list转map,list转tree,减少数据库查询次数

package com.oceano.utils;

import java.util.List;

public class TreeModel<K> {
    private K node;
    private List<TreeModel<K>> treeList;

    public K getNode() {
	return node;
    }

    public void setNode(K node) {
	this.node = node;
    }

    public List<TreeModel<K>> getTreeList() {
	return treeList;
    }

    public void setTreeList(List<TreeModel<K>> treeList) {
	this.treeList = treeList;
    }

    @Override
    public String toString() {
	return "TreeModel [node=" + node + ", treeList=" + treeList + "]";
    }

    public TreeModel(K node, List<TreeModel<K>> treeList) {
	super();
	this.node = node;
	this.treeList = treeList;
    }

    public TreeModel() {
	super();
	// TODO Auto-generated constructor stub
    }

}

package com.oceano.utils;

import java.lang.reflect.InvocationTargetException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.apache.commons.beanutils.PropertyUtils;

public class ListToMapUtil {

	@SuppressWarnings("unchecked")
	public static <T, K> Map<K, List<T>> listToMap(String fieldName, List<T> list) {
		if (null == fieldName) {
			throw new IllegalArgumentException("fieldName is null");
		}
		if (null == list) {
			throw new IllegalArgumentException("list is null");
		}

		Map<K, List<T>> map = new HashMap<>();

		for (T t : list) {
			K key = null;
			try {
				key = (K) PropertyUtils.getProperty(t, fieldName);
			} catch (IllegalAccessException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			} catch (InvocationTargetException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			} catch (NoSuchMethodException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}

			if (null == key) {
				throw new IllegalArgumentException("key is null");
			}

			if (null == map.get(key)) {
				List<T> tList = new ArrayList<>();
				tList.add(t);
				map.put(key, tList);
			} else {
				List<T> tList = map.get(key);
				tList.add(t);
			}
		}

		return map;
	}

}

package com.oceano.utils;

import java.lang.reflect.InvocationTargetException;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;

import org.apache.commons.beanutils.PropertyUtils;

public class ListToTreeUtils {

    public static <K, T> List<TreeModel<K>> listToTree(List<K> kList, T parentId, String parentFieldName,
	    String childFieldName) {

	Map<T, List<K>> map = ListToMapUtil.listToMap(parentFieldName, kList);

	List<TreeModel<K>> treeModelListReturn = new ArrayList<>();

	List<K> listTemp = map.get(parentId);

	treeModelListReturn = listToTreeFor(listTemp, childFieldName, map);

	return treeModelListReturn;

    }

    @SuppressWarnings({ "rawtypes", "unchecked" })
    private static <K, T> List<TreeModel<K>> listToTreeFor(List<K> kList, String childFieldName, Map<T, List<K>> map) {
	List<TreeModel<K>> treeModelListReturn = new ArrayList<>();
	for (K k : kList) {
	    TreeModel treeModel = new TreeModel();
	    treeModel.setNode(k);

	    String key;
	    try {
		key = (String) PropertyUtils.getProperty(k, childFieldName);
		List<K> listTemp2 = map.get(key);
		if (listTemp2 != null) {
		    List<TreeModel<K>> childrenList = listToTreeFor(listTemp2, childFieldName, map);
		    treeModel.setTreeList(childrenList);
		}
		treeModelListReturn.add(treeModel);
		
	    } catch (IllegalAccessException e) {
		// TODO Auto-generated catch block
		e.printStackTrace();
	    } catch (InvocationTargetException e) {
		// TODO Auto-generated catch block
		e.printStackTrace();
	    } catch (NoSuchMethodException e) {
		// TODO Auto-generated catch block
		e.printStackTrace();
	    }

	}
	return treeModelListReturn;

    }

}

package com.oceano.utils;

import java.util.ArrayList;
import java.util.List;

import com.oceano.modity.entity.T_Category;
import com.oceano.modity.vo.api.SieveConditionVo;

public class TreeModelToSieveConditionVoListUtils {

    public static List<SieveConditionVo> treeModelToSieveConditionVoList(
	    List<TreeModel<T_Category>> categoryTreeModelList) {

	List<SieveConditionVo> sieveConditionVoList = treeModelToSieveConditionVoListFor(categoryTreeModelList);

	return sieveConditionVoList;

    }

    private static List<SieveConditionVo> treeModelToSieveConditionVoListFor(
	    List<TreeModel<T_Category>> categoryTreeModelList) {
	List<SieveConditionVo> sieveConditionVoList = new ArrayList<>();

	for (TreeModel<T_Category> treeModel : categoryTreeModelList) {
	    T_Category category = treeModel.getNode();

	    SieveConditionVo sieveConditionVo = new SieveConditionVo();
	    sieveConditionVo.setId(category.getId());
	    sieveConditionVo.setCode(category.getCateCode());
	    sieveConditionVo.setName(category.getCateName());
	    sieveConditionVo.setParentId(category.getParentId());

	    List<TreeModel<T_Category>> treeModelList = treeModel.getTreeList();
	    if (treeModelList != null && treeModelList.size() > 0) {
		List<SieveConditionVo> childrenSieveConditionVoList = treeModelToSieveConditionVoListFor(treeModelList);
		sieveConditionVo.setChildren(childrenSieveConditionVoList);
	    }
	    sieveConditionVoList.add(sieveConditionVo);
	}

	return sieveConditionVoList;

    }

}