Project Student：维护Webapp（可编辑）

这是Project Student的一部分。其他帖子包括带有Jersey的 Web服务客户端，带有Jersey的 Web服务服务器，业务层，具有Spring数据的持久性，分片集成测试数据， Webservice集成， JPA标准查询和维护Webapp（只读）。

上一次我们创建了一个简单的Web应用程序，使我们可以快速浏览数据库。它的功能非常有限-主要目的是将一个系统组合在一起，以行使从Web浏览器到数据库的整个堆栈。这次我们添加了实际的CRUD支持。

这篇文章是从Jumpstart网站大量借用的，但有很大的不同。有很多代码，但是很容易重用。

局限性

用户身份验证 –尚未进行身份验证的工作。
加密 –尚未对通信进行加密。
分页 –尚未做出任何努力来支持分页。 Tapestry 5组件将显示分页外观，但始终包含相同的第一页数据。
错误消息 –将显示错误消息，但服务器端错误目前尚无信息。
跨站点脚本（XSS） –尚未做出任何努力来防止XSS攻击。
国际化 –尚未做出任何努力来支持国际化。

目标

我们需要标准的CRUD页面。

首先，我们需要能够创建一门新课程。当我们没有任何数据时，我们的课程列表应包含一个链接作为默认消息。（第一个“创建...”是一个单独的元素。）

现在，创建页面具有多个字段。代码唯一地标识一门课程，例如CSCI 101，其名称，摘要和描述应不言自明。

创建成功后，我们将进入评论页面。

如果需要进行更改，然后返回更新页面。

任何时候我们都可以返回列表页面。

在删除记录之前，系统会提示我们进行确认。

最后，我们可以显示服务器端错误，例如对于唯一字段中的重复值，即使此刻消息非常无用。

我们也有客户端错误检查，尽管我在这里没有显示。

Index.tml

我们从索引页面开始。这与我们在上一篇文章中看到的相似。

Tapestry 5具有三种主要类型的链接。 页面链接被映射到标准HTML链接。一个ActionLink的是直接由相应的类，例如，Index.java为Index.tml模板处理。最后，一个事件链接将一个事件注入到挂毯引擎内的正常事件流中。我所有的链接都转到一个密切相关的页面，所以我使用一个动作链接。

<html t:type="layout" title="Course List"t:sidebarTitle="Framework Version"xmlns:t="http://tapestry.apache.org/schema/tapestry_5_3.xsd"xmlns:p="tapestry:parameter"><t:zone t:id="zone">   <p>"Course" page</p><t:actionlink t:id="create">Create...</t:actionlink><br/><t:grid source="courses" row="course" include="code, name,creationdate" add="edit,delete"><p:codecell><t:actionlink t:id="view" context="course.uuid">${course.code}</t:actionlink></p:codecell><p:editcell><t:actionlink t:id="update" context="course.uuid">Edit</t:actionlink></p:editcell><p:deletecell><t:actionlink t:id="delete" context="course.uuid" t:mixins="Confirm" t:message="Delete ${course.name}?">Delete</t:actionlink></p:deletecell><p:empty><p>There are no courses to display; you can <t:actionlink t:id="create1">create</t:actionlink> one.</p></p:empty></t:grid></t:zone><p:sidebar><p>[<t:pagelink page="Index">Index</t:pagelink>]<br/>[<t:pagelink page="Course/Index">Courses</t:pagelink>]</p></p:sidebar></html>

确认混入

Index.tml模板在删除操作链接上包含一个“ mixin”。它使用javascript和java的混合显示弹出消息，要求用户确认他要删除课程。

该代码直接来自Jumpstart和Tapestry网站。

// from http://jumpstart.doublenegative.com.au/
Confirm = Class.create({initialize: function(elementId, message) {this.message = message;Event.observe($(elementId), 'click', this.doConfirm.bindAsEventListener(this));},doConfirm: function(e) {// Pop up a javascript Confirm Box (see http://www.w3schools.com/js/js_popup.asp)if (!confirm(this.message)) {e.stop();}}
})// Extend the Tapestry.Initializer with a static method that instantiates a Confirm.Tapestry.Initializer.confirm = function(spec) {new Confirm(spec.elementId, spec.message);
}

