二、Example 用法

 通用 easyjdbc 中的 Example 方法有两大类定义，一个参数，例如下面：
// EasyJdbcTemplate
List<T> findByExample(Example example);
 public Example example(Class<?> persistentClass);
//继承接口和实现类（EasyJdbcDao<泛型>,SimpleJdbcDao<泛型>）
注意： 从1.0.6及以上版本只需继承接口EasyJdbcDao<泛型>
Example example();

所有 Example 方法中的 example 类型都是 Object 类型，这是因为通用 easyjdbc 支持所有符合 Example 结构的参数，还有通用 easyjdbc 中提供的通用 Example

3.2 通用 Example

3.2.1 查询

示例：
Example example = new Example(User.class);
example.createCriteria().andGreaterThan("id", 100).andLessThan("id",151);
example.or().andLessThan("id", 41);
List<User> users = easyJdbcTemplate.findByExample(example);
// 使用链式 
Example example =easyJdbcTemplate.example(User.class);
example.createCriteria().andGreaterThan("id", 100).andLessThan("id",151);
example.andLessThan("id", 41);
example.list();

3.2.2 获取单列数据get

示例：
Example example = new Example(User.class);
example.createCriteria().andGreaterThan("id", 100).andLessThan("id",151);
example.or().andLessThan("id", 41);
User user= easyJdbcTemplate.getByExample(example);
// 使用链式
Example example =easyJdbcTemplate.example(User.class);
example.createCriteria().andGreaterThan("id", 100).andLessThan("id",151);
example.andLessThan("id", 41);
example.get();

3.2.3 获取总数 count

示例：
Example example = new Example(User.class);
example.createCriteria().andGreaterThan("id", 100).andLessThan("id",151);
example.or().andLessThan("id", 41);
int total = easyJdbcTemplate.countByExample(example);
// 使用链式
Example example =easyJdbcTemplate.example(User.class);
example.createCriteria().andGreaterThan("id", 100).andLessThan("id",151);
example.andLessThan("id", 41);
example.count();

3.2.4 动态 查询

示例：

Example example = new Example(User.class);
Example.Criteria criteria = example.createCriteria();
if(user.getUserName()!= null){
    criteria.andLike("userName", user.getUserName() + "%");
}
if(user.getId() != null){
    criteria.andGreaterThan("id", user.getId());
}
List<User> users =easyJdbcTemplate.findByExample(example);

3.2.5 排序

示例：

Example example = new Example(User.class);
//单字段排序
 Sorts sort=new Sorts(Sorts.Direction.DESC, "id");
//多字段排序
 Sorts.Order order=new Sorts.Order(Sorts.Direction.DESC, "id");;
 Sorts.Order order1=new Sorts.Order(Sorts.Direction.DESC, "createTime");;
        Sorts sort=new Sorts(order，order1);
        example.orderByClause(sort);
List<User> users = easyJdbcTemplate.findByExample(example);

3.2.6 去重

示例：

//设置 distinct
Example example = new Example(User.class)
example.isDistinct(true);
Example.Criteria criteria = example.createCriteria();
if(user.getUserName()!= null){
    criteria.andLike("userName", user.getUserName() + "%");
}
List<User> users = easyJdbcTemplate.findByExample(example);

3.2.7 动态映射对象

示例：

Example example=new Example(User.class);
Example.Criteria criteria = example.createCriteria();
if(user.getUserName()!= null){
    criteria.andLike("userName", user.getUserName() + "%");
}
  example.entityClass(UserDTO.class);
List<UserDTO> users = easyJdbcTemplate.findByExample(example);

3.2.8 mapping动态组装对象

示例：

Example example=new Example(User.class);
Example.Criteria criteria = example.createCriteria();
if(user.getUserName()!= null){
    criteria.andLike("userName", user.getUserName() + "%");
}
  example.mapping("id","userId"); //初始化映射数据库对象User（DO）字段id 动态映射组装UserDTO的字段为userId
  example.entityClass(UserDTO.class); //组装UserDTO(DTO)
List<UserDTO> users = easyJdbcTemplate.findByExample(example);

3.2.9 分组查询

示例：

Example example=new Example(User.class);
example.groupByClause("id");
Example.Criteria criteria = example.createCriteria();
if(user.getUserName()!= null){
    criteria.andLike("userName", user.getUserName() + "%");
}
List<User> users = easyJdbcTemplate.findByExample(example);

3.2.10 动态定义查询项

示例：

Example example=new Example(User.class);
example.selectPropertys（"id","userName"）；
Example.Criteria criteria = example.createCriteria();
if(user.getUserName()!= null){
    criteria.andLike("userName", user.getUserName() + "%");
}
List<User> users = easyJdbcTemplate.findByExample(example);

3.2.11 动态聚合函数查询

示例：

Example example=new Example(User.class);
//定义一个函数 
Aggregation aggregation=new Aggregation(AggregateType.MAX.toString(), "age", "maxAge");
//定义多函数
 List list=new ArrayList();
  Aggregation.Aggregate aggregate=new Aggregation.Aggregate(AggregateType.MAX.toString(), "age", "maxAge");
  Aggregation.Aggregate aggregate1=new Aggregation.Aggregate(AggregateType.SUM.toString(), "id", "sumId");
    list.add(aggregate,aggregate1)
   Aggregation aggregation=new Aggregation(list);
example.selectPropertys（Aggregation,"id"）；
Example.Criteria criteria = example.createCriteria();
if(user.getUserName()!= null){
    criteria.andLike("userName", user.getUserName() + "%");
}
 example.entityClass(UserDTO.class); //组装UserDTO(DTO)
List<UserDTO> users = easyJdbcTemplate.findByExample(example);

3.2.12 分页

示例：

Example example=new Example(User.class);
example.pageInfo(1,2);
Example.Criteria criteria = example.createCriteria();
if(user.getUserName()!= null){
    criteria.andLike("userName", user.getUserName() + "%");
}
  example.entityClass(UserDTO);
   PageInfo<UserDTO> pageInfo=easyJdbcTemplate.findByPage(example);
//使用链式
Example example =easyJdbcTemplate.example(User.class);
Example.Criteria criteria = example.createCriteria();
if(user.getUserName()!= null){
    criteria.andLike("userName", user.getUserName() + "%");
}
  example.entityClass(UserDTO .class);
PageInfo<UserDTO> pageInfo=example.page();

原文: https://github.com/xphsc/easyjdbc/wiki/3.2-Example