HTML5 离线存储之Web SQL

时间:2015-08-08

  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2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 dataBaseOperator.executeReader= dataBaseOperator.executeNonQuery;
17 dataBaseOperator.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.rows
24      };
25 }

  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

function loadUserStory() {
   
try {
        _userStoryProvider.loadUserStories(
function (result) {
           
var _userStories= new Array();
           
for (var i= 0; i< result.rows.length; i++) {
               
var o= result.rows.item(i);
               
var _userStory= new userStory(o.id, o.name, o.role, o.ability, o.benefit, o.importance, o.estimate, o.notes);
                _userStories.push(_userStory);
            }
//...
    }
catch (error) {
        alert(
"_userStoryProvider.loadUserStories:" + error);
    }
}

  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
11    /* 添加用户故事*/
12     $("#btnAdd").click(function () {
13        var item= { role: $("#role").val(), ability: $("#ability").val(), benefit: $("#benefit").val(), name: $("#Name").val(), importance: $("#Importance").val(), estimate: $("#Estimate").val(), notes: $("#Notes").val() };
14        try {
15             _userStoryProvider.addUserStory(item.role, item.ability, item.benefit, item.name, item.importance, item.estimate, item.notes);
16             loadUserStory();
17         }catch (error) {
18             alert("_userStoryProvider.addUserStory:" + error);
19         }
20     });
21
22    /* 创建用户故事表*/
23     $("#btnCreateTable").click(function () {
24        try {
25             _userStoryProvider.createUserStoryTable();
26         }catch (error) {
27             alert("_userStoryProvider.createUserStoryTable:" + error);
28         }
29     });
30
31    /* 删除用户故事表*/
32     $("#btnDropTable").click(function () {
33        try {
34             _userStoryProvider.dropUserStoryTable();
35         }catch (error) {
36             alert("_userStoryProvider.dropUserStoryTable:" + error);
37         }
38     });
39 });
40
41 /* 加载用户故事*/
42 function loadUserStory() {
43    try {
44         _userStoryProvider.loadUserStories(function (result) {
45            var _userStories= new Array();
46            for (var i= 0; i< result.rows.length; i++) {
47                var o= result.rows.item(i);
48                var _userStory= new userStory(o.id, o.name, o.role, o.ability, o.benefit, o.importance, o.estimate, o.notes);
49                 _userStories.push(_userStory);
50             }
51
52            if (!_userStories)return;
53            var table= document.getElementById("user_story_table");
54            if (!table)return;
55            var _trs= table.getElementsByTagName("tr");
56            var _len= _trs.length;
57            for (var i= 0; i< _len; i++) {
58                 table.removeChild(_trs[i]);
59             }
60             {
61                var tr= document.createElement("tr");
62                 tr.setAttribute("class","product_backlog_row header");
63                 {
64                     tr.appendChild(CreateTd("id","id"));
65                     tr.appendChild(CreateTd("name","name"));
66                     tr.appendChild(CreateTd("importance","importance"));
67                     tr.appendChild(CreateTd("estimate","estimate"));
68                     tr.appendChild(CreateTd("description","role"));
69                     tr.appendChild(CreateTd("notes","notes"));
70                     tr.appendChild(CreateTd("delete","delete"));
71                 };
72                 table.appendChild(tr);
73             }
74            for (var i= 0; i< _userStories.length; i++) {
75                 CreateRow(table, _userStories[i]);
76             }
77         });
78     }catch (error) {
79         alert("_userStoryProvider.loadUserStories:" + error);
80     }
81 }
82 function CreateRow(table, userStory) {
83    if (!table)return;
84    if (!userStory)return;
85     {
86        var tr= document.createElement("tr");
87         tr.setAttribute("class","product_backlog_row");
88         {
89             tr.appendChild(CreateTd("id", userStory.id));
90             tr.appendChild(CreateTd("name", userStory.name));
91             tr.appendChild(CreateTd("importance", userStory.importance));
92             tr.appendChild(CreateTd("estimate", userStory.estimate));
93             tr.appendChild(CreateTd("description", userStory.role));
94             tr.appendChild(CreateTd("notes", userStory.notes));
95             tr.appendChild(CreateDeleteButton("delete_button", userStory.id));
96         };
97         table.appendChild(tr);
98     }
99 }
100 function CreateTd(name, value) {
101    var td= document.createElement("td");
102     td.setAttribute("class","user_story" + name);
103     td.innerText= value;
104    return td;
105 };
106 function CreateDeleteButton(name, id) {
107    var td= document.createElement("td");
108     td.setAttribute("class","user_story" + name);
109    /* 删除用户故事*/
110     td.innerHTML= "<a href="###" title="delete" onclick="javascript:_userStoryProvider.removeUserStory('" + id+ "');removeRow(this);">>>delete</a>";
111    return td;
112 }
113 function removeRow(obj) {
114     document.getElementById("user_story_table").deleteRow(obj.parentNode.parentNode.rowIndex);
115    //obj.parentNode.parentNode.removeNode(true);
116

  有一个小例子,点这里下载(占位,有点小毛病改好就放)

  看完代码复习下基本功课

  1,WindowDatabase接口,注意openDatabase方法

[Supplemental, NoInterfaceObject]
interface WindowDatabase {
  Database openDatabase(
in DOMString name,in DOMString version,in DOMString displayName,in unsignedlong estimatedSize,in optional DatabaseCallback creationCallback);
};
Window implements WindowDatabase;

[Supplemental, NoInterfaceObject]
interface WorkerUtilsDatabase {
  Database openDatabase(
in DOMString name,in DOMString version,in DOMString displayName,in unsignedlong estimatedSize,in optional DatabaseCallback creationCallback);
  DatabaseSync openDatabaseSync(
in DOMString name,in DOMString version,in DOMString displayName,in unsignedlong estimatedSize,in optional DatabaseCallback creationCallback);
};
WorkerUtils implements WorkerUtilsDatabase;

[Callback
=FunctionOnly, NoInterfaceObject]
interface DatabaseCallback {
 
void handleEvent(in Database database);
};

  2,SQLTransaction接口,关注executeSql方法

typedef sequence<any> ObjectArray;

interface SQLTransaction {
 
void executeSql(in DOMString sqlStatement,in optional ObjectArray arguments,in optional SQLStatementCallback callback,in optional SQLStatementErrorCallback errorCallback);
};

[Callback
=FunctionOnly, NoInterfaceObject]
interface SQLStatementCallback {
 
void handleEvent(in SQLTransaction transaction,in SQLResultSet resultSet);
};

[Callback
=FunctionOnly, NoInterfaceObject]
interface SQLStatementErrorCallback {
  boolean handleEvent(
in SQLTransaction transaction,in SQLError error);
};

  3,最后看下SQLResultSetRowList定义

interface SQLResultSetRowList {
 
readonly attribute unsignedlong length;
  getter any item(
in unsignedlong index);
};

  和SQLResultSet定义

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

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