数据库中使用Clob处理长文本

长文本（Clob）和二进制文件（Blob）的处理难点其实不再JDBC上，而是在输入输出上。

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;


//大字符串处理
public class ClobTest {

    public static void main(String[]args) throws SQLException, IOException{
// create();
        read();
    }

    static void create() throws SQLException, IOException {
        Connection conn = null;
        PreparedStatement ps = null;
        ResultSet rs = null;

        try {
            conn = JdbcUtils.getConnection();
            String sql = "insert into clob_test(big_text)values(?)";
            ps = conn.prepareStatement(sql);

            File file=new File("src/cn/itcast/jdbc/JdbcUtils.java");
            Reader reader=new BufferedReader(new FileReader(file));

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

            int i = ps.executeUpdate();

            reader.close();
            System.out.println("i=" + i);

        } finally {
            JdbcUtils.free(rs, ps, conn);
        }
    }

    static void read() throws SQLException, IOException {
        Connection conn = null;
        Statement st = null;
        ResultSet rs = null;

        try {
            conn = JdbcUtils.getConnection();

            st = conn.createStatement();

            rs = st.executeQuery("select big_text from clob_test");

            while (rs.next()) {
                //读取大文本，方式1
                Clob clob=rs.getClob("big_text");   
                Reader reader=clob.getCharacterStream();

                //读取大文本，方式2
                //Reader reader=rs.getCharacterStream(1); 

                //读取大文本，方式3
                //String s=rs.getString(1); 
                //System.out.println();
                File file=new File("JdbcUtils.java");
                Writer writer=new BufferedWriter(new FileWriter(file));
                char[]buff=new char[1024];  //缓冲区
                for(int i=0;(i=reader.read(buff))>0;)
                    writer.write(buff,0,i);

                writer.close();
                reader.close();
            }

        } finally {
            JdbcUtils.free(rs, st, conn);
        }
    }
}