How to Build Dynamic React Apps with HarperDB Data

Connect Server URLs

Connect On-Prem (Server) URLs

As with standard OData feeds, if you wish to limit the fields returned, you can add a $select parameter to the query, along with other standard OData URL parameters, such as $filter, $orderby, $skip, and $top. See the help documentation for more information on supported OData queries.

Building a React Web Application

With Connect Server setup completed, you are ready to build the sample React app. The following steps walk through the source files for the React app contained in the .zip file, making note of any relevant sections of code.

index.html

This is the home page of the sample React web application. It fleshes out the HTML head and body and identifies the container and the script to display the web application.

main.js

This TypeScript file imports the necessary libraries, modules, and React class. The properties, or props, for the main React class are defined here as well.

package.json

This JSON file contains the properties, including dependencies, of the React app. This file is generated automatically.

webpack.config.js

This JavaScript file defines various configurations for the React app.

App.jsx

This JavaScript XML file contains the code needed to build the React app. The class App contains all of the functions needed to retrieve data from Connect Server and render the different parts of the React app. The methods are described below.

constructor

The constructor of the App class. In it, the state contains the dynamic data used to build the web app. You can also bind other methods on this so that you can modify the state within those methods.

  constructor(props) {
    super(props);

    this.state = {
      selectedTable: '',
      selectedColumns: [],
      tables: [],
      columns: [],
      tableData: [],
      auth: 'Basic ' + btoa(props.user + ':' + props.pass),
    };
    
    this.onTableChange = this.onTableChange.bind(this);
    this.onColumnChange = this.onColumnChange.bind(this);
    this.renderTableHeaders = this.renderTableHeaders.bind(this);
    this.renderTableBody = this.renderTableBody.bind(this);
    this.getColumnList = this.getColumnList.bind(this);
    this.getData = this.getData.bind(this);    
    
  }

componentDidMount

As per the React specification, the componentDidMount method is called before the render method and can be used to update the state variables of the app, after the constructor has run. In this method, you can send the HTTP request to Connect Server for the list of tables and set the tables and selectedTable state variables.

In the sample, a call to the getColumnList method retrieves the list of available columns for the first (and currently selected) table.

  componentDidMount() {
    Object.assign(axios.defaults, {headers: {"x-cdata-authtoken": this.state.auth}});
    axios.get(`${this.props.baseUrl}`)
      .then(res => {
        const tables = res.data.value;
        this.setState({ tables });
        this.setState({ selectedTable: tables[0].name});
      })
      .catch(function (error) {
        if (error.response) {
          alert('Code: ' 
            + error.response.data.error.code 
            + '\r\nMessage: ' 
            + error.response.data.error.message);
        } else {
          console.log('Error', error.message);
        }
      });
    this.getColumnList();
  }

getColumnList

This function retrieves the list of columns available for the selectedTable parameter (or the table currently selected in the UI if the parameter is undefined). It performs the HTTP request and parses the response, setting the columns and selectedColumns states.

  getColumnList(selectedTable) {
    if (!selectedTable) {
      selectedTable = this.state.selectedTable;
    }
    Object.assign(axios.defaults, {headers: {"x-cdata-authtoken": this.state.auth}});
    axios.get(`${this.props.baseUrl}/${selectedTable}/$metadata?@json`)
      .then(res => {
        let columns = res.data.items[0]["odata:cname"];
        this.setState({ 
          columns,
          selectedColumns: [], 
        });
      })
      .catch(error => {
        if (error.response) {
          alert('Code: '
            + error.response.data.error.code 
            + '\r\nMessage: ' 
            + error.response.data.error.message);
        } else {
          console.log('Error', error.message);
        }
      });
  }

renderTableList

This function uses the tables state variable to build out the options for the HTML drop-down select for selecting a table.

  renderTableList() {
    let tablesHTML = [];
    for (let i = 0; i < this.state.tables.length; i++) {
      let table = this.state.tables[i];
      tablesHTML.push({table.name});
    }
    return tablesHTML;
  }

renderColumnList

This function uses the columns state variable to build out the options for the HTML multi-select for selecting columns.

  
  renderColumnList() {
    let columnsHTML = [];
    for (let i = 0; i < this.state.columns.length; i++){
      let column = this.state.columns[i];
      columnsHTML.push({column});
    }
    return columnsHTML;
  }

renderTable

This function provides the basic framework for the HTML table based on the data retrieved from Connect Server. It uses two helper functions, renderTableHeaders() and renderTableBody(), to build the table headers and data rows.

