原文网址：Spring Data MongoDB--MongoTemplate查询数据--方法/实例_IT利刃出鞘的博客-CSDN博客

简介

说明

        本文用示例介绍Spring Data MongoDB（MongoTemplate）查询数据的方法。

查询方法分类

• mongoTemplate.find  //返回list
• mongoTemplate.findOne  //返回1个（查询1个）
• mongoTemplate.findAll   // 返回list（查询所有）

简单查询

@Test
public void testEqual2() {
    // 使用静态方法创建 Criteria
    Criteria criteria = Criteria.where("press").is("清华大学出版社");

    Query query = new Query(criteria);
    final List<Book> books = mongoTemplate.find(query, Book.class, "book");
    assert books.size() == 3;
}

支持的查询有：

1. 等于：is
2. 大于：gt
3. 小于：lt
4. 大于等于：gte
5. 小于等于：lte
6. 不等于：ne
7. 模：mod 

多条件查询

@Test
public void testAnd() {
    Criteria criteria = new Criteria();
    criteria.and("price")
        .gt(45)
        .and("press").is("清华大学出版社");

    Query query = new Query(criteria);

    List<Book> books = mongoTemplate.find(query, Book.class, BOOK_COLLECTION);
}

排序与分页

@Test
public void testSortAndLimit() {
    Criteria criteria = Criteria.where("press").is("清华大学出版社");
    Query query = new Query(criteria);

    // with 方法设置排序
    query.with(Sort.by(Sort.Direction.ASC, "price"));
    // skip limit 方法设置分页
    query.skip(1).limit(10);

    final List<Book> books = mongoTemplate.find(query, Book.class, "book");
    assert  books.size() ==2;
}

正则查询

@Test
public void testContain(){
    String name = "开发";
    Pattern pattern = Pattern.compile("^.*" + name + ".*$", Pattern.CASE_INSENSITIVE);

    Criteria criteria = Criteria.where("name").regex(pattern);

    Query query = new Query(criteria);

    final List<Book> books = mongoTemplate.find(query, Book.class, "book");
    assert books.size() == 1;
}

数组查询

匹配数组中单个值

// 数组中包含查询单值
@Test
public void testArrayMatchSingle() {
    Criteria criteria = Criteria.where("tags").is("编程");

    Query query = new Query(criteria);

    List<Book> books = mongoTemplate.find(query, Book.class, "book");
}

匹配数组中多个值

// 数组中同时包含指定的多个值，不要求顺序
@Test
public void testArrayMatchAll() {
    Criteria criteria = Criteria.where("tags").all("编程", "程序设计");

    Query query = new Query(criteria);

    List<Book> books = mongoTemplate.find(query, Book.class, "book");
}

匹配数组中元素个数

@Test
public void testArrayMatchSize() {
    Criteria criteria = Criteria.where("tags").size(4);

    Query query = new Query(criteria);

    List<Book> books = mongoTemplate.find(query, Book.class, "book");
}

匹配指定位置元素

// 满足特定索引下条件
// 数组索引从 0 开始，匹配第二项就用 tags.1 作为键
@Test
public void testMatchIndex() {
    Criteria criteria = Criteria.where("tags.1").is("编程");

    Query query = new Query(criteria);

    List<Book> books = mongoTemplate.find(query, Book.class, "book");
}

匹配整个数组

// 元素个数和顺序都要匹配
@Test
public void testArrayMatch() {
    Criteria criteria = Criteria.where("tags").is(new String[]{"程序设计", "编程", "python"});

    Query query = new Query(criteria);

    List<Book> books = mongoTemplate.find(query, Book.class, "book");
}

匹配子文档

@Test
public void testMatchSubDoc() {
    Criteria criteria = Criteria.where("authors.name").is("纪涵");

    Query query = new Query(criteria);

    List<Book> books = mongoTemplate.find(query, Book.class, "book");
}

elementMatch

@Test
public void testElementMatch() {
    Criteria criteria = Criteria.where("authors").elemMatch(Criteria.where("name").is("谢希仁").and("sex").is("男"));

    Query query = new Query(criteria);

    List<Book> books = mongoTemplate.find(query, Book.class, "book");
}

聚合查询

count

@Test
public void testCount() {
    Query query = new Query();
    long ret = mongoTemplate.count(query, "book");
    System.out.println(ret);
}

distinct

@Test
public void testDistinct(){
    List<String> distinctPress = mongoTemplate
        .findDistinct(new Query(), "press", "book", String.class);
    System.out.println(distinctPress);
}

sum、count、avg

@Test
public void testSum() {
    Aggregation aggregation = Aggregation.newAggregation(
        Aggregation.project("_id", "press", "price"),
        Aggregation.group("press")
        .count().as("count")
        .sum("price").as("total")
        .avg("price").as("avg")
    );

    AggregationResults<Map> aggregationResults = mongoTemplate
        .aggregate(aggregation, "book", Map.class);
    List<Map> mappedResults = aggregationResults.getMappedResults();
    System.out.println(mappedResults);
}

带有表达式的计算

@Test
public void testSum2() {
    // 定义乘法表达式, 可以是两个字段相乘或者字段与数字相乘
    //同理，ArithmeticOperators 包含 加减乘除模等操作

    ArithmeticOperators.Multiply price = 
        ArithmeticOperators.valueOf("PRICE").multiplyBy(5);
   
    Aggregation aggregation = Aggregation.newAggregation(
        Aggregation.project("_id", "press", "PRICE"),
        Aggregation.group("press")
        .count().as("count")
        .sum(price).as("total")
        .avg(price).as("avg")
    );

    AggregationResults<Map> aggregationResults = mongoTemplate
        .aggregate(aggregation, "book", Map.class);
    List<Map> mappedResults = aggregationResults.getMappedResults();
    System.out.println(mappedResults);
}