mongodb - MongodDB with Java driver: How to find nested atributes and how to use "and" operator

Question

The collection:

{"_id":{"$oid":"5c7d656a82bb44be9e770a7e"},"name":"Harry Potter","species":"human","gender":"male","house":"Gryffindor","dateOfBirth":"31-07-1980","yearOfBirth":{"$numberInt":"1980"},"ancestry":"half-blood","eyeColour":"green","hairColour":"black","wand":{"wood":"holly","core":"phoenix feather","length":{"$numberInt":"11"}},"patronus":"stag","hogwartsStudent":true,"hogwartsStaff":false,"actor":"Daniel Radcliffe","alive":true,"image":"http://hp-api.herokuapp.com/images/harry.jpg"}
{"_id":{"$oid":"5c7d656a82bb44be9e770a7f"},"name":"Hermione Granger","species":"human","gender":"female","house":"Gryffindor","dateOfBirth":"19-09-1979","yearOfBirth":{"$numberInt":"1979"},"ancestry":"muggleborn","eyeColour":"brown","hairColour":"brown","wand":{"wood":"vine","core":"dragon heartstring","length":""},"patronus":"otter","hogwartsStudent":true,"hogwartsStaff":false,"actor":"Emma Watson","alive":true,"image":"http://hp-api.herokuapp.com/images/hermione.jpeg"}
{"_id":{"$oid":"5c7d656a82bb44be9e770a80"},"name":"Ron Weasley","species":"human","gender":"male","house":"Gryffindor","dateOfBirth":"01-03-1980","yearOfBirth":{"$numberInt":"1980"},"ancestry":"pure-blood","eyeColour":"blue","hairColour":"red","wand":{"wood":"willow","core":"unicorn tail-hair","length":{"$numberInt":"14"}},"patronus":"Jack Russell terrier","hogwartsStudent":true,"hogwartsStaff":false,"actor":"Rupert Grint","alive":true,"image":"http://hp-api.herokuapp.com/images/ron.jpg"}
{"_id":{"$oid":"5c7d656a82bb44be9e770a81"},"name":"Draco Malfoy","species":"human","gender":"male","house":"Slytherin","dateOfBirth":"05-06-1980","yearOfBirth":{"$numberInt":"1980"},"ancestry":"pure-blood","eyeColour":"grey","hairColour":"blonde","wand":{"wood":"hawthorn","core":"unicorn tail-hair","length":{"$numberInt":"10"}},"patronus":"","hogwartsStudent":true,"hogwartsStaff":false,"actor":"Tom Felton","alive":true,"image":"http://hp-api.herokuapp.com/images/draco.jpg"}
{"_id":{"$oid":"5c7d656a82bb44be9e770a82"},"name":"Minerva McGonagall","species":"human","gender":"female","house":"Gryffindor","dateOfBirth":"04-10-1925","yearOfBirth":{"$numberInt":"1925"},"ancestry":"","eyeColour":"","hairColour":"black","wand":{"wood":"","core":"","length":""},"patronus":"tabby cat","hogwartsStudent":false,"hogwartsStaff":true,"actor":"Dame Maggie Smith","alive":true,"image":"http://hp-api.herokuapp.com/images/mcgonagall.jpg"}
{"_id":{"$oid":"5c7d656a82bb44be9e770a83"},"name":"Cedric Diggory","species":"human","gender":"male","house":"Hufflepuff","dateOfBirth":"","yearOfBirth":{"$numberInt":"1977"},"ancestry":"","eyeColour":"grey","hairColour":"brown","wand":{"wood":"ash","core":"unicorn hair","length":{"$numberDouble":"12.25"}},"patronus":"","hogwartsStudent":true,"hogwartsStaff":false,"actor":"Robert Pattinson","alive":false,"image":"http://hp-api.herokuapp.com/images/cedric.png"}
{"_id":{"$oid":"5c7d656a82bb44be9e770a84"},"name":"Cho Chang","species":"human","gender":"female","house":"Ravenclaw","dateOfBirth":"","yearOfBirth":"","ancestry":"","eyeColour":"brown","hairColour":"black","wand":{"wood":"","core":"","length":""},"patronus":"swan","hogwartsStudent":true,"hogwartsStaff":false,"actor":"Katie Leung","alive":true,"image":"http://hp-api.herokuapp.com/images/cho.jpg"}
{"_id":{"$oid":"5c7d656a82bb44be9e770a85"},"name":"Severus Snape","species":"human","gender":"male","house":"Slytherin","dateOfBirth":"09-01-1960","yearOfBirth":{"$numberInt":"1960"},"ancestry":"half-blood","eyeColour":"black","hairColour":"black","wand":{"wood":"","core":"","length":""},"patronus":"doe","hogwartsStudent":false,"hogwartsStaff":true,"actor":"Alan Rickman","alive":false,"image":"http://hp-api.herokuapp.com/images/snape.jpg"}
