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admin2025/6/29 1:35:30【news】
简介深色系网站,百度竞价代运营外包,kali 搭建wordpress,做网站推广多少钱经过测试：JAVA存取PostgreSQL的bytea类型均存在内存的限制问题(存取的数据过大会出现out of memory内存溢出的问题)，在EnterpriseDB对此做了优化。取PostgreSQL中的bytea，并存储到硬盘上./*** author Liu Yuanyuan*/private void getBytea{Co…
经过测试：JAVA存取PostgreSQL的bytea类型均存在内存的限制问题(存取的数据过大会出现out of memory内存溢出的问题)，在EnterpriseDB对此做了优化。
取PostgreSQL中的bytea，并存储到硬盘上.
/**
* @author Liu Yuanyuan
*/
private void getBytea
{
Connection conn = null;
Statement stmt = null;
ResultSet rs = null;
try
{
String driver = "org.postgresql.Driver";
String url = "jdbc:postgresql://" + "127.0.0.1" + ":" + "5866" + "/" + "db1";
Class.forName(driver);
System.out.println("find class");
conn = DriverManager.getConnection(url, "lyy", "lyy");
System.out.println("connected");
stmt = conn.createStatement();
String sql = "select obj from lyy.rawtable2 where id = 1";
rs = stmt.executeQuery(sql);
System.out.println("sql=" + sql);
while (rs.next())
{
System.out.println(rs.getMetaData().getColumnTypeName(1));
OutputStream ops = null;
InputStream ips = null;
File file = new File("e:" + File.separator + “binary”);
try
{
ips = rs.getBinaryStream(1);
byte[] buffer = new byte[ips.available()];//or other value like 1024
ops = new FileOutputStream(file);
for (int i; (i = ips.read(buffer)) > 0;)
{
ops.write(buffer, 0, i);
ops.flush();
}
}
catch (Exception ex)
{
ex.printStackTrace(System.out);
}
finally
{
ips.close();
ops.close();
}
}
}
catch (Exception ex)
{
ex.printStackTrace(System.out);
}
finally
{
try
{
If(rs!=null)
rs.close();
if(stmt!=null)
stmt.close();
if(conn!=null)
conn.close();
}
catch (SQLException ex)
{
Logger.getLogger(GetBlob.class.getName()).log(Level.SEVERE, null, ex);
}
}
}
向bytea直接插入二进制文件
Private void insertByteaByBase64()
{
String driver = "org.postgresql.Driver";
String url = "jdbc:postgresql://" + "127.0.0.1" + ":" + "5432" + "/" + "postgres";
Connection conn = null;
PreparedStatement ps = null;
ResultSet st = null;
try
{
Class.forName(driver);
System.out.println("success find class");
conn = DriverManager.getConnection(url, "postgres", "pg");
System.out.println("success connect");
String sql = "insert into blobtable(id,obj) values(?,?)";
ps = conn.prepareStatement(sql);
String fpath = “d:”+File. Separator + “image.jpg”;
File file = new File(fpath);
InputStream ips = new FileInputStream(file);
ps.setInt(1, 400);
ps.setBinaryStream(2, ips, (int) file.length());
ps.executeUpdate();
System.out.println("insert");
}
catch (Exception ex)
{
ex.printStackTrace(System.out);
}
finally
{
try
{
if(ps!=null)
ps.close();
if(conn!= null)
conn.close();
}
catch (SQLException ex)
{
ex.printStackTrace(System.out);
}
}
}
通过base64向bytea插入二进制文件
Private void insertByteaByBase64()
{
String driver = "org.postgresql.Driver";
String url = "jdbc:postgresql://" + "127.0.0.1" + ":" + "5432" + "/" + "postgres";
Connection conn = null;
PreparedStatement ps = null;
ResultSet st = null;
try
{
Class.forName(driver);
System.out.println("success find class");
conn = DriverManager.getConnection(url, "postgres", "pg");
System.out.println("success connect");
byte[] b = ByteaClass.getBytes();//得到数组byte[]
System.out.println("Length = " + b.length);
String s = Base64.encodeBytes(b, 0, b.length);
System.out.println("s = " + s.length());
String sql = "insert into blobtable(id,obj) values(?,?)";
String c = "decode(\'" + s + "\',\'base64\')";
sql = sql.replace("?,?", "?," + c);
System.out.println("sql = " + sql);
ps = conn.prepareStatement(sql);
ps.setInt(1, 400);
ps.executeUpdate();
System.out.println("insert");
}
catch (Exception ex)
{
ex.printStackTrace(System.out);
}
finally
{
try
{
if(ps!=null)
ps.close();
if(conn!= null)
conn.close();
}
catch (SQLException ex)
{
ex.printStackTrace(System.out);
}
}
}
