向方面的編程（AOP）。這使我們可以在方法調(diào)用之前或之后透明地編織代碼。這通常使我們可以大大簡(jiǎn)化我們的方法。

設(shè)計(jì)決策

AspectJ –我正在通過(guò)Spring注入來(lái)使用AspectJ。

局限性

使用CRUD方法，AspectJ切入點(diǎn)表達(dá)式相對(duì)簡(jiǎn)單。當(dāng)添加了更復(fù)雜的功能時(shí)，情況可能并非如此。

資源方法中未處理的異常

我們首先關(guān)心的是資源方法中未處理的異常。不管怎樣，Jersey都會(huì)返回SERVER INTERNAL ERROR（服務(wù)器內(nèi)部錯(cuò)誤）（500）消息，但它可能包含堆棧跟蹤信息和我們不希望攻擊者知道的其他內(nèi)容。如果我們自己發(fā)送它，我們可以控制它包含的內(nèi)容。我們可以在所有方法中添加一個(gè)“ catch”塊，但可以將其復(fù)制到AOP方法中。這將使我們所有的Resource方法更加苗條和易于閱讀。

此類還檢查“找不到對(duì)象”異常。在單個(gè)Resource類中將很容易處理，但會(huì)使代碼混亂。將異常處理程序放在此處可使我們的方法專注于快樂(lè)路徑并保證響應(yīng)的一致性。

該類有兩個(gè)優(yōu)化。首先，它顯式檢查UnitTestException并在這種情況下跳過(guò)詳細(xì)的日志記錄。我最大的煩惱之一就是當(dāng)一切都按預(yù)期方式運(yùn)行時(shí)，使用堆棧跟蹤信息淹沒(méi)日志的測(cè)試。這使得不可能針對(duì)明顯的問(wèn)題瀏覽日志。單個(gè)更改可以使問(wèn)題更容易發(fā)現(xiàn)。

其次，它使用與目標(biāo)類（例如CourseResource）關(guān)聯(lián)的記錄器，而不是與AOP類關(guān)聯(lián)的記錄器。除了更清晰之外，這還使我們可以有選擇地更改單個(gè)Resource（而不是全部）的日志記錄級(jí)別。

另一個(gè)技巧是在處理程序中調(diào)用ExceptionService 。該服務(wù)可以對(duì)異常做一些有用的事情，例如，它可以創(chuàng)建或更新Jira票證。這還沒(méi)有實(shí)現(xiàn)，所以我只是發(fā)表評(píng)論以說(shuō)明它的去向。

@Aspect @Component public class UnexpectedResourceExceptionHandler {@Around("target(com.invariantproperties.sandbox.student.webservice.server.rest.AbstractResource)")public Object checkForUnhandledException(ProceedingJoinPoint pjp) throws Throwable {Object results = null;Logger log = Logger.getLogger(pjp.getSignature().getClass());try {results = pjp.proceed(pjp.getArgs());} catch (ObjectNotFoundException e) {// this is safe to log since we know that we've passed filtering.String args = Arrays.toString(pjp.getArgs());results = Response.status(Status.NOT_FOUND).entity("object not found: " + args).build();if (log.isDebugEnabled()) {log.debug("object not found: " + args);}} catch (Exception e) {// find the method we called. We can't cache this since the method// may be overloadedMethod method = findMethod(pjp); if ((method != null) && Response.class.isAssignableFrom(method.getReturnType())) {// if the method returns a response we can return a 500 message.if (!(e instanceof UnitTestException)) {if (log.isInfoEnabled()) {log.info(String.format("%s(): unhandled exception: %s", pjp.getSignature().getName(),e.getMessage()), e);}} else if (log.isTraceEnabled()) {log.info("unit test exception: " + e.getMessage());}results = Response.status(Status.INTERNAL_SERVER_ERROR).build();} else {// DO NOT LOG THE EXCEPTION. That just clutters the log - let// the final handler log it.throw e;}}return results;}/*** Find method called via reflection.*/Method findMethod(ProceedingJoinPoint pjp) {Class[] argtypes = new Class[pjp.getArgs().length];for (int i = 0; i < argtypes.length; i++) {argtypes[i] = pjp.getArgs()[i].getClass();}Method method = null;try {// @SuppressWarnings("unchecked")method = pjp.getSignature().getDeclaringType().getMethod(pjp.getSignature().getName(), argtypes);} catch (Exception e) {Logger.getLogger(UnexpectedResourceExceptionHandler.class).info(String.format("could not find method for %s.%s", pjp.getSignature().getDeclaringType().getName(),pjp.getSignature().getName()));}return method;} }

