开心一夏

• 【核心语句】

  DatabaseMetaData metaData = conn.getMetaData();
  ResultSet rs= metaData.getColumns(null, null, tablename+"%", null);

• 重点是第二句的第三参数，如果置空就不分表了，那不是我们想看到的，于是将表名加上通配符%限制一下表的范围，再这样限制表：

  while (rs.next()) {
          String tbName = rs.getString("TABLE_NAME"); // 表名
  
          if(tbName.equalsIgnoreCase(tablename)){
                  String columnName = rs.getString("COLUMN_NAME"); // 列名
                  ls.add(columnName);
          }
  }

• 当取得rs的TABLE_NAME字段后，再限制一次，这下出现的字段就只会是指定表下的了。
• 【代码】

  package com.txc.lab;
  
  import java.sql.Connection;
  import java.sql.DatabaseMetaData;
  import java.sql.DriverManager;
  import java.sql.ResultSet;
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.List;
  
  /**
   * 此类用于查出某表下的所有字段名称
   */
  public class FieldFinder {
      //-- 以下为连接Oracle数据库的四大参数
      private static final String DRIVER = "oracle.jdbc.driver.OracleDriver";
      private static final String URL = "jdbc:oracle:thin:@127.0.0.1:1521:orcl";
      private static final String USER = "luna";
      private static final String PSWD = "1234";
  
      public void printFields(String tablename){
          Connection conn = null;
  
          try{
              Class.forName(DRIVER);
              conn = DriverManager.getConnection(URL, USER, PSWD);
  
              List<String> ls=getFields(conn,tablename);
              Collections.sort(ls);
              ls.stream().forEach(table -> System.out.println(table));
          } catch (Exception e) {
              e.printStackTrace();
          } finally {
              try {
                  conn.close();
              } catch (Exception e) {
                  e.printStackTrace();
              }
          }
      }
  
      private List<String> getFields(Connection conn,String tablename) throws Exception{
          DatabaseMetaData metaData = conn.getMetaData();
          ResultSet rs = metaData.getColumns(null, null, tablename+"%", null);
          List<String> ls=new ArrayList<>();
  
          while (rs.next()) {
              String tbName = rs.getString("TABLE_NAME"); // 表名
  
              if(tbName.equalsIgnoreCase(tablename)){
                  String columnName = rs.getString("COLUMN_NAME"); // 列名
                  ls.add(columnName);
              }
          }
          return ls;
      }
  
      public static void main(String[] args){
          FieldFinder finder=new FieldFinder();
          finder.printFields("EMP");
      }
  }

• 【参考资料】

https://blog.csdn.net/github_34793283/article/details/114109394