JAVA代码实现MongoDB动态条件之分页查询

一、使用QueryByExampleExecutor

1. 继承MongoRepository

public interface StudentRepository extends MongoRepository<Student, String> {
  
}

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) {
  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) {
  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;
}

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