REST發(fā)布值檢查

我們的Resource方法也有很多樣板代碼來(lái)檢查REST參數(shù)。它們是否為非空，電子郵件地址的格式是否正確，等等。同樣，很容易將許多代碼移入AOP方法并簡(jiǎn)化Resource方法。

我們首先定義一個(gè)接口，該接口指示可以驗(yàn)證REST傳輸對(duì)象。第一個(gè)版本使我們可以簡(jiǎn)單地接受或拒絕，改進(jìn)的版本將使我們有辦法告訴客戶具體問(wèn)題是什么。

public interface Validatable {boolean validate(); }

現(xiàn)在，我們擴(kuò)展了先前的REST傳輸對(duì)象，以添加一種驗(yàn)證方法。

兩個(gè)筆記。首先，名稱和電子郵件地址接受Unicode字母，而不僅僅是標(biāo)準(zhǔn)ASCII字母。隨著我們的世界國(guó)際化，這一點(diǎn)很重要。

其次，我添加了一個(gè)toString（）方法，但是由于它使用了未經(jīng)處理的值，因此它是不安全的。我將在稍后處理消毒。

@XmlRootElement public class NameAndEmailAddressRTO implements Validatable {// names must be alphabetic, an apostrophe, a dash or a space. (Anne-Marie,// O'Brien). This pattern should accept non-Latin characters.// digits and colon are added to aid testing. Unlikely but possible in real// names.private static final Pattern NAME_PATTERN = Pattern.compile("^[\\p{L}\\p{Digit}' :-]+$");// email address must be well-formed. This pattern should accept non-Latin// characters.private static final Pattern EMAIL_PATTERN = Pattern.compile("^[^@]+@([\\p{L}\\p{Digit}-]+\\.)?[\\p{L}]+");private String name;private String emailAddress;private String testUuid;public String getName() {return name;}public void setName(String name) {this.name = name;}public String getEmailAddress() {return emailAddress;}public void setEmailAddress(String emailAddress) {this.emailAddress = emailAddress;}public String getTestUuid() {return testUuid;}public void setTestUuid(String testUuid) {this.testUuid = testUuid;}/*** Validate values.*/@Overridepublic boolean validate() {if ((name == null) || !NAME_PATTERN.matcher(name).matches()) {return false;}if ((emailAddress == null) || !EMAIL_PATTERN.matcher(emailAddress).matches()) {return false;}if ((testUuid != null) && !StudentUtil.isPossibleUuid(testUuid)) {return false;}return true;}@Overridepublic String toString() {// FIXME: this is unsafe!return String.format("NameAndEmailAddress('%s', '%s', %s)", name, emailAddress, testUuid);} }

我們對(duì)其他REST傳輸對(duì)象進(jìn)行了類似的更改。

現(xiàn)在，我們可以編寫AOP方法來(lái)檢查CRUD操作的參數(shù)。和以前一樣，使用與資源關(guān)聯(lián)的記錄器而不是AOP類來(lái)寫入日志。

這些方法還記錄Resource方法的條目。同樣，它是樣板，在此進(jìn)行簡(jiǎn)化了Resource方法。記錄該方法的退出和運(yùn)行時(shí)間也很簡(jiǎn)單，但是在這種情況下，我們應(yīng)該使用一個(gè)股票記錄器AOP類。

