MongodbTemplate的查询操作

刺骨的言语ヽ痛彻心扉 2022-06-07 02:26 464阅读 0赞

Class类

@Document(collection = "class")
    public class Class { 
    
        private String classId;
        private String teacher;
        private List<Student> Students;
        public String getClassId() {
            return classId;
        }
        public void setClassId(String classId) {
            this.classId = classId;
        }
        public String getTeacher(){
            return teacher;
        }
        public void setTeacher(String teacher){
            this.teacher = teacher;
        }
        public List<Student> getStudents() {
            return Students;
        }
        public void setStudents(List<Student> Students) {
            this.Students = Students;
        }
        @Override
        public String toString() {
            return "Class [classId=" + classId + ", Students=" + Students + "]";
        }
    }

**查询满足条件的数据**

Query query = Query.query(Criteria.where("classId").is("1"));
    List<Class> classs = mongoTemplate.find(query,Class.class,"class");
    System.out.println(classs);

**查询满足条件的第一条数据**

Query query = Query.query(Criteria.where("classId").is("1"));
    List<Class> classs = mongoTemplate.findOne(query,Class.class,"class");
    System.out.println(classs);

**筛选要查询的字段（id字段不查出来）**

DBObject dbObject = new BasicDBObject();
    dbObject.put("classId", "1");
    DBObject fieldObject = new BasicDBObject();
    fieldObject.put("_id", false);
    Query query = new BasicQuery(dbObject, fieldObject);
    List<HashMap> classs = mongoTemplate.find(query,HashMap.class,"class");
    System.out.println(classs);

当然也可以不使用HashMap,而使用自己封装的dto，那么只会查询出dto中的字段。  
**查询结果排序**

DBObject dbObject = new BasicDBObject();
    dbObject.put("classId", "1");
    DBObject fieldObject = new BasicDBObject();
    fieldObject.put("_id", false);
    Query query = new BasicQuery(dbObject);
    query.with(new Sort(Direction.ASC,"classId"));
    List<HashMap> classs = mongoTemplate.find(query,HashMap.class,"class");
    System.out.println(classs);

**多字段排序**

DBObject dbObject = new BasicDBObject();
    dbObject.put("classId", "1");
    DBObject fieldObject = new BasicDBObject();
    fieldObject.put("_id", false);
    Query query = new BasicQuery(dbObject);
    List<Sort.Order> orders = new ArrayList<>();
    orders.add(new Sort.Order(Direction.DESC, "classId"));
    orders.add(new Sort.Order(Direction.DESC, "teacher"));
    query.with(new Sort(orders));
    List<HashMap> classs = mongoTemplate.find(query,HashMap.class,"class");
    System.out.println(classs);

**查询结果分页**

int pageNum = 1;
    int pageSize = 10;
    DBObject dbObject = new BasicDBObject();
    dbObject.put("classId", "1");
    DBObject fieldObject = new BasicDBObject();
    fieldObject.put("_id", false);
    Query query = new BasicQuery(dbObject,fieldObject);
    List<Sort.Order> orders = new ArrayList<>();
    orders.add(new Sort.Order(Direction.ASC, "classId"));
    orders.add(new Sort.Order(Direction.DESC, "teacher"));
    query.with(new Sort(orders));
    query.skip(pageSize*(pageNum-1)).limit(pageSize);
    List<HashMap> classs = mongoTemplate.find(query,HashMap.class,"class");
    System.out.println(classs);

还有一种通过Morphia框架的做法：

int pageNum = 1;
    int pageSize = 10;
    DBObject dbObject = new BasicDBObject();
    dbObject.put("teacher", "Mr.wang");
    DBObject fieldObject = new BasicDBObject();
    fieldObject.put("_id", false);
    fieldObject.put("_class", false);
    DBObject sortDBObject=new BasicDBObject(); 
       sortDBObject.put("classId",1); 
    DBCursor result = mongoTemplate.getCollection("class")
        .find(dbObject, fieldObject)
        .sort(sortDBObject)
        .skip(pageSize*(pageNum-1)).limit(pageSize);
    System.out.println(result.count());
    System.out.println(result.toArray());

**多条件查询**  
我们只需要对query对象做出处理即可

Criteria criteria = new Criteria(); criteria.orOperator(Criteria.where("classId").is("2"),Criteria.where("teacher").is("Mr.wang"));
    criteria.andOperator(Criteria.where("classId").is("2"));
    query.addCriteria(criteria);