从java中的对象表中检索结构类型

Posted 2023-03-28

【中文标题】从java中的对象表中检索结构类型

【英文标题】：Retrieve struct type from a object table in java

【发布时间】：2013-06-24 13:59:12

【问题描述】：

你好，我需要从 oracle 对象表（地址）中获取值，为此我想用 oracle 类型（地址）映射一个 java 类（地址）。从 Jframe 中的按钮我可以打印 al 数据。所以：

Sql：

create or replace type address_t as object( no varchar2(7), str varchar2(40), city varchar2(25), country varchar2(25) );

create table airp (id_pk number(5),
location address_t);

Java 地址类：

import test.Test;
import java.sql.Connection;
import java.sql.SQLData;
import java.sql.SQLException;
import java.sql.SQLInput;
import java.sql.SQLOutput;
import java.util.logging.Level;
import java.util.logging.Logger;


public class Address implements SQLData 
  private String str;
  private String no;
  private String city;
  private String country;
  private String sql_type;
  private Connection conn = null;

  public Address()

  

  public Address(String sql_type, String no, String str, String city , String country)
      this.sql_type = sql_type;
      this.no = no;
      this.str = str;
      this.city = city;
      this.country = country;  

  

    @Override
    public String getSQLTypeName() throws SQLException 
        return this.sql_type;
    

    @Override
    public void readSQL(SQLInput stream, String typeName) throws SQLException 
        this.sql_type = typeName;
        no = stream.readString();
        str = stream.readString();
        city = stream.readString();
        country = stream.readString();

    

    @Override
    public void writeSQL(SQLOutput stream) throws SQLException 
        stream.writeString(no);
        stream.writeString(str);
        stream.writeString(city);
        stream.writeString(country);

    

    @Override
    public String toString()
        return sql_type+" "+no+" "+" "+city+" "+country;

    

还有按钮：

private void jButton1ActionPerformed(java.awt.event.ActionEvent evt)                                          

                try 

                    java.util.Map map = con.getTypeMap();
                    map.put("LI.ADDRESS_T", Class.forName("test.Address"));
                    con.setTypeMap((Map)map);
                    map = con.getTypeMap();

                    sql = "select * from aerop";
                    st = (OracleStatement)con.createStatement();
                    rs = (OracleResultSet)st.executeQuery(sql);

                    while(rs.next())
                        System.out.println(rs.getObject(1));
                    
                 catch (SQLException ex) 
                    Logger.getLogger(Test.class.getName()).log(Level.SEVERE, null, ex);
                 catch (ClassNotFoundException ex) 

                    Logger.getLogger(Test.class.getName()).log(Level.SEVERE, null, ex);
                

我得到下一个错误

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at test.Test.jButton1ActionPerformed

【参考方案1】：

con 或 con.getTypeMap() 是 null。为什么不调试呢？

【讨论】：

什么？你是在讽刺还是你真的是认真的？ :)

我已经在那个东西上工作了将近 2 个小时，因为我已经声明了连接但我忘了创建它，新手错误