相应的Java代码是

// from http://jumpstart.doublenegative.com.au/
@Import(library = "confirm.js")
public class Confirm {@Parameter(name = "message", value = "Are you sure?", defaultPrefix = BindingConstants.LITERAL)private String message;@Injectprivate JavaScriptSupport javaScriptSupport;@InjectContainerprivate ClientElement clientElement;@AfterRenderpublic void afterRender() {// Tell the Tapestry.Initializer to do the initializing of a Confirm,// which it will do when the DOM has been// fully loaded.JSONObject spec = new JSONObject();spec.put("elementId", clientElement.getClientId());spec.put("message", message);javaScriptSupport.addInitializerCall("confirm", spec);}
}

Index.java

支持索引模板的Java很简单，因为我们只需要定义一个数据源并提供一些动作处理程序即可。

package com.invariantproperties.sandbox.student.maintenance.web.pages.course;public class Index {@Property@Inject@Symbol(SymbolConstants.TAPESTRY_VERSION)private String tapestryVersion;@InjectComponentprivate Zone zone;@Injectprivate CourseFinderService courseFinderService;@Injectprivate CourseManagerService courseManagerService;@Propertyprivate Course course;// our sibling page@InjectPageprivate com.invariantproperties.sandbox.student.maintenance.web.pages.course.Editor editorPage;/*** Get the datasource containing our data.* * @return*/public GridDataSource getCourses() {return new CoursePagedDataSource(courseFinderService);}/*** Handle a delete request. This could fail, e.g., if the course has already* been deleted.* * @param courseUuid*/void onActionFromDelete(String courseUuid) {courseManagerService.deleteCourse(courseUuid, 0);}/*** Bring up editor page in create mode.* * @param courseUuid* @return*/Object onActionFromCreate() {editorPage.setup(Mode.CREATE, null);return editorPage;}/*** Bring up editor page in create mode.* * @param courseUuid* @return*/Object onActionFromCreate1() {return onActionFromCreate();}/*** Bring up editor page in review mode.* * @param courseUuid* @return*/Object onActionFromView(String courseUuid) {editorPage.setup(Mode.REVIEW, courseUuid);return editorPage;}/*** Bring up editor page in update mode.* * @param courseUuid* @return*/Object onActionFromUpdate(String courseUuid) {editorPage.setup(Mode.UPDATE, courseUuid);return editorPage;}
}

Editor.tml

CRUD页面可以是三个单独的页面（用于创建，查看和更新），也可以是一个页面。我遵循的是Jumpstart网站所使用的模式–一个页面。老实说-我不确定他为什么做出这个决定-也许是因为页面紧密相关并且他使用事件处理？无论如何，我将分别讨论这些元素。

创建模板

“创建”模板是一种简单的形式。您可以看到HTML <input>元素得到了增强，它们具有一些特定于挂毯的属性，以及一些其他标记，例如<t：errors />和<t：submit>。

CustomForm和CustomError是标准Tapestry Form和Error类的本地扩展。它们目前为空，但允许我们轻松添加本地扩展。

<html t:type="layout" title="Course Editor"t:sidebarTitle="Framework Version"xmlns:t="http://tapestry.apache.org/schema/tapestry_5_3.xsd" xmlns:p="tapestry:parameter"><t:zone t:id="zone">   <t:if test="modeCreate"><h1>Create</h1><form t:type="form" t:id="createForm" ><t:errors/><table><tr><th><t:label for="code"/>:</th><td><input t:type="TextField" t:id="code" value="course.code" t:validate="required, maxlength=12" size="12"/></td><td>(required)</td></tr><tr class="err"><th></th><td colspan="2"><t:CustomError for="code"/></td></tr><tr><th><t:label for="name"/>:</th><td><input t:type="TextField" t:id="name" value="course.name" t:validate="required, maxlength=80" size="45"/></td><td>(required)</td></tr><tr class="err"><th></th><td colspan="2"><t:CustomError for="name"/></td></tr><tr><th><t:label for="summary"/>:</th><td><input cols="50" rows="4" t:type="TextArea" t:id="summary" value="course.summary" t:validate="maxlength=400"/></td></tr><tr class="err"><th></th><td colspan="2"><t:CustomError for="summary"/></td></tr><tr><th><t:label for="description"/>:</th><td><input cols="50" rows="12" t:type="TextArea" t:id="description" value="course.description" t:validate="maxlength=2000"/></td></tr><tr class="err"><th></th><td colspan="2"><t:CustomError for="description"/></td></tr></table><div class="buttons"><t:submit t:event="cancelCreate" t:context="course.uuid" value="Cancel"/><input type="submit" value="Save"/></div></form></t:if>...
</html>

