java 组装树型结构数据

自己开发遇到的后台组装的树结构方法，记录下来

1、首先数据库为oracle，使用 start with 语句和union 组装要查询数据：

SELECT * from (
SELECT equip.EQUIP_CATEGORY_ID as ID,equip.EQUIP_CATEGORY_NAME as name,'' as PID,'1' as LEV FROM SYS_DIS_DEFECT_LIBRARY equip
UNION ALL
SELECT PARTS."ID" as id,PARTS.PARTS_NAME as name,PARTS.EQUIP_CATEGORY_ID as PID,'2' as LEV FROM SYS_DIS_DEFECT_PARTS parts
UNION ALL
SELECT PLACE.id as id,PLACE.PLACE_NAME as name,PLACE.PARTS_ID as pid,'3' as LEV from SYS_DIS_DEFECT_PLACE place
UNION ALL
SELECT DESCR."ID" as id,DESCR.DESCRIPTION as name,DESCR.PLACE_ID as pid,'4' as LEV from SYS_DIS_DEFECT_DESCRIPTION descr
UNION ALL
SELECT CLASSIF."ID" as id,CLASSIF.CLASSIFICATION as name,CLASSIF.DESCRIPTION_ID as pid,'5' as LEV from SYS_DIS_DEFECT_CLASSIFICATION classif
)t START WITH t.pid is null CONNECT by PRIOR t.id = t.pid ;

dao层实现方法

public List<Map<String, Object>> getDefectStandLibraryTree(String rootId) {
		List<Map<String, Object>> result = null;
		Map<String, Object> paramMap = new HashMap<String, Object>();
		paramMap.put("rootId", rootId);
		StringBuilder sql = new StringBuilder();
		sql.append("SELECT * from ( ");
		sql.append("SELECT equip.EQUIP_CATEGORY_ID as ID,equip.EQUIP_CATEGORY_NAME as name,'' as PID FROM SYS_DIS_DEFECT_LIBRARY equip ");
		sql.append("UNION ALL ");
		sql.append("SELECT PARTS.ID as id,PARTS.PARTS_NAME as name,PARTS.EQUIP_CATEGORY_ID as PID FROM SYS_DIS_DEFECT_PARTS parts ");
		sql.append("UNION ALL ");
		sql.append("SELECT PLACE.id as id,PLACE.PLACE_NAME as name,PLACE.PARTS_ID as pid from SYS_DIS_DEFECT_PLACE place ");
		sql.append("UNION ALL ");
		sql.append("SELECT DESCR.ID as id,DESCR.DESCRIPTION as name,DESCR.PLACE_ID as pid from SYS_DIS_DEFECT_DESCRIPTION descr ");
		sql.append("UNION ALL ");
		sql.append("SELECT CLASSIF.ID as id,CLASSIF.CLASSIFICATION as name,CLASSIF.DESCRIPTION_ID as pid from SYS_DIS_DEFECT_CLASSIFICATION classif ");
		if(SystemUtils.isEmpty(rootId)){
			sql.append(")t START WITH t.pid is null CONNECT by PRIOR t.id = t.pid ");
			result = sqlSupportDao.findBySQL(sql.toString());
		}else {
			paramMap.put("rootId", rootId);
			sql.append(")t START WITH t.pid =:rootId CONNECT by PRIOR t.id = t.pid ");
			result = sqlSupportDao.findBySQL(sql.toString(), paramMap);
		}
		return result;
	}

2、将list数据处理，组装成Tree数据结构

这里使用的迭代的算法

service层

public DslTreeBO getDefectStandLibraryTree(String rootId) {
		List<Map<String, Object>> result = sysDisDefectLibraryDao
				.getDefectStandLibraryTree(rootId);
		DslTreeBO treeRoot = new DslTreeBO("0", "缺陷标准库", "0");
		if(!SystemUtils.isEmpty(rootId)){
			treeRoot.setChildren(getChildren(result,rootId));
		}else{
			treeRoot.setChildren(getChildren(result,"null"));
		}
		return treeRoot;
	}

迭代方法

// 取节点的所有children
	private List<DslTreeBO> getChildren(List<Map<String, Object>> results, String rootId) {

		List<DslTreeBO> list = new ArrayList<DslTreeBO>();
		for (int i = 0; i < results.size(); i++) {
			Map<String, Object> objs = results.get(i);
			if (rootId.equals(objs.get("PID")+"")) {
				DslTreeBO root = new DslTreeBO(objs.get("ID")+"", objs.get("NAME")+"", objs.get("LEV")+"");
				List<DslTreeBO> children = getChildren(results.subList(i, results.size()),
						String.valueOf(objs.get("ID")));
				if (!children.isEmpty()) {
					root.setChildren(children);
				}
				list.add(root);
			}
		}
		return list;
	}

最后是TreeBo实体

public class DslTreeBO {
	private String id;
	private String name;
	private String level;
	List<DslTreeBO> children;
	//缺陷等级
	private String defectLevel;

	public String getDefectLevel() {
		return defectLevel;
	}
	public void setDefectLevel(String defectLevel) {
		this.defectLevel = defectLevel;
	}
	public String getId() {
		return id;
	}
	public void setId(String id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public String getLevel() {
		return level;
	}
	public void setLevel(String level) {
		this.level = level;
	}
	public List<DslTreeBO> getChildren() {
		/*if(this.children==null){
			return this.children= new LinkedList<DslTreeBO>();
		}else{
			return children;
		}*/
		if(this.children==null){
			return null;
		}else{
			return children;
		}
	}
	public void setChildren(List<DslTreeBO> children) {
		if(this.children==null){
			this.children= new LinkedList<DslTreeBO>();
		}
		this.children.addAll(children);
	}
	public DslTreeBO(String id, String name, String level) {
		super();
		this.id = id;
		this.name = name;
		this.level = level;
	}
	public DslTreeBO(String id, String name, String level,String defectLevel) {
		super();
		this.defectLevel = defectLevel;
		this.id = id;
		this.name = name;
		this.level = level;
	}
	public DslTreeBO() {
		super();
		// TODO Auto-generated constructor stub
	}

}