一、投影表字段

投影只包含a_field和b_field字段

Aggregation aggregation= Aggregation.newAggregation(Aggregation.project("a_field", "b_field")); List<Map> list = mongoOperations.aggregate(aggregation, "table", Map.class).getMappedResults();

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二、投影排除字段

排除a_field和b_field字段，投影其他字段

Aggregation aggregation= Aggregation.newAggregation(Aggregation.project().andExclude("a_field", "b_field")); List<Map> list = mongoOperations.aggregate(aggregation, "table", Map.class).getMappedResults();

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三、投影表達(dá)式

時(shí)間毫秒time字段投影生成總秒數(shù)seconds和小時(shí)余數(shù)hourMod字段

Aggregation aggregation= Aggregation.newAggregation(Aggregation.project().and(ArithmeticOperators.Floor.floorValueOf(ArithmeticOperators.Divide.valueOf("time").divideBy(1000))).as("seconds").and(ArithmeticOperators.Mod.valueOf(ArithmeticOperators.Floor.floorValueOf(ArithmeticOperators.Divide.valueOf("time").divideBy(1000))).mod(24 * 60 * 60)).as("hourMod"));List<Map> list = mongoOperations.aggregate(aggregation, "table", Map.class).getMappedResults();

總結(jié)

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