创建java

相应的java类很简单。我们必须定义一些自定义事件。
ActivationRequestParameter值是从URL查询字符串中提取的。
课程字段包含创建新对象时要使用的值。
courseForm字段在模板上包含相应的<form>。
indexPage包含对索引页的引用。

有四个名为onEventFromCreateForm的事件处理程序，其中event
可以准备，验证，成功或失败。每个事件处理程序都有非常特定的角色。

还有一个附加的事件处理程序onCancelCreate（） 。您可以在模板的<t：submit>标记中看到该事件的名称。

/*** This component will trigger the following events on its container (which in* this example is the page):* {@link Editor.web.components.examples.component.crud.Editor#CANCEL_CREATE} ,* {@link Editor.web.components.examples.component.crud.Editor#SUCCESSFUL_CREATE}* (Long courseUuid),* {@link Editor.web.components.examples.component.crud.Editor#FAILED_CREATE} ,*/
// @Events is applied to a component solely to document what events it may
// trigger. It is not checked at runtime.
@Events({ Editor.CANCEL_CREATE, Editor.SUCCESSFUL_CREATE, Editor.FAILED_CREATE })
public class Editor {public static final String CANCEL_CREATE = "cancelCreate";public static final String SUCCESSFUL_CREATE = "successfulCreate";public static final String FAILED_CREATE = "failedCreate";public enum Mode {CREATE, REVIEW, UPDATE;}// Parameters@ActivationRequestParameter@Propertyprivate Mode mode;@ActivationRequestParameter@Propertyprivate String courseUuid;// Screen fields@Propertyprivate Course course;// Work fields// This carries version through the redirect that follows a server-side// validation failure.@Persist(PersistenceConstants.FLASH)private Integer versionFlash;// Generally useful bits and pieces@Injectprivate CourseFinderService courseFinderService;@Injectprivate CourseManagerService courseManagerService;@Componentprivate CustomForm createForm;@Injectprivate ComponentResources componentResources;@InjectPageprivate com.invariantproperties.sandbox.student.maintenance.web.pages.course.Index indexPage;// The codepublic void setup(Mode mode, String courseUuid) {this.mode = mode;this.courseUuid = courseUuid;}// setupRender() is called by Tapestry right before it starts rendering the// component.void setupRender() {if (mode == Mode.REVIEW) {if (courseUuid == null) {course = null;// Handle null course in the template.} else {if (course == null) {try {course = courseFinderService.findCourseByUuid(courseUuid);} catch (ObjectNotFoundException e) {// Handle null course in the template.}}}}}// /// CREATE// /// Handle event "cancelCreate"Object onCancelCreate() {return indexPage;}// Component "createForm" bubbles up the PREPARE event when it is rendered// or submittedvoid onPrepareFromCreateForm() throws Exception {// Instantiate a Course for the form data to overlay.course = new Course();}// Component "createForm" bubbles up the VALIDATE event when it is submittedvoid onValidateFromCreateForm() {if (createForm.getHasErrors()) {// We get here only if a server-side validator detected an error.return;}try {course = courseManagerService.createCourse(course.getCode(), course.getName(), course.getSummary(),course.getDescription(), 1);} catch (RestClientFailureException e) {createForm.recordError("Internal error on server.");createForm.recordError(e.getMessage());} catch (Exception e) {createForm.recordError(ExceptionUtil.getRootCauseMessage(e));}}// Component "createForm" bubbles up SUCCESS or FAILURE when it is// submitted, depending on whether VALIDATE// records an errorboolean onSuccessFromCreateForm() {componentResources.triggerEvent(SUCCESSFUL_CREATE, new Object[] { course.getUuid() }, null);// We don't want "success" to bubble up, so we return true to say we've// handled it.mode = Mode.REVIEW;courseUuid = course.getUuid();return true;}boolean onFailureFromCreateForm() {// Rather than letting "failure" bubble up which doesn't say what you// were trying to do, we trigger new event// "failedCreate". It will bubble up because we don't have a handler// method for it.componentResources.triggerEvent(FAILED_CREATE, null, null);// We don't want "failure" to bubble up, so we return true to say we've// handled it.return true;}....
}

