mongo page query based on conditions

一、MongoTemplate 中 Aggregation 应用

• 使用Aggregation聚合查询
• 支持返回固定字段
• 支持分组计算（count）总数、(sum)求和、(avg)平均值、(max)最大值、(min)最小值等

public Page<Student> getListWithAggregation(StudentVO studentVO) {
    Sort sort = Sort.by(Sort.Direction.DESC, "createTime"); 
    Pageable pageable = PageRequest.of(studentVO.getPageNum(), studentVO.getPageSize(), sort);
    Integer pageNum = studentVO.getPageNum();
    Integer pageSize = studentVO.getPageSize();
    List<AggregationOperation> operations = new ArrayList<>();   
    if (!StringUtils.isEmpty(studentVO.getName())) {       
           Pattern pattern = Pattern.compile("^.*" + studentVO.getName() + ".*$", Pattern.CASE_INSENSITIVE);       
           Criteria criteria = Criteria.where("name").regex(pattern);
           operations.add(Aggregation.match(criteria));    }    
          if (null != studentVO.getSex()) {
               operations.add(Aggregation.match(Criteria.where("sex").is(studentVO.getSex())));
          }    

          //获取满足添加的总页数 

　　　　　　long totalCount = 0; if (null != operations && operations.size() > 0) {
　　　　　　　   Aggregation aggregationCount = Aggregation.newAggregation(operations);
               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); 
          Page<Student> studentPage = new PageImpl(results.getMappedResults(), pageable, totalCount);
    return studentPage;
} 

二、MongoTemplate 结合 BasicQuery 的集合应用

public Page<Student> getListWithBasicQuery(StudentVO studentVO) {
    // 排序
    Sort sort = Sort.by(Sort.Direction.DESC, "createTime");
    Pageable pageable = PageRequest.of(studentVO.getPageNum(), studentVO.getPageSize(), sort);
    QueryBuilder queryBuilder = new QueryBuilder(); 
    if (!StringUtils.isEmpty(studentVO.getName())) {
        // 模糊查询
        Pattern pattern = Pattern.compile("^.*" + studentVO.getName() + ".*$", Pattern.CASE_INSENSITIVE); 
       queryBuilder.and("name").regex(pattern);
    }
    if (studentVO.getSex() != null) {
        queryBuilder.and("sex").is(studentVO.getSex());
    }
    if (studentVO.getCreateTime() != null) {
        queryBuilder.and("createTime").lessThanEquals(studentVO.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();

    fieldsObject.append("id", 1).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;
}

三、MongoTemplate结合Example和Criteria 的集合查询应用

public Page<Student> getListWithExampleAndCriteria(StudentVO studentVO) {
    Sort sort = Sort.by(Sort.Direction.DESC, "createTime");
    Pageable pageable = PageRequest.of(studentVO.getPageNum(), studentVO.getPageSize(), sort);
    Student student = new Student();
    BeanUtils.copyProperties(studentVO, 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 (studentVO.getCreateTime() != null){
        query.addCriteria(Criteria.where("createTime").lte(studentVO.getCreateTime()));
    }
    //计算总数
    long total = mongoTemplate.count(query, Student.class);
    //查询结果
    List<Student> studentList = mongoTemplate.find(query.with(pageable), Student.class);
    Page<Student> stuPageList = new PageImpl(studentList, pageable, total);
    return stuPageList;
}

四、MongoTemplate结合Query 的集合查询应用

public Page<Student> getListWithCriteria(StudentVO studentVO) {
    Sort sort = Sort.by(Sort.Direction.DESC, "createTime");
    Pageable pageable = PageRequest.of(studentVO.getPageNum(), studentVO.getPageSize(), sort);
    Query query = new Query();
    if (!StringUtils.isEmpty(studentVO.getName())){
        Pattern pattern = Pattern.compile("^.*" + studentVO.getName() + ".*$", Pattern.CASE_INSENSITIVE);
        query.addCriteria(Criteria.where("name").regex(pattern));
    }
    if (studentVO.getSex() != null){
        query.addCriteria(Criteria.where("sex").is(studentVO.getSex()));
    }
    if (studentVO.getCreateTime() != null){
        query.addCriteria(Criteria.where("createTime").lte(studentVO.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> stuPageList = new PageImpl(studentList, pageable, total);
    return stuPageList;
}

五、MongoTemplate结合 ExampleMatcher 的集合查询应用

• 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ExampleExecutor 接口中的findAll方法

public Page<Student> getListWithExample(StudentVO studentVO) {
    Sort sort = Sort.by(Sort.Direction.DESC, "createTime");
    Pageable pageable = PageRequest.of(studentVO.getPageNum(), studentVO.getPageSize(), sort);
    Student student = new Student();
    BeanUtils.copyProperties(studentVO, 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;
}