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#MDBlocal
Just in Time Validation with
JSON Schema
#MDBlocal
Shannon Bradshaw
VP of Developer Education,
Snowboarding Enthusiast, Father
MongoDB
@shannonbradshaw
#MDBlocal
$jsonSchema
#MDBlocal
Flexible
SchemaRigid
Schema
Your App
#MDBlocal
Flexible
SchemaRigid
Schema
Your App
risk
success!
regulation
policy
politics
#MDBlocal
Flexible
SchemaRigid
Schema
Your App
risk
success!
regulation
policy
politics
Production
Concerns
#MDBlocal
#MDBlocal
{
_id: 34556,
item: "Flannel T-shirt",
price: NumberDecimal("27.99"),
quantity: NumberInt(1)
color: "green"
}
Simple Schema to Start
#MDBlocal
Document Validation (v3.2)Use query filters to define schema constraints. E.g.,
db.createCollection("orders", {
validator: {
item: {$type: "string"},
price: {$type: "decimal"},
quantity: {$type: "int"},
color: {$in: ["red", "green", "blue"]}
}
});
(ex1 - ex6)
#MDBlocal
JSON Schema (v3.6)
● JSON Schema Draft 04
● Is becoming an industry standard
● Widely used; lots of community support
(ex5)
#MDBlocal
Flexible
SchemaRigid
Schema
Our App
#MDBlocal
(ex6 - ex8b)
Let's make our validator a little
more strict
#MDBlocal
Good for Starter Examples
{
_id: 34556,
item: "Flannel T-shirt",
price: NumberDecimal("27.99"),
quantity: NumberLong(1),
color: "green"
}
{
_id: 34556,
total: NumberDecimal("141.00"),
VAT: NumberDecimal("0.20"),
totalWithVAT: NumberDecimal("169.20"),
lineitems: [
{ sku: "MDBTS001",
name: "Flannel T-shirt",
quantity: 10,
unit_price: NumberDecimal("9.00") },
{ sku: "MDBTS002",
quantity: 5,
unit_price: NumberDecimal("10.00")}]
}
More Realistic
#MDBlocal
Good for Starter Examples
{
_id: 34556,
item: "Flannel T-shirt",
price: NumberDecimal("27.99"),
quantity: NumberLong(1),
color: "green"
}
{
_id: 34556,
total: NumberDecimal("141.00"),
VAT: NumberDecimal("0.20"),
totalWithVAT: NumberDecimal("169.20"),
lineitems: [
{ sku: "MDBTS001",
name: "Flannel T-shirt",
quantity: 10,
unit_price: NumberDecimal("9.00") },
{ sku: "MDBTS002",
quantity: 5,
unit_price: NumberDecimal("10.00")}]
}
More Realistic
#MDBlocal
Our New Orders Schema
● Orders must contain a lineitems array of 1 to 10 documents
● Documents embedded in lineitems have fields for:
○ sku (required)
○ name (optional)
○ unit_price (required)
○ quantity (required)
● Value of quantity must be an integer
● (Must also contain fields: total, VAT, totalWithVAT, but we'll get to that.)
#MDBlocal
Let's validate the line item documents
(embedded in an array)
(ex9 - 10b)
#MDBlocal
Now Let's Deal with Totals and VAT
The most recent order we looked at actually contains a few errors:● The totalWithVAT value should be 141 * 1.20 = 169.2
● The total value should be the sum of each line item sub-total
● I.e., (10 * 9) + (10 * 5) = 140
Can we enforce that totalWithVAT and total are correct using validation?
#MDBlocal
Yes we can!
● MongoDB 3.6 -- more expressive query syntax
● Can express complex business rules in validations
● E.g, compute and compare multiple values at runtime
#MDBlocal
$expr
Check that totalWithVAT == total * (1+VAT):
$expr: {
$eq: [
"$totalWithVAT",
{$multiply: [
"$total",
{$sum: [1, "$VAT"]}
]}
]
}
Let's add this as a validation rule alongside our JSON Schema validation ()
#MDBlocal
Now let's make sure the total is the
sum of the line item subtotals
#MDBlocal
Ensure total equals sum of line items$expr: {
$eq: [
"$total",
{$sum: {
$map: {
"input": "$lineitems",
"as": "item",
"in": {
"$multiply": [
"$$item.quantity",
"$$item.unit_price"
] } } }} ] }
#MDBlocal
All together now
(ex11 - 14c)
#MDBlocal
Flexible
SchemaRigid
Schema
Our App
#MDBlocal
Flexible
SchemaRigid
Schema
risk
success!
regulation
policy
politics
Our App
#MDBlocal
Flexible
SchemaRigid
Schema
risk
success!
regulation
policy
politics
Our App
Production
Concerns
#MDBlocal
Special thanks to Raphael Londner
#MDBlocal
Learn More
● What's New Guide
● MongoDB Documentation
○ Schema Validation
○ Expressive Query Syntax
● Free MongoDB 3.6 Online Course from MongoDB University