@Aspect @Component public class CheckPostValues {/*** Check post values on create method.* * @param pjp* @return* @throws Throwable*/@Around("target(com.invariantproperties.sandbox.student.webservice.server.rest.AbstractResource) && args(validatable,..)")public Object checkParametersCreate(ProceedingJoinPoint pjp, Validatable rto) throws Throwable {final Logger log = Logger.getLogger(pjp.getSignature().getDeclaringType());final String name = pjp.getSignature().getName();Object results = null;if (rto.validate()) {// this should be safe since parameters have been validated.if (log.isDebugEnabled()) {log.debug(String.format("%s(%s): entry", name, Arrays.toString(pjp.getArgs())));}results = pjp.proceed(pjp.getArgs());} else {// FIXME: this is unsafeif (log.isInfoEnabled()) {log.info(String.format("%s(%s): bad arguments", name, Arrays.toString(pjp.getArgs())));}// TODO: tell caller what the problems wereresults = Response.status(Status.BAD_REQUEST).build();}return results;}/*** Check post values on update method.* * @param pjp* @return* @throws Throwable*/@Around("target(com.invariantproperties.sandbox.student.webservice.server.rest.AbstractResource) && args(uuid,validatable,..)")public Object checkParametersUpdate(ProceedingJoinPoint pjp, String uuid, Validatable rto) throws Throwable {final Logger log = Logger.getLogger(pjp.getSignature().getDeclaringType());final String name = pjp.getSignature().getName();Object results = null;if (!StudentUtil.isPossibleUuid(uuid)) {// this is a possible attack.if (log.isInfoEnabled()) {log.info(String.format("%s(): uuid", name));}results = Response.status(Status.BAD_REQUEST).build();} else if (rto.validate()) {// this should be safe since parameters have been validated.if (log.isDebugEnabled()) {log.debug(String.format("%s(%s): entry", name, Arrays.toString(pjp.getArgs())));}results = pjp.proceed(pjp.getArgs());} else {// FIXME: this is unsafeif (log.isInfoEnabled()) {log.info(String.format("%s(%s): bad arguments", name, Arrays.toString(pjp.getArgs())));}// TODO: tell caller what the problems wereresults = Response.status(Status.BAD_REQUEST).build();}return results;}/*** Check post values on delete method. This is actually a no-op but it* allows us to log method entry.* * @param pjp* @return* @throws Throwable*/@Around("target(com.invariantproperties.sandbox.student.webservice.server.rest.AbstractResource) && args(uuid,version) && execution(* *.delete*(..))")public Object checkParametersDelete(ProceedingJoinPoint pjp, String uuid, Integer version) throws Throwable {final Logger log = Logger.getLogger(pjp.getSignature().getDeclaringType());final String name = pjp.getSignature().getName();Object results = null;if (!StudentUtil.isPossibleUuid(uuid)) {// this is a possible attack.if (log.isInfoEnabled()) {log.info(String.format("%s(): uuid", name));}results = Response.status(Status.BAD_REQUEST).build();} else {// this should be safe since parameters have been validated.if (log.isDebugEnabled()) {log.debug(String.format("%s(%s): entry", name, Arrays.toString(pjp.getArgs())));}results = pjp.proceed(pjp.getArgs());}return results;}/*** Check post values on find methods. This is actually a no-op but it allows* us to log method entry.* * @param pjp* @return* @throws Throwable*/@Around("target(com.invariantproperties.sandbox.student.webservice.server.rest.AbstractResource) && execution(* *.find*(..))")public Object checkParametersFind(ProceedingJoinPoint pjp) throws Throwable {final Logger log = Logger.getLogger(pjp.getSignature().getDeclaringType());if (log.isDebugEnabled()) {log.debug(String.format("%s(%s): entry", pjp.getSignature().getName(), Arrays.toString(pjp.getArgs())));}final Object results = pjp.proceed(pjp.getArgs());return results;} }

