第四节 MongoDB复杂及变化对象的存储

本节探讨问题：

• 复杂对象的存储
• 存储的实体对象发生变化了

     既然要使MongoDB做业务驱动开发，那就要考虑到复杂的对象是否容易可以直接序列化存储呢？在后期的开发中，总会碰到对象的会增加或删除属性，那对象属性变动了，是否会对之前的存到MongoDB的数据反序列化会有影响呢？接下来我们就带着这些问题来简单测试一下，我也不知道是否会有问题。

一、复杂对象的存储

我们先来测试一些值类型的序列化问题，.net mvc中有两个方法用来将前台传回的数据绑定到对象上，TryUpdateModel(),UpdateModel(),我记得碰到日期，值类型若没赋值都会出错。而其它的序列化对数组，HashTable,日期等都要单独处理。我们来看一MongoDB是怎么处理的

  1.带参构造函数的类 

class Program
{
public class Employee
{
public string Name { set; get; }
public int Age { set; get; }
public bool Sex { set; get; }
public DateTime Birthday { set; get; }
public JobBase Job { set; get; }
public Hashtable HT { set; get; }
}

public class Company
{
public string Name { set; get; }
public DateTime CreateDate { set; get; }
public List<Employee> EmployeeCollection { set; get; }
public string[] Department { set; get; }
public double Rate { set; get; }
}

public class JobBase
{ 
public string Name { set; get; }
public Work Work { set; get; }
public void Action()
{
Console.WriteLine("我是" + this.Name);
}
}

public class Work
{
private string something;
public Work(string something)
{
this.something = something;
}

public void ToDo()
{
Console.WriteLine("我喜欢做" + something);
}
}


static void Main(string[] args)
{
Mongo mongo = new Mongo("Server=127.0.0.1:27017");
mongo.Connect();

IMongoDatabase simple = mongo["simple"];
var compCollection = simple.GetCollection<Company>();

//Company company = new Company();
//company.CreateDate = DateTime.Now;
//company.Name = "C Company";
//company.Department = new string[] { "信息部", "财务部", "开发部" };

var empCollection = simple.GetCollection<Employee>();

Employee employee1 = new Employee() { Name = "llj", Age = 24, Sex = true, Birthday = new DateTime(1984, 9, 9) };
employee1.Job = new JobBase() { Name = "IT" };
employee1.Job.Work = new Work("IT杂志");
employee1.HT = new Hashtable();
employee1.HT.Add("A1", "AA1");
Employee employee2 = new Employee() { Name = "cctv", Sex = true, Birthday = new DateTime(1984, 9, 9) };
employee2.Job = new JobBase() { Name = "TEST" };
employee2.Job.Work = new Work("TEST测试"); 
employee2.HT = new Hashtable();
employee2.HT.Add("B1", "BB1");
Employee employee3 = new Employee() { Name = "http", Age = 24, Sex = true };
employee3.Job = new JobBase() { Name = "DEV" };
employee3.Job.Work = new Work("DEV开发"); 
employee3.HT = new Hashtable();
employee3.HT.Add("C3", "CC3");

//company.EmployeeCollection = new List<Employee>();
//company.EmployeeCollection.Add(employee1);
//company.EmployeeCollection.Add(employee2);
//company.EmployeeCollection.Add(employee3); 
//compCollection.Save(company);

empCollection.Save(employee1);
empCollection.Save(employee2);
empCollection.Save(employee3);

Console.WriteLine("Count: {0}", empCollection.Linq().Count());
//选择一个对象查看
Employee employee=empCollection.FindOne(new Document{{"Name","llj"}});

//Company companyNew = compCollection.FindOne(new Document{{"Name","C Company"}});
//companyNew.EmployeeCollection[0].Job.Action();
//companyNew.EmployeeCollection[0].Job.Work.ToDo();
mongo.Disconnect();
mongo.Dispose();
Console.ReadLine();
}
}

程序出错了，原因是Work这个类是带参的构造函数的，也说你的对象是通过带参的构造函数创建的被保存Mongo中，再反射回来时会出错的。见下面

我们注掉Work类的所有代码，继续测试 db.Employee.drop()

2.值类型及日期的测试 

class Program
{
public class Employee
{
public string Name { set; get; }
public int Age { set; get; }
public bool Sex { set; get; }
public DateTime Birthday { set; get; }
public JobBase Job { set; get; }
public Hashtable HT { set; get; }
}

public class Company
{
public string Name { set; get; }
public DateTime CreateDate { set; get; }
public List<Employee> EmployeeCollection { set; get; }
public string[] Department { set; get; }
public double Rate { set; get; }
}

public class JobBase
{ 
public string Name { set; get; } 
public void Action()
{
Console.WriteLine("我是" + this.Name);
}
} 


static void Main(string[] args)
{
Mongo mongo = new Mongo("Server=127.0.0.1:27017");
mongo.Connect();

IMongoDatabase simple = mongo["simple"];
var compCollection = simple.GetCollection<Company>();

//Company company = new Company();
//company.CreateDate = DateTime.Now;
//company.Name = "C Company";
//company.Department = new string[] { "信息部", "财务部", "开发部" };

var empCollection = simple.GetCollection<Employee>();

