Parsing Log Files

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From the course by Duke University

Java Programming: Arrays, Lists, and Structured Data

984 оценки

Duke University

Java Programming: Arrays, Lists, and Structured Data

984 оценки

Course 2 of 4 in the Specialization Object Oriented Programming in Java

Build on the software engineering skills you learned in “Java Programming: Solving Problems with Software” by learning new data structures. Use these data structures to build more complex programs that use Java’s object-oriented features. At the end of the course you will write an encryption program and a program to break your encryption algorithm. After completing this course, you will be able to: 1. Read and write data from/to files; 2. Solve problems involving data files; 3. Perform quantitative analyses of data (e.g., finding maximums, minimums, averages); 4. Store and manipulate data in an array or ArrayList; 5. Combine multiple classes to solve larger problems; 6. Use iterables and collections (including maps) in Java.

From the lesson

Web Server Logs: From Logs to Visits

In this module, you will learn about how web server logs store information about visitors to a website, and you will write programs to access information like user IP address, date and time of access, and more. Using Java programs you write in this module, you will be able (1) to read information from a web server log, (2) to count the number of unique visitors to your website, and (3) to count the number of times each visitor uses your website.

Introduction1:19

Understanding Log Files6:30

LogEntry Class with toString5:50

Parsing Log Files3:00

Meet the Instructors

Andrew D. Hilton
Assistant Professor of the Practice
Electrical and Computer Engineering
Robert Duvall
Lecturer
Computer Science
Owen Astrachan
Professor of the Practice
Computer Science
Susan H. Rodger
Professor of the Practice
Computer Science

Hi, now that you've made your LogEntry class, you need to parse the lines

of the web server log to be able to create instances of the LogEntry class.

You'll do this by splitting the string into the appropriate fields

to pass values to the constructor for the LogEntry class.

You could accomplish this task with many indexOf and substring calls.

Although this task is not algorithmically hard, the code for it is very cumbersome.

For example, for the time portion of this entry,

you would need to turn the string in to a Date object.

The built in Java class from the Java.util package which represents a date and time.

Even though both the date and time class, as well as methods which parse strings,

are part of Java, the interface to the Date class is complex, especially

since the date format in the server logs is not the default format in Java.

For these reasons, we've provided code for you which will take a string from the web

server logs, parse it into appropriate fields, and return a log entry record.

To use this call WebLogParser.parseEntry and pass the string you want to parse.

The method returns a LogEntry object.

With that in mind, its time for you to starting the write the LogAnalyzer class.

For right now, you're gonna write code in the constructor to initialize the object,

and then write the read file method.

In later lessons, you'll write additional methods

that will perform that actually analysis of the log file that you've read in.

The first thing you would do to fill in the code for the constructor.

The constructor should initialize that the record fields to an empty ArrayList.

You've created ArrayLists in the past so

what you need to accomplish this task should be familiar.

The second thing you should do is fill in code for the readFile method.

This method will determine the file name to read from and then add log

entries to the records field to reflect the information from the file you opened.

To accomplish this task, you will want to make a FileResource for

the requested file.

You will then want to iterate over the FileResource's lines.

And for each line, you will use the WebLogParser.parseEntry method

to convert the line of text into a LogEntry.

Then you'll add that LogEntry to the records field, which as you may recall,

is an ArrayList.

When you've written a constructor and the readFile method,

you'll want to test out your code.

We've provided a convenient method called printAll, which will print

all the log entries you've stored in the instance variable records.

Remember the .toString method that we taught about?

System.out.println will make use of that .toString method to

represent the log entry as a string.

Once all this works, it will be time to start analyzing the data you've read in.

Happy coding.

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