Question

我正在尝试使用Typescript ES6 Class模块实现oracle连接。

我安装了@ types / oracledb软件包以及oracledb软件包。使用Jasmin框架。

以下是我已实施的代码。

import * as oracledb from 'oracledb';

export class ConnectionDAO{
/**
 * Connection Variable Declaration
 */
conn;

/**
 * Result Variable Declaration
 */
result;

/**
 *
 * Creates an instance of CommercialDAO.
 * To Initiate Connection and Make the connection utilized by @memberof CommercialDAO
 * @memberof CommercialDAO
 */
constructor() {
   this.conn = oracledb.getConnection({
        user: "commercial",
        password: "oracle",
        connectString: "localhost/COMMERCIALDB"
      }); 
}

public getRwCnt() {
    return new Promise(async function(resolve, reject) {
        try {
            let result = this.conn.execute('SELECT TESTCASEID FROM EXECUTE_TESTCASE');
            resolve(this.result.rows.length);
        } catch (err) { // catches errors in getConnection and the query
          reject(err);
        } 
        this.conn.release();
      });
}
}

错误：

TypeError: this.conn.execute is not a function

但是这个代码连接本身没有存储在'this.conn'变量中。

无论如何都要避免承诺和异步功能？有没有其他解决方案来实现这一目标？请提供有价值的解决方案和建议。期待样本片段。

Answer 1

错误的实际原因

TypeError: this.conn.execute is not a function

是因为this.conn很可能未定义。像这样添加支票。

public getRwCnt() {
  if(this.conn === undefined){
    console.log("The connection is not ready yet.");
    return;
... // Rest of your function
}

但这只会突出显示您有问题，而不能告诉您原因。

原因是您的构造函数严格同步。考虑具有一个等待构造函数完成的函数。

这是一个有效的版本：

import * as OracleDB from 'oracledb';

export class ConnectionDAO {
  /**
   * Connection Variable Declaration
   */
  public conn: OracleDB.IConnection;
  public connProm: OracleDB.IPromise<void>;

  /**
   * Result Variable Declaration
   */
  result;

  /**
   *
   * Creates an instance of CommercialDAO.
   * To Initiate Connection and Make the connection utilized by @memberof CommercialDAO
   * @memberof CommercialDAO
   */
  constructor() {
    this.connProm = OracleDB.getConnection({
      user: "hr",
      password: "hr",
      connectString: "localhost/XEPDB1"
    }).then(async (connection: OracleDB.IConnection) => {
      console.log("Connection finally created in constructor")
      this.conn = connection;
    }).catch((err: any) => {
      console.error(err.message);
    });
    console.log(" - Dumping Connection state in the end of the constructor", {conn: this.conn} , {connProm: this.connProm} );
  }

  public getRwCnt() {
    let me = this;
    return new Promise(async function (resolve, reject) {
      try {
        console.log(" - Dumping Connection state BEFORE waiting",{conn: me.conn} , {connProm: me.connProm} );
        await me.connProm;
        console.log(" - Dumping Connection state AFTER waiting",{connServerVersion: me.conn.oracleServerVersion } , {connProm: me.connProm} );
        let result = await me.conn.execute('SELECT count(*) FROM employees');
        resolve(result.rows);
      } catch (err) { // catches errors in getConnection and the query
        console.log("[Error] happened? - calling reject",err);
        reject(err);
      }
      if(me.conn) // Only release it it if it actually is set
        me.conn.release();
    });
  }
}

const d = new ConnectionDAO();

d.getRwCnt()
  .then((result)=>{console.log("RowCount",result)})
  .catch((err)=>{console.error("Promise rejected - ",err)})

console.log("Object constructor returned");

在ts-node上运行可以得到结果

 - Dumping Connection state in the end of the constructor { conn: undefined } { connProm: Promise { <pending> } }
 - Dumping Connection state BEFORE waiting { conn: undefined } { connProm: Promise { <pending> } }
Object constructor returned
Connection finally created in constructor
 - Dumping Connection state AFTER waiting { connServerVersion: 1804000000 } { connProm: Promise { undefined } }
RowCount [ [ 107 ] ]

Answer 2

似乎您在函数getRwCnt()中以错误的方式使用this。

请记住JavaScript中的每个函数都有自this。

选项1 将最高public getRwCnt() { let me = this; return new Promise(async function(resolve, reject) { try { let result = me.conn.execute('SELECT TESTCASEID FROM EXECUTE_TESTCASE'); resolve(this.result.rows.length); } catch (err) { // catches errors in getConnection and the query reject(err); } me.conn.release(); });分配给函数开头的另一个变量

public getRwCnt() {

        return new Promise(async (resolve, reject) => {
            try {
                let result = this.conn.execute('SELECT TESTCASEID FROM EXECUTE_TESTCASE');
                resolve(this.result.rows.length);
            } catch (err) { // catches errors in getConnection and the query
              reject(err);
            } 
            this.conn.release();
          });

选项2 使用ES6箭头功能

SELECT *
FROM tablename
WHERE count = (SELECT MAX(count) FROM tablename)

Answer 3

我尝试了您的解决方案，但看起来打字稿没有在等电话等待我.connectionPromise; 另外，不确定连接是否成功。我低于输出。

Inside constructor
get Connection executed....
 - Dumping Connection state in the end of the constructor { conn: undefined } { connProm: Promise { <pending> } }
Inside getRowNumbers function call....
Connection state BEFORE waiting:  { conn: undefined } { connectionPromise: Promise { <pending> } }
Object constructor returned

Somehow below output lines in your code are missing for me.

Connection finally created in constructor
 - Dumping Connection state AFTER waiting { connServerVersion: 1804000000 } { connProm: Promise { undefined } }
RowCount [ [ 107 ] ]

有没有办法使用typescript ES6类和模块连接oracledb？

3 个答案: