135 lines
3.7 KiB
JavaScript
135 lines
3.7 KiB
JavaScript
/* Copyright (c) 2016, 2019, Oracle and/or its affiliates. All rights reserved. */
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/******************************************************************************
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*
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* You may not use the identified files except in compliance with the Apache
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* License, Version 2.0 (the "License.")
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*
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* You may obtain a copy of the License at
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* http://www.apache.org/licenses/LICENSE-2.0.
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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*
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*
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* NAME
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* lobstream2.js
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*
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* DESCRIPTION
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* SELECTs a CLOB, streams it using 'data' events, and then displays it to the screen
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*
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* Use demo.sql to create the required table or do:
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* DROP TABLE mylobs;
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* CREATE TABLE mylobs (id NUMBER, c CLOB, b BLOB);
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*
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* Run lobinsert1.js to load data before running this example.
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*
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* This example requires node-oracledb 1.12 or later.
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*
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*****************************************************************************/
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var async = require('async');
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var oracledb = require('oracledb');
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var dbConfig = require('./dbconfig.js');
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var doconnect = function(cb) {
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oracledb.getConnection(
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{
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user : dbConfig.user,
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password : dbConfig.password,
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connectString : dbConfig.connectString
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},
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function(err, conn) {
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if (err) {
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return cb(err);
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} else {
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return cb(null, conn);
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}
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});
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};
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var dorelease = function(conn) {
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conn.close(function (err) {
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if (err)
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console.error(err.message);
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});
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};
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var doquery = function(conn, cb) {
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conn.execute(
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"SELECT c FROM mylobs WHERE id = 1",
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function(err, result) {
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if (err) {
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return cb(err, conn);
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}
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if (result.rows.length === 0) {
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return cb(new Error("No results. Did you run lobinsert1.js?"), conn);
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}
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var lob = result.rows[0][0];
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if (lob === null) {
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return cb(new Error("LOB was NULL"), conn);
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}
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return cb(null, conn, lob);
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});
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};
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// Stream a CLOB and builds up a String piece-by-piece
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var dostream = function(conn, clob, cb) {
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var errorHandled = false;
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var myclob = ""; // or myblob = Buffer.alloc(0) for BLOBs
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// node-oracledb's lob.pieceSize is the number of bytes retrieved
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// for each readable 'data' event. The default is lob.chunkSize.
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// The recommendation is for it to be a multiple of chunkSize.
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// clob.pieceSize = 100; // fetch smaller chunks to demonstrate repeated 'data' events
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clob.setEncoding('utf8'); // set the encoding so we get a 'string' not a 'buffer'
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clob.on(
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'error',
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function(err) {
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console.log("clob.on 'error' event");
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if (!errorHandled) {
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errorHandled = true;
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clob.close(function() {
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return cb(err, conn);
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});
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}
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});
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clob.on(
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'data',
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function(chunk) {
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console.log("clob.on 'data' event. Got %d bytes of data", chunk.length);
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// Build up the string. For larger LOBs you might want to print or use each chunk separately
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myclob += chunk; // or use Buffer.concat() for BLOBS
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});
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clob.on(
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'end',
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function() {
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console.log("clob.on 'end' event");
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console.log(myclob);
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});
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clob.on(
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'close',
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function() {
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console.log("clob.on 'close' event");
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if (!errorHandled) {
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return cb(null, conn);
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}
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});
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};
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// Connect and call the CLOB example
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async.waterfall([
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doconnect,
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doquery,
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dostream
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],
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function (err, conn) {
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if (err) { console.error("In waterfall error cb: ==>", err, "<=="); }
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if (conn)
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dorelease(conn);
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});
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