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;
}

来源：https://www.cnblogs.com/wslook/p/9275861.html