new JSONObject()方法使返回的json格式数据的顺序与list集合中的数据顺序保持一致

原因在于json版本问题

json2.1以前源码中new JsonOjbect()中的构建函数是

 public JSONObject(){this.properties = new HashMap();}

而在2.3版本后源码为：

 public JSONObject(){this.properties = new ListOrderedMap();}

ListOrderedMap位于commons-collections的jar包里，与普通的map相比，ListOrderedMap的key可保持原有顺序，而hashmap是无序的

项目需求：

将mysql表中的所有字段名和字段注释，表名，表描述用json返回

表名和秒描述在一张表中展示e_move

 // 获取所有需要导出的表名public static String getTableInfoBeanJson() {JSONArray jsonarray = new JSONArray();Connection conn = DbHelper.getConnection();ResultSet rs = null;PreparedStatement ps = null;try {ps = DbHelper.getConnection().prepareStatement("select * from e_move");rs = ps.executeQuery();while (rs.next()) {JSONObject jsonobj = new JSONObject();String tableName = rs.getString("table_name");String tableDesc = rs.getString("desc");List<ColumnBean> colList = readTableColumn(conn, tableName);jsonobj.put("target", tableName);jsonobj.put("name", tableDesc);jsonobj.put("element", colList);jsonarray.add(jsonobj);}} catch (Exception e) {e.printStackTrace();} finally {DbHelper.Close(rs, ps, conn);}return jsonarray.toString();}//获取表中字段public static List<ColumnBean> readTableColumn(Connection conn, String tableName) {List<ColumnBean> colList = new ArrayList<ColumnBean>();ResultSet resultSet = null;try {DatabaseMetaData dbmd = conn.getMetaData();resultSet = dbmd.getTables(null, "%", "%", new String[] {"TABLE"});while (resultSet.next()) {String t1 = resultSet.getString("TABLE_NAME");ResultSet rs = dbmd.getColumns(null, "%", tableName, "%");if (t1.contains(tableName)) {while (rs.next()) {ColumnBean col = new ColumnBean();col.setName(rs.getString("REMARKS"));col.setEname(rs.getString("COLUMN_NAME"));colList.add(col);}}}} catch (Exception e) {e.printStackTrace();} finally {DbHelper.Close(resultSet, null, null);}return colList;}

ColumnBean.java

public class ColumnBean {private String ename; //字段名private String name; //注释public String getEname() {return ename;}public void setEname(String ename) {this.ename = ename;}public String getName() {return name;}public void setName(String name) {this.name = name;}}

注意：用json2.3版本后的，使用new JsonObject()则可以实现有序