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HTML5离线存储之WebSQL

时间:2021-07-01 10:21:17 帮助过:3人阅读

本篇没有考虑异步,多线程及SQL注入

WebDatabase 规范中说这份规范不再维护了,原因是同质化(几乎实现者都选择了Sqlite),

且不说这些,单看在HTML5中如何实现离线数据的CRUD,最基本的用法(入门级别)

1,打开数据库

2,创建表

3,新增数据

4,更新数据

5,读取数据

6,删除数据

事实上,关键点在于如何拿到一个可执行SQL语句的上下文,

像创建表,删除表,CRUD操作等仅区别于SQL语句的写法.OK,貌似"SqlHelper"啊,换个名字,dataBaseOperator就它了

executeReader,executeScalar两个方法与executeNonQuery严重同质,

下边的代码产生定义了我们的dataBaseOperator"类",第二行

3-5行则定义打开数据库连接方法,"类方法",效果类似C#中的静态方法,直接类名.方法调用

6-15行则定义executeNonQuery方法,意指查询数据库,与executeReader方法和executeScalar方法同质,均可返回记录集

整个 dataBaseOperator就完整了,很简单,唯一要指出的是,测试以下代码时请选择一个支持HTML5的浏览器!如Google Chrome

  1. //TODO;SQL注入
  2. function dataBaseOperator() {};
  3. dataBaseOperator.openDatabase = function () {
  4. return window.openDatabase("dataBaseUserStories", "1.0", "dataBase used for user stories", 2 * 1024 * 1024);
  5. }
  6. dataBaseOperator.executeNonQuery = function (sql, parameters, callback) {
  7. var db = this.openDatabase();
  8. db.transaction(function (trans) {
  9. trans.executeSql(sql, parameters, function (trans, result) {
  10. callback(result);
  11. }, function (trans, error) {
  12. throw error.message;
  13. });
  14. });
  15. }
  16. dataBaseOperatordataBaseOperator.executeReader = dataBaseOperator.executeNonQuery;
  17. dataBaseOperatordataBaseOperator.executeScalar = dataBaseOperator.executeNonQuery;

有了"SqlHeper",再看业务处理层(Business Logic Layer)

业务处理类包括了创建表,删除表,新增记录,删除记录以及读取记录,这里没有写更新,实际上先删后增一样滴,即使要写也不复杂

  1. function userStoryProvider() {
  2. this.createUserStoryTable = function () {
  3. dataBaseOperator.executeNonQuery("CREATE TABLE tbUserStories(id integer primary key autoincrement,role,ability,benefit,name,importance,estimate,notes)");
  4. };
  5. this.dropUserStoryTable = function () {
  6. dataBaseOperator.executeNonQuery("DROP TABLE tbUserStories");
  7. };
  8. this.addUserStory = function (role, ability, benefit, name, importance, estimate, notes) {
  9. dataBaseOperator.executeNonQuery("INSERT INTO tbUserStories(role,ability,benefit,name,importance,estimate,notes) SELECT ?,?,?,?,?,?,?",
  10. [role, ability, benefit, name, importance, estimate, notes], function (result) {
  11. //alert("rowsAffected:" + result.rowsAffected);
  12. });
  13. };
  14. this.removeUserStory = function (id) {
  15. dataBaseOperator.executeNonQuery("DELETE FROM tbUserStories WHERE id = ?", [id], function (result) {
  16. //alert("rowsAffected:" + result.rowsAffected);
  17. });
  18. };
  19. this.loadUserStories = function (callback) {
  20. dataBaseOperator.executeReader("SELECT * FROM tbUserStories", [], function (result) {
  21. callback(result);
  22. });
  23. //result.insertId,result.rowsAffected,result.rows24 };
  24. }

createUserStoryTable,dropUserStoryTable,addUserStory,removeUserStory又是严重同质,不说了,仅SQL语句不同而已

但loadUserStories与上述四个方法均不同,是因为它把SQLResultSetRowList返回给了调用者,这里仍然是简单的"转发",页面在使用的时候需要首先创建provider实例(使用类似C#中的类实例上的方法调用)

  1. var _userStoryProvider = new userStoryProvider();

