找到一篇非常好用的查询（https://www.cnblogs.com/wslook/p/9275861.html
）
一、使用QueryByExampleExecutor
1. 继承MongoRepository
public interface StudentRepository extends MongoRepository
2. 代码实现
- 使用ExampleMatcher匹配器-----只支持字符串的模糊查询，其他类型是完全匹配
- Example封装实体类和匹配器
- 使用QueryByExampleExecutor接口中的findAll方法
public Page<Student> getListWithExample(StudentReqVO studentReqVO) {
Sort sort = Sort.by(Sort.Direction.DESC, "createTime");
Pageable pageable = PageRequest.of(studentReqVO.getPageNum(), studentReqVO.getPageSize(), sort);
Student student = new Student();
BeanUtils.copyProperties(studentReqVO, student);
//创建匹配器，即如何使用查询条件
ExampleMatcher matcher = ExampleMatcher.matching() //构建对象
.withStringMatcher(ExampleMatcher.StringMatcher.CONTAINING) //改变默认字符串匹配方式：模糊查询
.withIgnoreCase(true) //改变默认大小写忽略方式：忽略大小写
.withMatcher("name", ExampleMatcher.GenericPropertyMatchers.contains()) //采用“包含匹配”的方式查询
.withIgnorePaths("pageNum", "pageSize"); //忽略属性，不参与查询
//创建实例
Example<Student> example = Example.of(student, matcher);
Page<Student> students = studentRepository.findAll(example, pageable);
return students;
}
缺点：
- 不支持过滤条件分组。即不支持过滤条件用 or(或) 来连接，所有的过滤条件，都是简单一层的用 and(并且) 连接
- 不支持两个值的范围查询，如时间范围的查询
二、MongoTemplate结合Query
实现一：使用Criteria封装查询条件
public Page<Student> getListWithCriteria(StudentReqVO studentReqVO) {</pre>
Sort sort = Sort.by(Sort.Direction.DESC, "createTime");
Pageable pageable = PageRequest.of(studentReqVO.getPageNum(), studentReqVO.getPageSize(), sort);
Query query = new Query();
//动态拼接查询条件
if (!StringUtils.isEmpty(studentReqVO.getName())){
Pattern pattern = Pattern.compile("^.*" + studentReqVO.getName() + ".*$", Pattern.CASE_INSENSITIVE);
query.addCriteria(Criteria.where("name").regex(pattern));
}
if (studentReqVO.getSex() != null){
query.addCriteria(Criteria.where("sex").is(studentReqVO.getSex()));
}
if (studentReqVO.getCreateTime() != null){
query.addCriteria(Criteria.where("createTime").lte(studentReqVO.getCreateTime()));
}
//计算总数
long total = mongoTemplate.count(query, Student.class);
//查询结果集
List<Student> studentList = mongoTemplate.find(query.with(pageable), Student.class);
Page<Student> studentPage = new PageImpl(studentList, pageable, total);
return studentPage;
}
实现二：使用Example和Criteria封装查询条件
public Page<Student> getListWithExampleAndCriteria(StudentReqVO studentReqVO) {</pre>
Sort sort = Sort.by(Sort.Direction.DESC, "createTime");
Pageable pageable = PageRequest.of(studentReqVO.getPageNum(), studentReqVO.getPageSize(), sort);
Student student = new Student();
BeanUtils.copyProperties(studentReqVO, student);
//创建匹配器，即如何使用查询条件
ExampleMatcher matcher = ExampleMatcher.matching() //构建对象
.withStringMatcher(ExampleMatcher.StringMatcher.CONTAINING) //改变默认字符串匹配方式：模糊查询
.withIgnoreCase(true) //改变默认大小写忽略方式：忽略大小写
.withMatcher("name", ExampleMatcher.GenericPropertyMatchers.contains()) //标题采用“包含匹配”的方式查询
.withIgnorePaths("pageNum", "pageSize"); //忽略属性，不参与查询
//创建实例
Example<Student> example = Example.of(student, matcher);
Query query = new Query(Criteria.byExample(example));
if (studentReqVO.getCreateTime() != null){
query.addCriteria(Criteria.where("createTime").lte(studentReqVO.getCreateTime()));
}
//计算总数
long total = mongoTemplate.count(query, Student.class);
//查询结果集