  

  renderTable() {
    return (
      <table>
        <thead>
          { this.renderTableHeaders() }
        </thead>
        { this.renderTableBody() }
      </table>
    );
  }

renderTableHeaders

This function uses the selectedColumns state variable to build out the headers for the HTML table used to display the data from Connect Server.

  renderTableHeaders() {
    let headers = [];
    for (let i = 0; i < this.state.selectedColumns.length; i++) {
      let col = this.state.selectedColumns[i];
      headers.push(<th key={col}>{col}</th>)
    }
    return (<tr>{headers}</tr>);
  }

renderTableBody

This function uses the tableData and selectedColumns state variables to build out the data rows for the HTML table used to display the data from Connect Server.

  renderTableBody() {
    let rows = [];
    this.state.tableData.forEach(function(row) {
      rows.push(
        <tr key={btoa('row'+rows.length)}>
          {this.state.selectedColumns.map(col =>
            <td key={col}>{row[col]}</td>
          )}
        </tr>
      )
    }.bind(this));
    return (<tbody>{rows}</tbody>);
  }

getData

This function retrieves the data from Connect Server, building a list for the $select parameter based on the selectedColumns state variable and using the selectedTable state variable to determine which table to request data from. The data returned by Connect Server is stored in the tableData state variable.

  getData() {
    let columnList = '';
    columnList = this.state.selectedColumns.join(',');
    Object.assign(axios.defaults, {headers: {"x-cdata-authtoken": this.state.auth}});
    axios.get(`${this.props.baseUrl}/${this.state.selectedTable}/?$select=${columnList}`)
      .then(res => {
        const tableData = res.data.value;
        this.setState({ tableData });
      })
      .catch(error => {
        if (error.response) {
          alert('Code: ' 
            + error.response.data.error.code 
            + '\r\nMessage: ' 
            + error.response.data.error.message);
        } else {
          console.log('Error', error.message);
        }
      });
  }

onTableChange

This function handles the change event on the HTML drop-down select for choosing a table. In the function, the selectedTable state variable is set to the selected value and the tableData state variable is cleared of all values. Also, a call to the getColumnList function updates the HTML multi-select element for choosing columns.

  onTableChange(event) {
    const selectedTable = event.target.value;
    this.setState({
      selectedTable,
      tableData: [],
    });
    this.getColumnList(selectedTable);
  }

onColumnChange

This function handles the change event on the HTML multi-select for choosing columns to retrieve and display. After determining which columns are selected, the selectedColumns state variable is updated and the tableData state variable is cleared.

  onColumnChange(event) {
    let options = event.target.options;
    let selectedColumns = [];
    for (let i = 0; i < options.length; i++){
      if (options[i].selected){
        selectedColumns.push(options[i].value);
      }
    }
    this.setState({
      selectedColumns, 
      tableData: [],    
      });    
  }

render

This function is the function that controls the layout and display of the various HTML elements. It contains all of the static HTML features, as well as function calls to those functions that render the dynamic elements.

  
  render() {    
    return (
      <div>
        <h1>CData Connect Server React Demo</h1>
        <br/>
        <label>Select a Table</label>
        <br/>
        <select className='tableDropDown' onChange={this.onTableChange}>
          { this.renderTableList() }
        </select>
        <br/>
        <br/>
        <label>Select {this.state.selectedTable} Columns</label>
        <br/>
        <select className='columnMultiSelect' onChange={this.onColumnChange} multiple>
          { this.renderColumnList() }
        </select>
        <br/>
        <br/>
        { this.state.selectedColumns.length > 0 
          ? <button onClick={this.getData}>Get [{ this.state.selectedTable }] Data</button> 
          : null }
        <br/>
        <br/>
        { this.state.tableData.length > 0 
          ? this.renderTable() 
          : null }
      </div>
    );
  }

Configuring the React App

With the connection to data configured and the source files for the React app reviewed, you are now ready to run the React web application. You need to have node.js installed on your machine in order to run the React app. There are several modules that you also need to install before you can run the application.

Global Modules

In order to run the React App, install the babel and babel-cli modules globally from the command line:

• npm install -g babel
• npm install -g babel-cli

Setting Up the Project

In the next steps, you will set up your React project, creating and populating your package.json file.

1. In the command line, navigate to the directory with the source files:

   cd ./apiserver-react
   

2. Once in the directory, install the necessary modules using the preconfigured package.json file:

   npm install
   

Running the React App

Now that you have created your package.json file and installed the necessary modules, you are ready to run the React app. To do so, you can simply navigate to the directory for the React app in a command-line interface and execute the following command:

npm start

When the React app launches, the title and a drop-down menu to select a table are displayed. The list of tables is retrieved from the Connect Server and includes all of the tables you added as OData endpoints when configuring Connect Server.

When you select a table, the drop-down, multi-select menu for columns appears, and you can then select the columns you wish to see in your table. As you select columns, the table headers appear.

Once you select the table and columns, you can click the Get [Customers] Data button to retrieve data from your database via the API Server. The HTML table will be populated with data based on the table and columns you selected before clicking on the button.

Free Trial & More Information

Now that you have accomplished the steps needed to connect to your database data in dynamic webpages, sign up for a trial of Connect Server to start building dynamic webpages using live data from your cloud-based SaaS, Big Data, and NoSQL sources, including HarperDB! As always, our world-class support team is ready to answer any questions you may have.