之后就可以调用该实例的方法了,仅举个例子,具体代码省去

  1. function loadUserStory() {
  2. try {
  3. _userStoryProvider.loadUserStories(function (result) {
  4. var _userStories = new Array();
  5. for (var i = 0; i < result.rows.length; i++) {
  6. var o = result.rows.item(i);
  7. var _userStory = new userStory(o.id, o.name, o.role, o.ability, o.benefit, o.importance, o.estimate, o.notes);
  8. _userStories.push(_userStory);
  9. }//...
  10. } catch (error) {
  11. alert("_userStoryProvider.loadUserStories:" + error);
  12. }}

得到_userStories这个数组后,就没有下文了,是自动创建HTML还是绑定到EXT,发挥想象力吧...继续

userStory是一个自定义的"Model" "类"·

  1. function userStory(id, name, role, ability, benefit, importance, estimate, notes) {
  2. this.id = id;
  3. this.name = name;
  4. this.role = role;
  5. this.ability = ability;
  6. this.benefit = benefit;
  7. this.importance = importance;
  8. this.estimate = estimate;
  9. this.notes = notes;
  10. };

最后贴出应用的代码,业务相关的代码,不看也罢,谁家与谁家的都不同

  1. /*
  2. http://stackoverflow.com/questions/2010892/storing-objects-in-html5-localstorage
  3. http://www.w3.org/TR/webdatabase/#sqlresultset
  4. http://html5doctor.com/introducing-web-sql-databases/
  5. http://stackoverflow.com/questions/844885/sqlite-insert-into-with-unique-names-getting-id
  6. */
  7. var _userStoryProvider = new userStoryProvider();
  8. $(document).ready(function () {
  9. loadUserStory();
  10. /* 添加用户故事 */
  11. $("#btnAdd").click(function () {
  12. var item = { role: $("#role").val(), ability: $("#ability").val(), benefit: $("#benefit").val(), name: $("#Name").val(), importance: $("#Importance").val(), estimate: $("#Estimate").val(), notes: $("#Notes").val() };
  13. try {
  14. _userStoryProvider.addUserStory(item.role, item.ability, item.benefit, item.name, item.importance, item.estimate, item.notes);
  15. loadUserStory();
  16. } catch (error) {
  17. alert("_userStoryProvider.addUserStory:" + error);
  18. }
  19. });
  20. /* 创建用户故事表 */
  21. $("#btnCreateTable").click(function () { try {
  22. _userStoryProvider.createUserStoryTable();
  23. } catch (error) {
  24. alert("_userStoryProvider.createUserStoryTable:" + error);
  25. }
  26. });
  27. /* 删除用户故事表 */
  28. $("#btnDropTable").click(function () {
  29. try {
  30. _userStoryProvider.dropUserStoryTable();
  31. } catch (error) {
  32. alert("_userStoryProvider.dropUserStoryTable:" + error);
  33. }
  34. });
  35. });
  36. /* 加载用户故事 */
  37. function loadUserStory() {
  38. try {
  39. _userStoryProvider.loadUserStories(function (result) {
  40. var _userStories = new Array();
  41. for (var i = 0; i < result.rows.length; i++) {
  42. var o = result.rows.item(i);
  43. var _userStory = new userStory(o.id, o.name, o.role, o.ability, o.benefit, o.importance, o.estimate, o.notes);
  44. _userStories.push(_userStory);
  45. }
  46. if (!_userStories) return;
  47. var table = document.getElementById("user_story_table");
  48. if (!table) return;
  49. var _trs = table.getElementsByTagName("tr");
  50. var _len = _trs.length;
  51. for (var i = 0; i < _len; i++) {
  52. table.removeChild(_trs[i]);
  53. }
  54. {
  55. var tr = document.createElement("tr");
  56. tr.setAttribute("class", "product_backlog_row header");
  57. {
  58. tr.appendChild(CreateTd("id", "id"));
  59. tr.appendChild(CreateTd("name", "name"));
  60. tr.appendChild(CreateTd("importance", "importance"));
  61. tr.appendChild(CreateTd("estimate", "estimate"));
  62. tr.appendChild(CreateTd("description", "role"));
  63. tr.appendChild(CreateTd("notes", "notes"));
  64. tr.appendChild(CreateTd("delete", "delete"));
  65. };
  66. table.appendChild(tr);
  67. }
  68. for (var i = 0; i < _userStories.length; i++) {
  69. CreateRow(table, _userStories[i]);
  70. }
  71. });
  72. } catch (error) {
  73. alert("_userStoryProvider.loadUserStories:" + error);
  74. }
  75. }
  76. function CreateRow(table, userStory) {
  77. if (!table) return;
  78. if (!userStory) return;
  79. {
  80. var tr = document.createElement("tr");
  81. tr.setAttribute("class", "product_backlog_row");
  82. {
  83. tr.appendChild(CreateTd("id", userStory.id));
  84. tr.appendChild(CreateTd("name", userStory.name));
  85. tr.appendChild(CreateTd("importance", userStory.importance));
  86. tr.appendChild(CreateTd("estimate", userStory.estimate));
  87. tr.appendChild(CreateTd("description", userStory.role));
  88. tr.appendChild(CreateTd("notes", userStory.notes));
  89. tr.appendChild(CreateDeleteButton("delete_button", userStory.id));
  90. };
  91. table.appendChild(tr);
  92. }
  93. }
  94. function CreateTd(name, value) {
  95. var td = document.createElement("td");
  96. td.setAttribute("class", "user_story " + name);
  97. td.innerText = value;
  98. return td;
  99. };
  100. function CreateDeleteButton(name, id) {
  101. var td = document.createElement("td");
  102. td.setAttribute("class", "user_story " + name);
  103. /* 删除用户故事 */
  104. td.innerHTML = "###\" title=\"delete\" onclick=\"javascript:_userStoryProvider.removeUserStory(\'" + id + "');removeRow(this);\">>>deletea>";
  105. return td;
  106. }
  107. function removeRow(obj) {
  108. document.getElementById("user_story_table").deleteRow(obj.parentNode.parentNode.rowIndex);
  109. //obj.parentNode.parentNode.removeNode(true);
  110. }

