105 lines
3.1 KiB
JavaScript
105 lines
3.1 KiB
JavaScript
/* Copyright (c) 2016, 2020, 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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* This example requires node-oracledb 1.12 or later.
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*
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* This example uses Node 8's async/await syntax.
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*
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*****************************************************************************/
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const oracledb = require('oracledb');
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const dbConfig = require('./dbconfig.js');
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const demoSetup = require('./demosetup.js');
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async function run() {
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let connection;
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try {
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connection = await oracledb.getConnection(dbConfig);
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await demoSetup.setupLobs(connection, true); // create the demo table with data
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//
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// Fetch a CLOB and write to the console
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//
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let result = await connection.execute(`SELECT c FROM no_lobs WHERE id = 1`);
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if (result.rows.length === 0) {
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throw new Error("No row found");
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}
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const clob = result.rows[0][0];
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if (clob === null) {
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throw new Error("LOB was NULL");
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}
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// Stream a CLOB and builds up a String piece-by-piece
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const doStream = new Promise((resolve, reject) => {
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let 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('error', (err) => {
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// console.log("clob.on 'error' event");
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reject(err);
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});
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clob.on('data', (chunk) => {
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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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// console.log("clob.on 'data' event. Got %d bytes of data", chunk.length);
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myclob += chunk; // or use Buffer.concat() for BLOBS
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});
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clob.on('end', () => {
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// console.log("clob.on 'end' event");
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clob.destroy();
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console.log(myclob);
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});
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clob.on('close', () => {
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// console.log("clob.on 'close' event");
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resolve();
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});
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});
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await doStream;
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} catch (err) {
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console.error(err);
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} finally {
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if (connection) {
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try {
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await connection.close();
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} catch (err) {
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console.error(err);
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}
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}
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}
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}
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run();
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