经过我的一番研究：
public void test() {
/*OOO类就是Model类*/
Field[] fields = OOO.class.getDeclaredFields();
List<Projection> projections = new ArrayList<>();
for(int i = 0; i < fields.length; i ++) {
if(Modifier.isStatic(fields[i].getModifiers())) {/*去除静态变量*/
continue;
}
projections.add(Projection.projection(fields[i].getName()));
}
/*虚拟字段A的值来源于X字段与O字段之和*/
projections.add(Projection.projection("A", Projection.add("$X", "$O")));
AggregationPipeline pip = miDao.createAggregation()
.project(projections.toArray(new Projection[projections.size()]));"$peerNominateCount")))
.sort(Sort.descending("A"));
Iterator<XXX> list = pip.aggregate(XXX.class);
while(list.hasNext()) {
System.out.println(list.next().toString());
}
}
/*XXX是专门为查询出的新数据设计的数据结构，当然你也可以把OOO类中的字段添加过来，或者直接继承它*/
private static class XXX{
private static class TestModel{
@Id
private ObjectId id;
private Long A;
public ObjectId getId() {
return id;
}
public void setId(ObjectId id) {
this.id = id;
}
public Long getA() {
return A;
}
public void setA(Long A) {
this.A = A;
}
@Override
public String toString() {
return "TestModel [id=" + id + ", A=" + A + "]";
}
}
}
