Java JDBC读取大文本类型数据（CLOB）

Java JDBC读取大文本类型数据（CLOB）

开发中我们常常要把一些大文本类型数据存入数据库，例如一片文章这是后我们就需要数据库的CLOB类型来存储了。

 

一、建立数据库表

此不省略，因个人业务需求来建立。

 

二、程序实现

 

1、建立Java JDBC 工具类

 

package com.haerbin.JDBCProject.Connection;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public final class JdbcUtil_Oracle
{
	private static String url = "jdbc:oracle:thin:@localhost:1521:orcl";
	private static String user = "scott";
	private static String password = "tigger";

	private JdbcUtil_Oracle()
	{
	}

	static
	{
		try
		{
			Class.forName("oracle.jdbc.driver.OracleDriver");
		}
		catch (ClassNotFoundException e)
		{
			throw new ExceptionInInitializerError(e);
		}
	}

	public static Connection getConnection() throws SQLException
	{
		return DriverManager.getConnection(url, user, password);
	}

	public static void free(ResultSet rs, Statement st, Connection conn)
	{
		try
		{
			if (rs != null)
				rs.close();
		}
		catch (SQLException e)
		{
			e.printStackTrace();
		}
		finally
		{
			try
			{
				if (st != null)
					st.close();
			}
			catch (SQLException e)
			{
				e.printStackTrace();
			}
			finally
			{
				if (conn != null)
					try
					{
						conn.close();
					}
					catch (SQLException e)
					{
						e.printStackTrace();
					}
			}
		}
	}
}

 

2、建立大文本类模型（DAOMAIN）

 

package com.haerbin.JDBCProject.Daomain;

public class Clob
{
	private int id;

	private Clob clob_text;

	public int getId()
	{
		return id;
	}

	public void setId(int id)
	{
		this.id = id;
	}

	public Clob getClob_text()
	{
		return clob_text;
	}

	public void setClob_text(Clob clob_text)
	{
		this.clob_text = clob_text;
	}
}

 

3、建立业务层接口

 

package com.haerbin.JDBCProject.Dao;

import java.io.File;
import java.io.IOException;
import java.io.Reader;

public interface ClobDao
{
	public void AddClob(Reader reader, File file) throws IOException;
	
	public void getClob(Reader reader, File file) throws IOException;
}

 

4、建立业务实现代码

 

package com.haerbin.JDBCProject.DaoImpl;

import java.io.BufferedWriter;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.io.Reader;
import java.io.Writer;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;

import com.haerbin.JDBCProject.Connection.JdbcUtil_Oracle;
import com.haerbin.JDBCProject.Dao.ClobDao;

public class ClobDaoImpl implements ClobDao
{
	/**
	 * 将clob类型数据存入数据库。
	 */

	public void AddClob(Reader reader, File file) throws IOException
	{
		Connection conn = null;
		PreparedStatement ps = null;
		ResultSet rs = null;

		try
		{
			conn = JdbcUtil_Oracle.getConnection();
			String sql = "insert into clobtable(id, clob_text) values(my_sequences.nextval, ?)";
			ps = conn.prepareStatement(sql);

			ps.setCharacterStream(1, reader, (int) file.length());

			ps.executeUpdate();
		}
		catch (Exception e)
		{
			e.printStackTrace();
		}
		finally
		{
			JdbcUtil_Oracle.free(rs, ps, conn);
			reader.close();
		}
	}

	/**
	 * 从数据库中取得clob类型数据
	 */
	public void getClob(Reader reader, File file) throws IOException
	{
		Connection conn = null;
		PreparedStatement ps = null;
		ResultSet rs = null;
		int i;// 用来装Reader读取的字符

		char[] buffer = new char[1024]; // Reader时候的缓冲区

		Writer writer = new BufferedWriter(new FileWriter(file));

		try
		{
			conn = JdbcUtil_Oracle.getConnection();
			String sql = "select clob_text from clobtable";
			ps = conn.prepareStatement(sql);

			rs = ps.executeQuery();

			while (rs.next())
			{
				reader = rs.getCharacterStream("clob_text");

				while ((i = reader.read(buffer)) != -1)
				{
					writer.write(buffer, 0, i);

					System.out.println(new String(buffer, 0, i));
				}
			}

		}
		catch (Exception e)
		{
			e.printStackTrace();
		}
		finally
		{
			JdbcUtil_Oracle.free(rs, ps, conn);
			reader.close();
			writer.close();
		}

	}

}

 

5、调用接口实现大文本对象的存入

 

package com.haerbin.JDBCProject.Beans;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.io.Reader;

import com.haerbin.JDBCProject.Dao.ClobDao;
import com.haerbin.JDBCProject.DaoImpl.ClobDaoImpl;

public class ClobTest
{

	/**
	 * 数据库中存入大文本类型 jdbc 存入大文本需要一个Reader , 通过 Reader reader = new
	 * BufferedReader(new FileReader(file)); 来实现， 传过去File的原因是 ，
	 * jdbc那个方法需要知道文本的长度， 用file.length()可以求出来。 jdbc存入大文本只能是纯文本的.
	 * 
	 * 
	 * @throws IOException
	 */
	public static void main(String[] args) throws IOException
	{
		/*存入clob类型数据*/
		ClobDao cd = new ClobDaoImpl();

		/*MYSQL 用汉字的时候不可以插入，  ORACLE可以  ，  这是因为数据库字符问题*/
		
		File file = new File("D:/clob.txt");

		Reader reader = new BufferedReader(new FileReader(file));

		cd.AddClob(reader, file);
		
		/*从数据库读取clob类型数据*/
//		ClobDao cd = new ClobDaoImpl();
//		
//		File file = new File("D:/clob.txt");
//		
//		Reader reader = new BufferedReader(new FileReader(file));
//		
//		cd.getClob(reader, file);

	}
}