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Applying conventions through the Visitor patternedit
It is also possible to apply a transformation on all or specific properties.
.AutoMap() internally implements the visitor pattern.
The default visitor, NoopPropertyVisitor, does nothing and acts as a blank canvas for you
to implement your own visiting methods.
For instance, let’s create a custom visitor that disables doc values for numeric and boolean types (Not really a good idea in practice, but let’s do it anyway for the sake of a clear example.)
Using the following two POCOs as in previous examples,
public class Company
{
public string Name { get; set; }
public List<Employee> Employees { get; set; }
}
public class Employee
{
public string FirstName { get; set; }
public string LastName { get; set; }
public int Salary { get; set; }
public DateTime Birthday { get; set; }
public bool IsManager { get; set; }
public List<Employee> Employees { get; set; }
public TimeSpan Hours { get; set; }
}
We first define a visitor; it’s easiest to inherit from NoopPropertyVisitor and override
the Visit methods to implement your conventions
public class DisableDocValuesPropertyVisitor : NoopPropertyVisitor
{
public override void Visit(
INumberProperty type,
PropertyInfo propertyInfo,
ElasticsearchPropertyAttributeBase attribute)
{
type.DocValues = false;
}
public override void Visit(
IBooleanProperty type,
PropertyInfo propertyInfo,
ElasticsearchPropertyAttributeBase attribute)
{
type.DocValues = false;
}
}
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Override the |
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Similarily, override the |
Now we can pass an instance of our custom visitor to .AutoMap()
var descriptor = new CreateIndexDescriptor("myindex")
.Mappings(ms => ms
.Map<Employee>(m => m.AutoMap(new DisableDocValuesPropertyVisitor()))
);
and any time the client maps a property of the POCO (Employee in this example) as a number (INumberProperty) or boolean (IBooleanProperty),
it will apply the transformation defined in each Visit() call respectively, which in this example
disables doc_values.
{
"mappings": {
"employee": {
"properties": {
"birthday": {
"type": "date"
},
"employees": {
"properties": {},
"type": "object"
},
"firstName": {
"type": "string"
},
"hours": {
"doc_values": false,
"type": "long"
},
"isManager": {
"doc_values": false,
"type": "boolean"
},
"lastName": {
"type": "string"
},
"salary": {
"doc_values": false,
"type": "integer"
}
}
}
}
}
Visiting on PropertyInfoedit
You can even take the visitor approach a step further, and instead of visiting on IProperty types, visit
directly on your POCO reflected PropertyInfo properties.
As an example, let’s create a visitor that maps all CLR types to an Elasticsearch string datatype (IStringProperty).
public class EverythingIsAStringPropertyVisitor : NoopPropertyVisitor
{
public override IProperty Visit(PropertyInfo propertyInfo, ElasticsearchPropertyAttributeBase attribute) => new StringProperty();
}
var descriptor = new CreateIndexDescriptor("myindex")
.Mappings(ms => ms
.Map<Employee>(m => m.AutoMap(new EverythingIsAStringPropertyVisitor()))
);
{
"mappings": {
"employee": {
"properties": {
"birthday": {
"type": "string"
},
"employees": {
"type": "string"
},
"firstName": {
"type": "string"
},
"isManager": {
"type": "string"
},
"lastName": {
"type": "string"
},
"salary": {
"type": "string"
},
"hours": {
"type": "string"
}
}
}
}
}