Angular Access Control CanActivate Route Guard Example

In your Angular application you may need to control access to different parts of your app. To control that kind of authorization and authentication you can use route guards in Angular.

Using route guards, you can perform some action before navigating to another route and you can restrict access to routes based on the outcome of that action. In this post we’ll see example of using CanActivate route guard to restrict access to route based on whether user is authenticated or not.

Table of contents

1. Why route guards in Angular
2. Route guard interfaces in Angular
3. CanActivate interface in Angular
4. How to use CanActivate routeguard
5. Authentication using CanActivate routeguard Angular example
6. Using CanActivateFn in Angular

Why route guards in Angular

Use of route guards to control access in your Angular app may be considered for following scenarios-

• User is not authorized to navigate to the component rendered by the route user want to navigate to.
• User is not authenticated (not logged in).
• You need to fetch some data before you display the target component.
• You want to save pending changes before leaving a component.
• You want to ask the user if it's OK to discard pending changes rather than save them.

How to Read File From The Last Line in Java

There are applications where you have to read huge files line by line may be using some tool like Pentaho, Camel. Let's say these files are in the format header, records and footer and you need to check something in the footer (last line of the file) and if that condition is not met you need to reject the file. Now, reading line by line in such scenario, will be wasteful as you'll anyway reject the file in the end.

So for such scenarios it is better to read the last line (or may be last N lines) of the file, to have better throughput. In this post you will see how to read a file from the last line in Java.

Table of contents

1. Java program to read last line of the file using RandomAccessFile
2. Java program to read last n lines of the file
3. Read file from the last line using ReversedLinesFileReader

In Java reading file from the end can be done using RandomAccessFile which has a seek method to set the file-pointer offset, measured from the beginning of the file.

Apache Commons IO also has a ReversedLinesFileReader class which reads lines in a file reversely.

File used

Let's say you have a file aa.txt which has the following content-

This is the first line.
This is the second line.
This is the third line.
This is the fourth line.

And you want to read last line of this file using Java.