评论模板

“审阅”模板是一个简单的表。它以表格形式包装，但仅用于页面底部的导航按钮。

<t:if test="modeReview"><h1>Review</h1><strong>Warning: no attempt is made to block XSS</strong><form t:type="form" t:id="reviewForm"><t:errors/><t:if test="course"><div t:type="if" t:test="deleteMessage" class="error">${deleteMessage}</div><table><tr><th>Uuid:</th><td>${course.uuid}</td></tr><tr><th>Code:</th><td>${course.code}</td></tr><tr><th>Name:</th><td>${course.name}</td></tr><tr><th>Summary:</th><td>${course.summary}</td></tr><tr><th>Description:</th><td>${course.description}</td></tr></table><div class="buttons"><t:submit t:event="toIndex" t:context="course.uuid" value="List"/><t:submit t:event="toUpdate" t:context="course.uuid" value="Update"/><t:submit t:event="delete" t:context="course.uuid" t:mixins="Confirm" t:message="Delete ${course.name}?" value="Delete"/></div></t:if><t:if negate="true" test="course">Course ${courseUuid} does not exist.<br/><br/></t:if></form></t:if>

回顾java

审阅表单所需的Java很简单-我们只需要加载数据即可。我本来希望setupRender（）足够，但实际上我需要onPrepareFromReviewForm（）方法。

public class Editor {public enum Mode {CREATE, REVIEW, UPDATE;}// Parameters@ActivationRequestParameter@Propertyprivate Mode mode;@ActivationRequestParameter@Propertyprivate String courseUuid;// Screen fields@Propertyprivate Course course;// Generally useful bits and pieces@Injectprivate CourseFinderService courseFinderService;@Componentprivate CustomForm reviewForm;@Injectprivate ComponentResources componentResources;@InjectPageprivate com.invariantproperties.sandbox.student.maintenance.web.pages.course.Index indexPage;// The codepublic void setup(Mode mode, String courseUuid) {this.mode = mode;this.courseUuid = courseUuid;}// setupRender() is called by Tapestry right before it starts rendering the// component.void setupRender() {if (mode == Mode.REVIEW) {if (courseUuid == null) {course = null;// Handle null course in the template.} else {if (course == null) {try {course = courseFinderService.findCourseByUuid(courseUuid);} catch (ObjectNotFoundException e) {// Handle null course in the template.}}}}}// /// REVIEW// /void onPrepareFromReviewForm() {try {course = courseFinderService.findCourseByUuid(courseUuid);} catch (ObjectNotFoundException e) {// Handle null course in the template.}}// /// PAGE NAVIGATION// /// Handle event "toUpdate"boolean onToUpdate(String courseUuid) {mode = Mode.UPDATE;return false;}// Handle event "toIndex"Object onToIndex() {return indexPage;}....
}

