用list完成分页+排序+条件查询

因为对Mybatis的拦截器了解不深，自己又想写一个类似pageHelper的分页插件，最后决定用很笨拙的方式实现分页+排序+条件查询的功能。

代码如下：

package com.l712.persistent.common;

import com.github.pagehelper.PageHelper;
import com.l712.pojo.common.PageBean;
import com.l712.pojo.common.PageQuery;
import com.l712.utils.common.CommonStringUtils;
import com.l712.utils.common.SpringUtils;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
import org.apache.ibatis.session.SqlSession;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.PropertySource;
import org.springframework.stereotype.Component;
import org.springframework.util.comparator.ComparableComparator;

import javax.validation.constraints.NotNull;
import java.lang.reflect.Method;
import java.util.*;
import java.util.concurrent.CopyOnWriteArrayList;

/**
 *
 * @author l12
 * @T 查询的Pojo
 */
@Component
@NoArgsConstructor
@Data
public class MyBatisSimplePage<T> {
    @Value("${method:list}")
    private String methodName;
    @NotNull
    private Method method;

    @SuppressWarnings("unchecked")
    public PageBean<T> pageList(Class mapper, Integer pageSize, Integer currentPage, PageQuery pageQuery) {
        PageBean<T> pageBean = new PageBean<T>();
        try {
            Object o = SpringUtils.getBean(mapper);
            method = mapper.getMethod(methodName);
            ArrayList<T> allResults = (ArrayList<T>)method.invoke(o);
            if(allResults != null && allResults.size()>0){
                setPageBean(pageSize, currentPage, pageBean, allResults);
                List<String> sorts = pageQuery.getSorts();
                if(sorts!=null && sorts.size()>0){
                    for (final String sort:sorts) {
                        Collections.sort(pageBean.getResults(), new Comparator<T>() {
                            @Override
                            public int compare(T t1, T t2) {
                                try {
                                    String o1 = t1.getClass().getDeclaredMethod("get"+ CommonStringUtils.toUpperFirstChar(sort)).invoke(t1)+"";
                                    String o2 = t2.getClass().getDeclaredMethod("get"+ CommonStringUtils.toUpperFirstChar(sort)).invoke(t2)+"";
                                    return o1.compareTo(o2);
                                } catch (Exception e) {
                                    e.printStackTrace();
                                }
                                return 0;
                            }
                        });
                    }
                }
            }
            return pageBean;
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
    }

    private void setPageBean(Integer pageSize, Integer currentPage, PageBean<T> pageBean, List<T> allResults) {
        pageBean.setPageSize(pageSize);
        pageBean.setCurrentPage(currentPage);
        pageBean.setTotalNum(allResults.size());
        pageBean.setTotalPage((pageBean.getTotalNum() + pageSize - 1) / pageSize);
        if(pageSize > allResults.size()){
            pageSize = allResults.size();
        }if(currentPage*pageSize > pageBean.getTotalNum()){
            pageBean.setResults(allResults.subList((currentPage-1)*pageSize,pageBean.getTotalNum()));
        }else{
            pageBean.setResults(allResults.subList((currentPage-1)*pageSize,currentPage*pageSize));
        }

    }

}

　　条件查询还没写，先睡个午觉，写完补充。TODO