java 操作clob

之前在学校的时候做的都是练习，小儿科，遇到的情况完全都在自己的设想范围内。最近老是遇到字段溢出的情况，但是varchar2好像最长也只有4000个字符。所以不得不另辟蹊径，就找上了clob字段。

package test;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.Writer;

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

import oracle.sql.CLOB;

public class ClobTest {
	 private static Connection conn;  

	    static {
	        try {
	            Class.forName("oracle.jdbc.driver.OracleDriver");
	            conn = DriverManager.getConnection(
	                    "jdbc:oracle:thin:@localhost:1521:orcl","wch","wch123");
	        } catch (ClassNotFoundException e) {
	            e.printStackTrace();
	        } catch (SQLException e) {
	            e.printStackTrace();
	        }
	    }  

	    public static void main(String[] args) throws SQLException, IOException {
	      //  testInsert();
	       // testUpdate();
	        testRead();
	    }  

	    private static void testInsert() throws SQLException {
	        String sql = "insert into CLOBTEST values(1, empty_clob(),empty_clob())";
	        Statement stm = conn.createStatement();
	        stm.execute(sql);
	    }  

	    private static void testUpdate() throws SQLException, IOException {
	        String sql = "select context,c2 from CLOBTEST where id = 1 for update";
	        Statement stm = conn.createStatement();
	        ResultSet rs = stm.executeQuery(sql);
	        while (rs.next()) {
	            oracle.sql.CLOB c = (CLOB) rs.getClob(1);
	            Writer w = c.setCharacterStream(1);
	            w.write("wchwchwch\r\n");
	            w.write("哈哈哈\r\n哈哈哈ds", 2, 5);
	            w.flush();
	            w.close();
	            c = (CLOB) rs.getClob(2);
	            w = c.setCharacterStream(1);
	            w.write("dingsen");
	            w.flush();
	            w.close();
	        }
	        conn.commit();
	    }  

	    private static void testRead() throws SQLException, IOException {
	        String sql = "select context,c2 from CLOBTEST where id = 1";
	        PreparedStatement pstm = conn.prepareStatement(sql);
	        ResultSet rs = pstm.executeQuery();
	        System.out.println("-----------------------------------");
	        while (rs.next()) {
	            Clob clob = rs.getClob(1);
	            BufferedReader r = new BufferedReader(clob.getCharacterStream());
	            char[] cs = new char[10];
	            int total = 0;
	            StringBuilder sb = new StringBuilder();
	            while ((total = r.read(cs)) != -1) {
	                sb.append(cs,0,total);
	            }
	            System.out.println(sb.toString());
	        }
	    }
}