{"_id":{"$oid":"5c7d656a82bb44be9e770a86"},"name":"Rubeus Hagrid","species":"half-giant","gender":"male","house":"Gryffindor","dateOfBirth":"06-12-1928","yearOfBirth":{"$numberInt":"1928"},"ancestry":"half-blood","eyeColour":"black","hairColour":"black","wand":{"wood":"oak","core":"","length":{"$numberInt":"16"}},"patronus":"","hogwartsStudent":false,"hogwartsStaff":true,"actor":"Robbie Coltrane","alive":true,"image":"http://hp-api.herokuapp.com/images/hagrid.png"}
{"_id":{"$oid":"5c7d656a82bb44be9e770a87"},"name":"Neville Longbottom","species":"human","gender":"male","house":"Gryffindor","dateOfBirth":"30-07-1980","yearOfBirth":{"$numberInt":"1980"},"ancestry":"pure-blood","eyeColour":"","hairColour":"blonde","wand":{"wood":"cherry","core":"unicorn tail-hair","length":{"$numberInt":"13"}},"patronus":"","hogwartsStudent":true,"hogwartsStaff":false,"actor":"Matthew Lewis","alive":true,"image":"http://hp-api.herokuapp.com/images/neville.jpg"}
{"_id":{"$oid":"5c7d656a82bb44be9e770a88"},"name":"Luna Lovegood","species":"human","gender":"female","house":"Ravenclaw","dateOfBirth":"13-02-1981","yearOfBirth":{"$numberInt":"1981"},"ancestry":"","eyeColour":"grey","hairColour":"blonde","wand":{"wood":"","core":"","length":""},"patronus":"hare","hogwartsStudent":true,"hogwartsStaff":false,"actor":"Evanna Lynch","alive":true,"image":"http://hp-api.herokuapp.com/images/luna.jpg"}
{"_id":{"$oid":"5c7d656a82bb44be9e770a89"},"name":"Ginny Weasley","species":"human","gender":"female","house":"Gryffindor","dateOfBirth":"11-08-1981","yearOfBirth":{"$numberInt":"1981"},"ancestry":"pure-blood","eyeColour":"brown","hairColour":"red","wand":{"wood":"yew","core":"","length":""},"patronus":"horse","hogwartsStudent":true,"hogwartsStaff":false,"actor":"Bonnie Wright","alive":true,"image":"http://hp-api.herokuapp.com/images/ginny.jpg"}
{"_id":{"$oid":"5c7d656a82bb44be9e770a8a"},"name":"Sirius Black","species":"human","gender":"male","house":"Gryffindor","dateOfBirth":"03-11-1959","yearOfBirth":{"$numberInt":"1959"},"ancestry":"pure-blood","eyeColour":"grey","hairColour":"black","wand":{"wood":"","core":"","length":""},"patronus":"hare","hogwartsStudent":false,"hogwartsStaff":false,"actor":"Gary Oldman","alive":false,"image":"http://hp-api.herokuapp.com/images/sirius.JPG"}
{"_id":{"$oid":"5c7d656a82bb44be9e770a8b"},"name":"Remus Lupin","species":"werewolf","gender":"male","house":"Gryffindor","dateOfBirth":"10-03-1960","yearOfBirth":{"$numberInt":"1960"},"ancestry":"half-blood","eyeColour":"green","hairColour":"brown","wand":{"wood":"cypress","core":"unicorn tail-hair","length":{"$numberDouble":"10.25"}},"patronus":"wolf","hogwartsStudent":false,"hogwartsStaff":true,"actor":"David Thewlis","alive":false,"image":"http://hp-api.herokuapp.com/images/lupin.jpg"}
{"_id":{"$oid":"5c7d656a82bb44be9e770a8c"},&qu

Answer 1

You were not sufficiently clear about what was the result of your approaches. Do they give execution errors or don't they bring the results you expected?

For the first problem, it seems that alive and hogwartsStudents are of boolean type, so I recommend to use true instead of "true"

FindIterable<Document> aliveStudents = harrypotter.find(and(eq("alive", true), eq("hogwartsStudent", true)));
System.out.println("---------- ALIVE STUDENTS ----------");
for (Object character : aliveStudents) {System.out.println(((Document) character).toJson());}

For the second problem, I think you should use the fieldName.fieldProperty syntax:

FindIterable<Document> wand= harrypotter.find(eq("wand.wood", "holly"));
System.out.println("---------- CHARACTERS WITH HOLLY WAND ----------");
for (Object character: wand) {System.out.println(((Document) character).toJson());}