List<Student> studentList = mongoTemplate.find(query.with(pageable), Student.class);
Page<Student> studentPage = new PageImpl(studentList, pageable, total);
return studentPage;
}
缺点：
- 不支持返回固定字段
三、MongoTemplate结合BasicQuery
- BasicQuery是Query的子类
- 支持返回固定字段
public Page<Student> getListWithBasicQuery(StudentReqVO studentReqVO) {
Sort sort = Sort.by(Sort.Direction.DESC, "createTime");
Pageable pageable = PageRequest.of(studentReqVO.getPageNum(), studentReqVO.getPageSize(), sort);
QueryBuilder queryBuilder = new QueryBuilder();
//动态拼接查询条件
if (!StringUtils.isEmpty(studentReqVO.getName())) {
Pattern pattern = Pattern.compile("^.*" + studentReqVO.getName() + ".*$", Pattern.CASE_INSENSITIVE);
queryBuilder.and("name").regex(pattern);
}
if (studentReqVO.getSex() != null) {
queryBuilder.and("sex").is(studentReqVO.getSex());
}
if (studentReqVO.getCreateTime() != null) {
queryBuilder.and("createTime").lessThanEquals(studentReqVO.getCreateTime());
}
Query query = new BasicQuery(queryBuilder.get().toString());
//计算总数
long total = mongoTemplate.count(query, Student.class);
//查询结果集条件
BasicDBObject fieldsObject = new BasicDBObject();
//id默认有值，可不指定
fieldsObject.append("id", 1) //1查询，返回数据中有值；0不查询，无值
.append("name", 1);
query = new BasicQuery(queryBuilder.get().toString(), fieldsObject.toJson());
//查询结果集
List<Student> studentList = mongoTemplate.find(query.with(pageable), Student.class);
Page<Student> studentPage = new PageImpl(studentList, pageable, total);
return studentPage;
}
四、MongoTemplate结合Aggregation
- 使用Aggregation聚合查询
- 支持返回固定字段
- 支持分组计算总数、求和、平均值、最大值、最小值等等
public Page<Student> getListWithAggregation(StudentReqVO studentReqVO) {
Sort sort = Sort.by(Sort.Direction.DESC, "createTime");
Pageable pageable = PageRequest.of(studentReqVO.getPageNum(), studentReqVO.getPageSize(), sort);
Integer pageNum = studentReqVO.getPageNum();
Integer pageSize = studentReqVO.getPageSize();
List<AggregationOperation> operations = new ArrayList<>();
if (!StringUtils.isEmpty(studentReqVO.getName())) {
Pattern pattern = Pattern.compile("^.*" + studentReqVO.getName() + ".*$", Pattern.CASE_INSENSITIVE);
Criteria criteria = Criteria.where("name").regex(pattern);
operations.add(Aggregation.match(criteria));
}
if (null != studentReqVO.getSex()) {
operations.add(Aggregation.match(Criteria.where("sex").is(studentReqVO.getSex())));
}
long totalCount = 0;
//获取满足添加的总页数
if (null != operations && operations.size() > 0) {
Aggregation aggregationCount = Aggregation.newAggregation(operations); //operations为空，会报错
AggregationResults<Student> resultsCount = mongoTemplate.aggregate(aggregationCount, "student", Student.class);
totalCount = resultsCount.getMappedResults().size();
} else {
List<Student> list = mongoTemplate.findAll(Student.class);
totalCount = list.size();
}
operations.add(Aggregation.skip((long) pageNum * pageSize));
operations.add(Aggregation.limit(pageSize));
operations.add(Aggregation.sort(Sort.Direction.DESC, "createTime"));
Aggregation aggregation = Aggregation.newAggregation(operations);
AggregationResults<Student> results = mongoTemplate.aggregate(aggregation, "student", Student.class);
//查询结果集
Page<Student> studentPage = new PageImpl(results.getMappedResults(), pageable, totalCount);
return studentPage;
}