更新了Spring配置

我們必須告訴Spring搜索AOP類。這是對(duì)我們的配置文件的單行更改。

更新資源

現(xiàn)在，我們可以簡(jiǎn)化資源類。僅有幾種方法可以簡(jiǎn)化為幸福道路。

@Service @Path("/course") public class CourseResource extends AbstractResource {private static final Logger LOG = Logger.getLogger(CourseResource.class);private static final Course[] EMPTY_COURSE_ARRAY = new Course[0];@Resourceprivate CourseFinderService finder;@Resourceprivate CourseManagerService manager;@Resourceprivate TestRunService testRunService;/*** Default constructor.*/public CourseResource() {}/*** Set values used in unit tests. (Required due to AOP)* * @param finder* @param manager* @param testService*/void setServices(CourseFinderService finder, CourseManagerService manager, TestRunService testRunService) {this.finder = finder;this.manager = manager;this.testRunService = testRunService;}/*** Get all Courses.* * @return*/@GET@Produces({ MediaType.APPLICATION_JSON, MediaType.TEXT_XML })public Response findAllCourses() {final List courses = finder.findAllCourses();final List results = new ArrayList(courses.size());for (Course course : courses) {results.add(scrubCourse(course));}final Response response = Response.ok(results.toArray(EMPTY_COURSE_ARRAY)).build();return response;}/*** Create a Course.* * FIXME: what about uniqueness violations?* * @param req* @return*/@POST@Consumes({ MediaType.APPLICATION_JSON, MediaType.TEXT_XML })@Produces({ MediaType.APPLICATION_JSON, MediaType.TEXT_XML })public Response createCourse(CourseInfo req) {final String code = req.getCode();final String name = req.getName();Response response = null;Course course = null;if (req.getTestUuid() != null) {TestRun testRun = testRunService.findTestRunByUuid(req.getTestUuid());if (testRun != null) {course = manager.createCourseForTesting(code, name, req.getSummary(), req.getDescription(),req.getCreditHours(), testRun);} else {response = Response.status(Status.BAD_REQUEST).entity("unknown test UUID").build();}} else {course = manager.createCourse(code, name, req.getSummary(), req.getDescription(), req.getCreditHours());}if (course == null) {response = Response.status(Status.INTERNAL_SERVER_ERROR).build();} else {response = Response.created(URI.create(course.getUuid())).entity(scrubCourse(course)).build();}return response;}/*** Get a specific Course.* * @param uuid* @return*/@Path("/{courseId}")@GET@Produces({ MediaType.APPLICATION_JSON, MediaType.TEXT_XML })public Response getCourse(@PathParam("courseId") String id) {// 'object not found' handled by AOPCourse course = finder.findCourseByUuid(id);final Response response = Response.ok(scrubCourse(course)).build();return response;}/*** Update a Course.* * FIXME: what about uniqueness violations?* * @param id* @param req* @return*/@Path("/{courseId}")@POST@Consumes({ MediaType.APPLICATION_JSON, MediaType.TEXT_XML })@Produces({ MediaType.APPLICATION_JSON, MediaType.TEXT_XML })public Response updateCourse(@PathParam("courseId") String id, CourseInfo req) {final String name = req.getName();// 'object not found' handled by AOPfinal Course course = finder.findCourseByUuid(id);final Course updatedCourse = manager.updateCourse(course, name, req.getSummary(), req.getDescription(),req.getCreditHours());final Response response = Response.ok(scrubCourse(updatedCourse)).build();return response;}/*** Delete a Course.* * @param id* @return*/@Path("/{courseId}")@DELETEpublic Response deleteCourse(@PathParam("courseId") String id, @PathParam("version") Integer version) {// we don't use AOP handler since it's okay for there to be no matchtry {manager.deleteCourse(id, version);} catch (ObjectNotFoundException exception) {LOG.debug("course not found: " + id);}final Response response = Response.noContent().build();return response;} }

單元測(cè)試

單元測(cè)試需要對(duì)每個(gè)測(cè)試進(jìn)行更改，因?yàn)槲覀儾荒芎?jiǎn)單地實(shí)例化被測(cè)試的對(duì)象–我們必須使用Spring，以便正確編織AOP類。幸運(yùn)的是，這實(shí)際上是唯一的更改–我們檢索資源并通過(guò)package-private方法而不是package-private構(gòu)造函數(shù)設(shè)置服務(wù)。

我們還需要為服務(wù)bean創(chuàng)建Spring值。配置器類負(fù)責(zé)此工作。

@Configuration @ComponentScan(basePackages = { "com.invariantproperties.sandbox.student.webservice.server.rest" }) @ImportResource({ "classpath:applicationContext-rest.xml" }) // @PropertySource("classpath:application.properties") public class TestRestApplicationContext1 {@Beanpublic CourseFinderService courseFinderService() {return null;}@Beanpublic CourseManagerService courseManagerService() {return null;}....

整合測(cè)試

集成測(cè)試不需要任何更改。

源代碼

源代碼位于https://github.com/beargiles/project-student [github]和http://beargiles.github.io/project-student/ [github頁(yè)面]。

參考：項(xiàng)目學(xué)生：來(lái)自Invariant Properties博客的JCG合作伙伴 Bear Giles 使用AOP簡(jiǎn)化代碼。

翻譯自: https://www.javacodegeeks.com/2014/01/project-student-simplifying-code-with-aop.html