Employee employee1 = new Employee() { Name = "llj", Age = 24, Sex = true, Birthday = new DateTime(1984, 9, 9) };
employee1.Job = new JobBase() { Name = "IT" }; 
employee1.HT = new Hashtable();
employee1.HT.Add("A1", "AA1");
Employee employee2 = new Employee() { Name = "cctv", Sex = true, Birthday = new DateTime(1984, 9, 9) };
employee2.Job = new JobBase() { Name = "TEST" }; ; 
employee2.HT = new Hashtable();
employee2.HT.Add("B1", "BB1");
Employee employee3 = new Employee() { Name = "http", Age = 24, Sex = true };
employee3.Job = new JobBase() { Name = "DEV" }; 
employee3.HT = new Hashtable();
employee3.HT.Add("C3", "CC3");

//company.EmployeeCollection = new List<Employee>();
//company.EmployeeCollection.Add(employee1);
//company.EmployeeCollection.Add(employee2);
//company.EmployeeCollection.Add(employee3); 
//compCollection.Save(company);

empCollection.Save(employee1);
empCollection.Save(employee2);
empCollection.Save(employee3);

Console.WriteLine("Count: {0}", empCollection.Linq().Count());
//选择一个对象查看
Employee employee=empCollection.FindOne(new Document{{"Name","llj"}});

//Company companyNew = compCollection.FindOne(new Document{{"Name","C Company"}});
//companyNew.EmployeeCollection[0].Job.Action(); 
mongo.Disconnect();
mongo.Dispose();
Console.ReadLine();
}
}

查看结果：

我们可以看到，未设置年龄，日期的字段，Mongo都会处理为0和一个指定日期，而HashTable也是可以被自动序列化进来的。

那再把看一下取出来的对象被还原成什么样了，

3.组合子对象，增加集合测试

class Program
{
public class Employee
{
public string Name { set; get; }
public int Age { set; get; }
public bool Sex { set; get; }
public DateTime Birthday { set; get; }
public JobBase Job { set; get; }
public Hashtable HT { set; get; }
}

public class Company
{
public string Name { set; get; }
public DateTime CreateDate { set; get; }
public List<Employee> EmployeeCollection { set; get; }
public string[] Department { set; get; }
public double Rate { set; get; }
}

public class JobBase
{ 
public string Name { set; get; } 
public void Action()
{
Console.WriteLine("我是" + this.Name);
}
} 


static void Main(string[] args)
{
Mongo mongo = new Mongo("Server=127.0.0.1:27017");
mongo.Connect();

IMongoDatabase simple = mongo["simple"];
var compCollection = simple.GetCollection<Company>();

Company company = new Company();
company.CreateDate = DateTime.Now;
company.Name = "C Company";
company.Department = new string[] { "信息部", "财务部", "开发部" };

Employee employee1 = new Employee() { Name = "llj", Age = 24, Sex = true, Birthday = new DateTime(1984, 9, 9) };
employee1.Job = new JobBase() { Name = "IT" };
employee1.HT = new Hashtable();
employee1.HT.Add("A1", "AA1");
Employee employee2 = new Employee() { Name = "cctv", Sex = true, Birthday = new DateTime(1984, 9, 9) };
employee2.Job = new JobBase() { Name = "TEST" }; ;
employee2.HT = new Hashtable();
employee2.HT.Add("B1", "BB1");
Employee employee3 = new Employee() { Name = "http", Age = 24, Sex = true };
employee3.Job = new JobBase() { Name = "DEV" };
employee3.HT = new Hashtable();
employee3.HT.Add("C3", "CC3");

company.EmployeeCollection = new List<Employee>();
company.EmployeeCollection.Add(employee1);
company.EmployeeCollection.Add(employee2);
company.EmployeeCollection.Add(employee3);
compCollection.Save(company);

Company companyNew = compCollection.FindOne(new Document { { "Name", "C Company" } });
companyNew.EmployeeCollection[0].Job.Action(); 
mongo.Disconnect();
mongo.Dispose();
Console.ReadLine();
}
}

看一下结果:

可以看到List集合，字符串数组，组合类都已成功序列化保存到Mongo中了，那我们在还从Mongo把这个对象取出来

对象被成功的还原回来了，那我们修改现在的对象属性，去掉Company的Department属性，以及Employee的JobBase属性看看还原后的情况

4.增删属性再还原对象

public class Employee
{
public string Name { set; get; }
public int Age { set; get; }
public bool Sex { set; get; }
public DateTime Birthday { set; get; }
//public JobBase Job { set; get; }
public Hashtable HT { set; get; }
}

public class Company
{
public string Name { set; get; }
public DateTime CreateDate { set; get; }
public List<Employee> EmployeeCollection { set; get; }
//public string[] Department { set; get; }
public double Rate { set; get; }
}

查看结果，看看是否会影响对象成功还原

对象成功还原了，少掉那部分属性。那我们再将对象保存回去，看看Mongo会将那部分多出来的属性丢弃吗？为了表现明显，我们将Company的List属性也注释掉

执行以下代码

Company companyNew = compCollection.FindOne(new Document { { "Name", "C Company" } });
compCollection.Update(companyNew, companyNew);

查看结果Mongo中的结果：

 

读取后的对象被保存回去会将原先的多出的属性数据丢弃。

总结：经过测试，Mongo可存取复杂的对象（对象中不包含其它带参构造函数，影响到还原），包括数组，泛型集合，哈希表，值类型等等。非空字段Mongo会自动匹配一些特定的值。但是当对象本身发生变化了，比如删除属性后，读取后再更新回去，会导致原先的多出的属性丢失，因此开发中要考虑到对象变了之后，之前的数据是否要保留下来，做好备份。Mongo要求存储的对象要尽量相对稳定或者结构相对简单，否则前期的业务对象设计要花大量时间了。