JDBC之大段文本数据的保存与读取

1、创建数据库测试表

DROP TABLE IF EXISTS `clob_test`;
CREATE TABLE `clob_test` (
  `id` int(10) NOT NULL AUTO_INCREMENT,
  `big_text` text COMMENT '大文本',
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=utf8;

2、JdbcUtils.java中的代码

package cn.itcast.jdbc;

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

/**
 * Jdbc工具类
 */
public final class JdbcUtils {
	
	//省略localhost:3306
	private static String url = "jdbc:mysql:///jdbc";
	private static String username = "root";
	private static String password = "root";
	
	/**
	 * 构造器私用,防止直接创建对象,
	 * 当然通过反射可以创建
	 */
	private JdbcUtils(){
		
	}
	
	//保证只是注册一次驱动
	static{
		try {
			Class.forName("com.mysql.jdbc.Driver");
		} catch (ClassNotFoundException e) {
			throw new ExceptionInInitializerError(e);
		}
	}
	
	/**
	 * 获取连接
	 * @return
	 * @throws SQLException
	 */
	public static Connection getConnection() throws SQLException {
		return DriverManager.getConnection(url, username, password);
	}
	
	/**
	 * 释放资源
	 */
	public static void free(ResultSet rs, Statement st, Connection conn) {
		//规范的关系连接的方式
		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();
					}
				}
			}
		}
	}
}

3、测试类中的代码

package cn.itcast.jdbc;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.Reader;
import java.io.Writer;
import java.sql.Clob;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

import org.junit.Test;

/**
 * JDBC之大段文本测试
 */
public class ClobTest {
	
	/**
	 * 测试创建
	 * @throws SQLException
	 * @throws IOException
	 */
	@Test
	public void testCreate() throws SQLException, IOException {
		create();
	}
	
	/**
	 * 测试读取
	 * @throws SQLException
	 * @throws IOException
	 */
	@Test
	public void testRead() throws SQLException, IOException {
		read();
	}
	
	/**
	 * 从数据库查询数据
	 * @throws SQLException
	 * @throws IOException
	 */
	static void read() throws SQLException, IOException {
		Connection conn = null;
		Statement st = null;
		ResultSet rs = null;
		
		try {
			//建立连接
			conn = JdbcUtils.getConnection();
			//创建语句
			st = conn.createStatement();
			//执行语句
			rs = st.executeQuery("select big_text from clob_test");
			//处理结果
			while(rs.next()) {
				Clob clob = rs.getClob("big_text");
				//获取字符流,这种方式可以
				//Reader reader = clob.getCharacterStream();
				//这种方式也可以
				Reader render = rs.getCharacterStream("big_text");
				String s = rs.getString("big_text");
				
				System.out.println(s);
				
				File file = new File("JdbcUtils_bak.java");
				Writer writer = new BufferedWriter(new FileWriter(file));
				char[] buff = new char[1024];
				int i = 0;
				while((i = render.read(buff)) > 0) {
					writer.write(buff, 0, i);
				}
				writer.close();
				render.close();
			}
		} finally {
			JdbcUtils.free(rs, st, conn);
		}
	}
	
	/**
	 * 从文本文件读取数据存入数据库
	 * @throws SQLException
	 * @throws IOException
	 */
	static void create() throws SQLException, IOException {
		Connection conn = null;
		PreparedStatement ps = null;
		ResultSet rs = null;
		
		try{
			//建立连接
			conn = JdbcUtils.getConnection();
			//创建语句
			String sql = "insert into clob_test(big_text) values(?)";
			ps = conn.prepareStatement(sql);
			File file = new File("src/cn/itcast/jdbc/JdbcUtils.java");
			//创建字符流,读取文件
			Reader reader = new BufferedReader(new FileReader(file));
			
			ps.setCharacterStream(1, reader, file.length());
			//执行语句
			int i = ps.executeUpdate();
			reader.close();
			
			System.out.println("i=" + i);
		}finally{
			JdbcUtils.free(rs, ps, conn);
		}
		
	}
}