UPDATE模板

最后，“更新”模板看起来类似于“创建”模板。

<t:if test="modeUpdate"><h1>Update</h1><strong>Warning: no attempt is made to block XSS</strong><form t:type="form" t:id="updateForm"><t:errors/><t:if test="course"><!-- If optimistic locking is not needed then comment out this next line. It works because Hidden fields are part of the submit. --><!-- <t:hidden value="course.version"/> --><table><tr><th><t:label for="updCode"/>:</th><td><input t:type="TextField" t:id="updCode" value="course.code" t:disabled="true" size="12"/></td><td>(read-only)</td></tr><tr class="err"><th></th><td colspan="2"><t:CustomError for="updName"/></td></tr><tr><th><t:label for="updName"/>:</th><td><input t:type="TextField" t:id="updName" value="course.name" t:validate="required, maxlength=80" size="45"/></td><td>(required)</td></tr><tr class="err"><th></th><td colspan="2"><t:CustomError for="updSummary"/></td></tr><tr><th><t:label for="updSummary"/>:</th><td><input cols="50" rows="4" t:type="TextArea" t:id="updSummary" value="course.summary" t:validate="maxlength=400"/></td></tr><tr class="err"><th></th><td colspan="2"><t:CustomError for="updSummary"/></td></tr><tr><th><t:label for="updDescription"/>:</th><td><input cols="50" rows="12" t:type="TextArea" t:id="updDescription" value="course.description" t:validate="maxlength=50"/></td></tr><tr class="err"><th></th><td colspan="2"><t:CustomError for="updDescription"/></td></tr></table><div class="buttons"><t:submit t:event="toIndex" t:context="course.uuid" value="List"/><t:submit t:event="cancelUpdate" t:context="course.uuid" value="Cancel"/><input t:type="submit" value="Save"/></div></t:if><t:if negate="true" test="course">Course ${courseUuid} does not exist.<br/><br/></t:if></form>    </t:if>

更新java

同样，“更新” Java代码看起来很像“创建” Java代码。最大的区别在于，我们必须能够处理在尝试更新数据库之前已删除课程的比赛条件。

@Events({ Editor.TO_UPDATE, Editor.CANCEL_UPDATE,Editor.SUCCESSFUL_UPDATE, Editor.FAILED_UPDATE })
public class Editor {public static final String TO_UPDATE = "toUpdate";public static final String CANCEL_UPDATE = "cancelUpdate";public static final String SUCCESSFUL_UPDATE = "successfulUpdate";public static final String FAILED_UPDATE = "failedUpdate";public enum Mode {CREATE, REVIEW, UPDATE;}// Parameters@ActivationRequestParameter@Propertyprivate Mode mode;@ActivationRequestParameter@Propertyprivate String courseUuid;// Screen fields@Propertyprivate Course course;@Property@Persist(PersistenceConstants.FLASH)private String deleteMessage;// Work fields// This carries version through the redirect that follows a server-side// validation failure.@Persist(PersistenceConstants.FLASH)private Integer versionFlash;// Generally useful bits and pieces@Injectprivate CourseFinderService courseFinderService;@Injectprivate CourseManagerService courseManagerService;@Componentprivate CustomForm updateForm;@Injectprivate ComponentResources componentResources;@InjectPageprivate com.invariantproperties.sandbox.student.maintenance.web.pages.course.Index indexPage;// The codepublic void setup(Mode mode, String courseUuid) {this.mode = mode;this.courseUuid = courseUuid;}// setupRender() is called by Tapestry right before it starts rendering the// component.void setupRender() {if (mode == Mode.REVIEW) {if (courseUuid == null) {course = null;// Handle null course in the template.} else {if (course == null) {try {course = courseFinderService.findCourseByUuid(courseUuid);} catch (ObjectNotFoundException e) {// Handle null course in the template.}}}}}// /// UPDATE// /// Handle event "cancelUpdate"Object onCancelUpdate(String courseUuid) {return indexPage;}// Component "updateForm" bubbles up the PREPARE_FOR_RENDER event during// form rendervoid onPrepareForRenderFromUpdateForm() {try {course = courseFinderService.findCourseByUuid(courseUuid);} catch (ObjectNotFoundException e) {// Handle null course in the template.}// If the form has errors then we're redisplaying after a redirect.// Form will restore your input values but it's up to us to restore// Hidden values.if (updateForm.getHasErrors()) {if (course != null) {course.setVersion(versionFlash);}}}// Component "updateForm" bubbles up the PREPARE_FOR_SUBMIT event during for// submissionvoid onPrepareForSubmitFromUpdateForm() {// Get objects for the form fields to overlay.try {course = courseFinderService.findCourseByUuid(courseUuid);} catch (ObjectNotFoundException e) {course = new Course();updateForm.recordError("Course has been deleted by another process.");}}// Component "updateForm" bubbles up the VALIDATE event when it is submittedvoid onValidateFromUpdateForm() {if (updateForm.getHasErrors()) {// We get here only if a server-side validator detected an error.return;}try {courseManagerService.updateCourse(course, course.getName(), course.getSummary(), course.getDescription(), 1);} catch (RestClientFailureException e) {updateForm.recordError("Internal error on server.");updateForm.recordError(e.getMessage());} catch (Exception e) {// Display the cause. In a real system we would try harder to get a// user-friendly message.updateForm.recordError(ExceptionUtil.getRootCauseMessage(e));}}// Component "updateForm" bubbles up SUCCESS or FAILURE when it is// submitted, depending on whether VALIDATE// records an errorboolean onSuccessFromUpdateForm() {// We want to tell our containing page explicitly what course we've// updated, so we trigger new event// "successfulUpdate" with a parameter. It will bubble up because we// don't have a handler method for it.componentResources.triggerEvent(SUCCESSFUL_UPDATE, new Object[] { courseUuid }, null);// We don't want "success" to bubble up, so we return true to say we've// handled it.mode = Mode.REVIEW;return true;}boolean onFailureFromUpdateForm() {versionFlash = course.getVersion();// Rather than letting "failure" bubble up which doesn't say what you// were trying to do, we trigger new event// "failedUpdate". It will bubble up because we don't have a handler// method for it.componentResources.triggerEvent(FAILED_UPDATE, new Object[] { courseUuid }, null);// We don't want "failure" to bubble up, so we return true to say we've// handled it.return true;}
}

删除模板和Java

编辑器没有明确的“删除”模式，但确实支持删除审阅和更新页面上的当前对象。

// /// DELETE// /// Handle event "delete"Object onDelete(String courseUuid) {this.courseUuid = courseUuid;int courseVersion = 0;try {courseManagerService.deleteCourse(courseUuid, courseVersion);} catch (ObjectNotFoundException e) {// the object's already deleted} catch (RestClientFailureException e) {createForm.recordError("Internal error on server.");createForm.recordError(e.getMessage());// Display the cause. In a real system we would try harder to get a// user-friendly message.deleteMessage = ExceptionUtil.getRootCauseMessage(e);// Trigger new event "failedDelete" which will bubble up.componentResources.triggerEvent(FAILED_DELETE, new Object[] { courseUuid }, null);// We don't want "delete" to bubble up, so we return true to say// we've handled it.return true;} catch (Exception e) {// Display the cause. In a real system we would try harder to get a// user-friendly message.deleteMessage = ExceptionUtil.getRootCauseMessage(e);// Trigger new event "failedDelete" which will bubble up.componentResources.triggerEvent(FAILED_DELETE, new Object[] { courseUuid }, null);// We don't want "delete" to bubble up, so we return true to say// we've handled it.return true;}// Trigger new event "successfulDelete" which will bubble up.componentResources.triggerEvent(SUCCESFUL_DELETE, new Object[] { courseUuid }, null);// We don't want "delete" to bubble up, so we return true to say we've// handled it.return indexPage;}

下一步

显而易见的下一步是改进错误消息，增加对分页，支持以及一对多和多对多关系的支持。所有这些都需要修改REST负载。我在管道中还有一些其他项目，例如ExceptionService，更不用说安全问题了。

源代码

可从http://code.google.com/p/invariant-properties-blog/source/browse/student获取源代码。

参考： 项目学生： Invariant Properties博客上的JCG合作伙伴 Bear Giles提供的Maintenance Webapp（可编辑）。

翻译自: https://www.javacodegeeks.com/2014/02/project-student-maintenance-webapp-editable.html