JAVA如何實現MongoDB動態條件的分頁查詢

發布時間：2020-07-16 13:35:48 來源：億速云閱讀：1013 作者：小豬欄目：開發技術

這篇文章主要講解了JAVA如何實現MongoDB動態條件的分頁查詢，內容清晰明了，對此有興趣的小伙伴可以學習一下，相信大家閱讀完之后會有幫助。

一、使用QueryByExampleExecutor

1. 繼承MongoRepository

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

2. 代碼實現

使用ExampleMatcher匹配器-----只支持字符串的模糊查詢，其他類型是完全匹配
Example封裝實體類和匹配器
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);

  //創建匹配器，即如何使用查詢條件
  ExampleMatcher matcher = ExampleMatcher.matching() //構建對象
      .withStringMatcher(ExampleMatcher.StringMatcher.CONTAINING) //改變默認字符串匹配方式：模糊查詢
      .withIgnoreCase(true) //改變默認大小寫忽略方式：忽略大小寫
      .withMatcher("name", ExampleMatcher.GenericPropertyMatchers.contains()) //采用“包含匹配”的方式查詢
      .withIgnorePaths("pageNum", "pageSize"); //忽略屬性，不參與查詢

  //創建實例
  Example<Student> example = Example.of(student, matcher);
  Page<Student> students = studentRepository.findAll(example, pageable);

  return students;
}

缺點：

不支持過濾條件分組。即不支持過濾條件用 or(或) 來連接，所有的過濾條件，都是簡單一層的用 and(并且) 連接
不支持兩個值的范圍查詢，如時間范圍的查詢

二、MongoTemplate結合Query

實現一：使用Criteria封裝查詢條件

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();

  //動態拼接查詢條件
  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()));
  }

  //計算總數
  long total = mongoTemplate.count(query, Student.class);

  //查詢結果集
  List<Student> studentList = mongoTemplate.find(query.with(pageable), Student.class);
  Page<Student> studentPage = new PageImpl(studentList, pageable, total);
  return studentPage;
}

實現二：使用Example和Criteria封裝查詢條件

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);

  //創建匹配器，即如何使用查詢條件
  ExampleMatcher matcher = ExampleMatcher.matching() //構建對象
      .withStringMatcher(ExampleMatcher.StringMatcher.CONTAINING) //改變默認字符串匹配方式：模糊查詢
      .withIgnoreCase(true) //改變默認大小寫忽略方式：忽略大小寫
      .withMatcher("name", ExampleMatcher.GenericPropertyMatchers.contains()) //標題采用“包含匹配”的方式查詢
      .withIgnorePaths("pageNum", "pageSize"); //忽略屬性，不參與查詢

  //創建實例
  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()));
  }

  //計算總數
  long total = mongoTemplate.count(query, Student.class);

  //查詢結果集
  List<Student> studentList = mongoTemplate.find(query.with(pageable), Student.class);
  Page<Student> studentPage = new PageImpl(studentList, pageable, total);
  return studentPage;
}

缺點：

不支持返回固定字段

三、MongoTemplate結合BasicQuery

BasicQuery是Query的子類
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();

  //動態拼接查詢條件
  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());
  //計算總數
  long total = mongoTemplate.count(query, Student.class);

  //查詢結果集條件
  BasicDBObject fieldsObject = new BasicDBObject();
  //id默認有值，可不指定
  fieldsObject.append("id", 1)  //1查詢，返回數據中有值；0不查詢，無值
        .append("name", 1);
  query = new BasicQuery(queryBuilder.get().toString(), fieldsObject.toJson());

  //查詢結果集
  List<Student> studentList = mongoTemplate.find(query.with(pageable), Student.class);
  Page<Student> studentPage = new PageImpl(studentList, pageable, total);
  return studentPage;
}

四、MongoTemplate結合Aggregation

使用Aggregation聚合查詢
支持返回固定字段
支持分組計算總數、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;
  //獲取滿足添加的總頁數
  if (null != operations && operations.size() > 0) {
    Aggregation aggregationCount = Aggregation.newAggregation(operations); //operations為空，會報錯
    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);

  //查詢結果集
  Page<Student> studentPage = new PageImpl(results.getMappedResults(), pageable, totalCount);
  return studentPage;
}

看完上述內容，是不是對JAVA如何實現MongoDB動態條件的分頁查詢有進一步的了解，如果還想學習更多內容，歡迎關注億速云行業資訊頻道。

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