Spring Data JPA 动态拼接条件的通用设计模式

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import java.sql.Timestamp;
import java.util.ArrayList;
import java.util.List;
import javax.persistence.criteria.CriteriaBuilder;
import javax.persistence.criteria.CriteriaQuery;
import javax.persistence.criteria.Predicate;
import javax.persistence.criteria.Root;
import org.springframework.data.jpa.domain.Specification;
import com.xxx.controller.logManage.LogSearchParamDTO;
import com.xxx.controller.trade.TradeParams;
/**
 * 改进方向 1：能不能 通过反射 ，只要---
 * 相关知识请自行查阅JPA Criteria查询
// 过滤条件
// 1：过滤条件会被应用到SQL语句的FROM子句中。在criteria
// 查询中，查询条件通过Predicate或Expression实例应用到CriteriaQuery对象上。
// 2：这些条件使用 CriteriaQuery .where 方法应用到CriteriaQuery 对象上
// 3：CriteriaBuilder也作为Predicate实例的工厂，通过调用CriteriaBuilder 的条件方法（
// equal，notEqual， gt， ge，lt， le，between，like等）创建Predicate对象。
// 4：复合的Predicate 语句可以使用CriteriaBuilder的and, or andnot 方法构建。
 * @author 小言
 * @date 2017年11月27日
 * @time 上午10:44:53
 * @version ╮(╯▽╰)╭
 */
public class SpecificationBuilderForOperateLog {

    public static  Specification buildSpecification(Class clazz,
            final LogSearchParamDTO logSearchParamDTO) {
        return new Specification() {
            @Override
            public Predicate toPredicate(Root root, CriteriaQuery query, CriteriaBuilder cb) {
                List predicate = new ArrayList();
                Timestamp startTime = logSearchParamDTO.getStartTime();
                Timestamp endTime = logSearchParamDTO.getEndTime();
                // 时间段
                if (startTime != null && endTime != null) {
                    predicate.add(cb.between(root. get("logTime"), startTime, endTime));
                }
                // 操作日志查询栏
                String searchCondition = logSearchParamDTO.getSearchCondition();
                if (searchCondition != null && !searchCondition.equals("")) {
                    predicate.add(cb.or(cb.equal(root. get("operatorName"), searchCondition),
                            cb.equal(root. get("operatorId"), searchCondition)));
                }
                // 操作日志用户类型
                String operatorType = logSearchParamDTO.getOperatorType();
                System.out.println("operatorType=="+operatorType);
                if (operatorType != null ){
                    predicate.add(cb.equal(root. get("operatorType"), operatorType));
                }
                Predicate[] pre = new Predicate[predicate.size()];
//              System.out.println("pre=="+predicate.toArray(pre));
                query.where(predicate.toArray(pre));
                return query.getRestriction();
            }
        };
    }
}

下面是实际开发例子
controller层

@Controller
@RequestMapping(value = "/operateLog")
public class BgOperateLogController {

    @Autowired
    private BgOperateLogService bgOperateLogService;

    @ResponseBody
    @PostMapping("/findOperateLogByCondition")
    public Result findOperateLogByCondition(@RequestBody LogSearchParamDTO logSearchParamDTO) {
        System.out.println("logSearchParamDTO="+logSearchParamDTO);
        Map result = new HashMap<>();
        String start = logSearchParamDTO.getStart();
        String end = logSearchParamDTO.getEnd();
        if (start != null && end == null) {
            return new Result(1001, "操作日志查询错误,时间参数缺少结束时间", result);
        }
        if (end != null && start == null) {
            return new Result(1001, "操作日志查询错误,时间参数缺少开始时间", result);
        }
        //时间
        long startTimeTimestamp  = 0L;
        long endTimeTimestamp = System.currentTimeMillis();
        if(start != null && end != null){
            SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
            Date startTime;
            Date endTime;
            try {
                startTime = sdf.parse(start);
                endTime = sdf.parse(end);
                startTimeTimestamp = startTime.getTime();
                endTimeTimestamp = endTime.getTime();
            } catch (ParseException e) {
                e.printStackTrace();
                return new Result(1001, "操作日志查询错误，转换日期出错", result);
            }
        }
        String condition = logSearchParamDTO.getSearchCondition();
        Integer pageNumber = logSearchParamDTO.getPageNumber()-1;
        Integer pageSize = logSearchParamDTO.getPageSize() ;
        String operatorType =logSearchParamDTO.getOperatorType(); 
        Page findByCondition = bgOperateLogService.findByCondition(new Timestamp(startTimeTimestamp), 
                new Timestamp(endTimeTimestamp),
                condition,operatorType, pageNumber, pageSize);
        // 这些字段必须有，暂时没有做校验
        List list = findByCondition.getContent();
        result.put("totalPages", findByCondition.getTotalPages());
        result.put("pageNumber", pageNumber+1);
        result.put("list", list);
        return new Result(1002, "操作日志查询成功", result);
    }

}

DTO

@Data
public class LogSearchParamDTO {
    //前端传来的时间参数
    private String start;
    private String end;
    private Timestamp startTime;
    private Timestamp endTime;
    private String    searchCondition;
    //操作日志查询参数   
    //操作用户类型(0，消费者，1商家，2后台人员)
    private String operatorType;
    private Integer pageNumber;
    private Integer pageSize;
    //登陆日志查询条件
    public LogSearchParamDTO(Timestamp startTime, Timestamp endTime, String searchCondition) {
        this.startTime = startTime;
        this.endTime = endTime;
        this.searchCondition = searchCondition;
    }
    public LogSearchParamDTO() {}
    //操作日志查询条件
    public LogSearchParamDTO(Timestamp startTime, Timestamp endTime, String searchCondition, String operatorType) {
        this.startTime = startTime;
        this.endTime = endTime;
        this.searchCondition = searchCondition;
        this.operatorType = operatorType;
    }
}

service 层

@Override
    public Page findByCondition(Timestamp start, 
            Timestamp end, String condition ,String operatorType,
            int pageNumber, int pageSize) {
        Sort sort = new Sort(Sort.Direction.DESC, "logTime");
        Pageable pageable = new PageRequest(pageNumber, pageSize, sort);
        LogSearchParamDTO operateLog = new LogSearchParamDTO(start, end, condition,operatorType);
        Page page = bgOperateLogDao
                .findAll(SpecificationBuilderForOperateLog.buildSpecification(BgOperateLog.class,operateLog), pageable);
        return page;
    }

dao层

import java.io.Serializable;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.JpaSpecificationExecutor;
import org.springframework.stereotype.Repository;
import com.xxx.entity.BgOperateLog;
@Repository
public interface BgOperateLogDao extends JpaRepository,JpaSpecificationExecutor{}

entity层

@Data
@Entity
public class BgOperateLog implements java.io.Serializable {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Integer id;
    private String logText;
    private String operatorId;
    private String operatorName;
    private String operatorType;
    private String ip;
    @JsonFormat(pattern = "yyyy-MM-dd HH:mm:ss",timezone="GMT+8")
    private Timestamp logTime;
}