JavaSelenium crawler basic installation tutorial to master automated testing from scratch

In modern software development, automated testing has become an important means to improve software quality and reduce manual intervention.

As a popular open source library, JavaSelenium provides powerful Web application testing capabilities.

This article will detail the basics of the JavaSelenium crawler, including installation steps, basic usage, and solutions to common problems.

Whether you are a beginner or an experienced developer, you can learn how to use Selenium for effective web crawling and data extraction through this article.

I. Environmental preparation.

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1. Install the Java development environment.

First, you need to make sure that the Java Development Environment (JDK) is installed on your computer.

You can download and install the latest version of JDK from Oracle's official website.

# 检查是否已安装Java
java -version

If not installed, please go to [Oracle official website] (https://www.oracle.com/java/technologies/javase-downloads.html) to download and install.

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2. Install Maven.

Maven is a project management tool that manages the construction, reporting and documentation of projects.

You can install Maven by using the following command:

# 下载Maven
wget https://archive.apache.org/dist/maven/maven-3/3.8.4/binaries/apache-maven-3.8.4-bin.tar.gz

# 解压Maven
tar -xvf apache-maven-3.8.4-bin.tar.gz

# 移动到/usr/local目录
sudo mv apache-maven-3.8.4 /usr/local/apache-maven

# 配置环境变量
echo "export M2_HOME=/usr/local/apache-maven" >> ~/.bashrc
echo "export PATH=$M2_HOME/bin:$PATH" >> ~/.bashrc
source ~/.bashrc

# 验证安装
mvn -version

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3. Create a Maven project.

Create a new project with Maven:

mvn archetype:generate -DgroupId=com.example -DartifactId=selenium-crawler -DarchetypeArtifactId=maven-archetype-quickstart -DinteractiveMode=false
cd selenium-crawler

II. Add Selenium dependencies.

In your pom.xmlAdd Selenium dependencies to the file:

    
        org.seleniumhq.selenium
        selenium-java
        4.0.0
    

After saving the file, run the following command to download the dependencies:

mvn clean install

III. Write the first Selenium script.

Insrc/main/java/com/exampleCreate a directory named SeleniumCrawler.javaFile, and add the following code:

package com.example;

import org.openqa.selenium.By;
import org.openqa.selenium.WebDriver;
import org.openqa.selenium.WebElement;
import org.openqa.selenium.chrome.ChromeDriver;
import java.util.List;

public class SeleniumCrawler {
    public static void main(String[] args) {
        // 设置ChromeDriver路径
        System.setProperty("webdriver.chrome.driver", "/path/to/chromedriver");

        // 初始化WebDriver
        WebDriver driver = new ChromeDriver();

        // 打开目标网页
        driver.get("https://www.example.com");

        // 查找页面元素并打印其文本内容
        List elements = driver.findElements(By.tagName("p"));
        for (WebElement element : elements) {
            System.out.println(element.getText());
        }

        // 关闭浏览器
        driver.quit();
    }
}

Make sure you have downloaded the corresponding version of ChromeDriver and replaced its path with /path/to/chromedriver。

You can download the driver suitable for your Chrome version at [ChromeDriver official website] (https://sites.google.com/a/chromium.org/chromedriver/downloads).

IV. Run the Selenium script.

Run the following commands in the terminal to execute your Selenium script:

mvn exec:java -Dexec.mainClass="com.example.SeleniumCrawler"

If everything works, you should see the console output all the

The text content of the label.

V. Frequently Asked Questions and Solutions.

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1. WebDriver cannot start.

If you encounter problems with WebDriver not starting, please check the following: - Make sure the version of ChromeDriver matches the version of the Chrome browser.

- Make sure ChromeDriver's path is correct and accessible.

-Make sure no other programs occupy the default port (usually 9515).

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2. Element not found.

If the script cannot find page elements, check the following: -Make sure the page is fully loaded.

Explicit waiting can be used to wait for specific elements to appear.

-Make sure the selector is correct.

For example, using By.id、By.name、By.classNameAnd other methods.

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3. Performance issues.

For large websites or websites that require frequent operation, the following optimization measures can be considered: -Use Headless Mode to reduce resource consumption.

-Minimize unnecessary page refreshes and redirects.

- Use a cache mechanism to store already crawled data.

VI. Summary.

Through the introduction of this article, you should have mastered the basic installation and usage of JavaSelenium crawler.

From environment preparation to writing simple Selenium scripts to solving common problems, each step provides you with detailed guidance.

Hope this content can help you make greater progress in automated testing and web crawling.

Continue to study Selenium in depth, and you will find more powerful functions and application scenarios.

I wish you a happy study!