看完代码复习下基本功课

1,WindowDatabase接口,注意openDatabase方法

  1. [Supplemental, NoInterfaceObject]
  2. interface WindowDatabase {
  3. Database openDatabase(in DOMString name, in DOMString version, in DOMString displayName, in unsigned long estimatedSize, in optional DatabaseCallback creationCallback);};
  4. Window implements WindowDatabase;
  5. [Supplemental, NoInterfaceObject]
  6. interface WorkerUtilsDatabase {
  7. Database openDatabase(in DOMString name, in DOMString version, in DOMString displayName, in unsigned long estimatedSize, in optional DatabaseCallback creationCallback); DatabaseSync openDatabaseSync(in DOMString name, in DOMString version, in DOMString displayName, in unsigned long estimatedSize, in optional DatabaseCallback creationCallback);};
  8. WorkerUtils implements WorkerUtilsDatabase;
  9. [Callback=FunctionOnly, NoInterfaceObject]
  10. interface DatabaseCallback {
  11. void handleEvent(in Database database);
  12. };

2,SQLTransaction接口,关注executeSql方法

  1. typedef sequence<any> ObjectArray;
  2. interface SQLTransaction {
  3. void executeSql(in DOMString sqlStatement, in optional ObjectArray arguments, in optional SQLStatementCallback callback, in optional SQLStatementErrorCallback errorCallback);};
  4. [Callback=FunctionOnly, NoInterfaceObject]
  5. interface SQLStatementCallback {
  6. void handleEvent(in SQLTransaction transaction, in SQLResultSet resultSet);};
  7. [Callback=FunctionOnly, NoInterfaceObject]
  8. interface SQLStatementErrorCallback {
  9. boolean handleEvent(in SQLTransaction transaction, in SQLError error);
  10. };

3,最后看下SQLResultSetRowList定义

  1. interface SQLResultSetRowList {
  2. readonly attribute unsigned long length;
  3. getter any item(in unsigned long index);
  4. };

和SQLResultSet定义

  1. interface SQLResultSet {
  2. readonly attribute long insertId;
  3. readonly attribute long rowsAffected;
  4. readonly attribute SQLResultSetRowList rows;
  5. };

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