将JSON查询条件转换为MongoDB / Mongoose操作

Question

I am building an application in Angular 8 on the client side and NodeJS 12 with MongoDB 4 / Mongoose 5 on the server side.

I have a query generated by the Angular query builder module in JSON format. The JSON object will be sent to the backend via a POST request.

Question: How can the JSON query be converted into MongoDB operators to perform the database query?

Here's an example of a simple query generated by the Query Builder plugin. Note the requirement for multiple levels of "nested" AND / OR conditions.

{
  "condition": "and",
  "rules": [
    {
      "field": "Brief_D_Reactiedatum",
      "operator": "!=",
      "value": "Eventtoets_Fn"
    },
    {
      "condition": "or",
      "rules": [
        {
          "field": "Alleen_AO",
          "operator": "=",
          "value": "Parkeerreden"
        }
      ]
    }
  ]
}

Answer 1

You need to build MongoDB's $expr which is similar to the query that you're getting from Angular query builder module . Since the ruleSets can be nested you need to run your mapping function recursively. Below code probably doesn't cover every possible case but should give you a good introduction to get started with such mapping.

 let q = { "condition": "and", "rules": [ { "field": "Brief_D_Reactiedatum", "operator": "!=", "value": "Eventtoets_Fn" }, { "condition": "or", "rules": [ { "field": "Alleen_AO", "operator": "=", "value": "Parkeerreden" } ] } ] }; const conditions = { "and": "$and", "or": "$or" }; const operators = { "=": "$eq", "!=": "$ne", "<": "$lt", "<=": "$lte", ">": "$gt", ">=": "$gte" }; const mapRule = rule => ({ [operators[rule.operator]]: [ "$"+rule.field, rule.value ] }); const mapRuleSet = ruleSet => { return { [conditions[ruleSet.condition]]: ruleSet.rules.map( rule => rule.operator ? mapRule(rule) : mapRuleSet(rule) ) } }; let mongoDbQuery = { $expr: mapRuleSet(q) }; console.log(mongoDbQuery); 

Result expression can passed either to MongoDB's find method

db.col.find(mongoDbQuery);

or into $match pipeline stage:

db.col.aggregate([{ $match: mongoDbQuery }]);