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What is ASP.Net?

ASP.Net is a web development platform provided by Microsoft. It is used for creating web-based applications. chúng tôi was first released in the year 2002.

The first version of chúng tôi deployed was 1.0. The most recent version of chúng tôi is version 4.6. chúng tôi is designed to work with the HTTP protocol. This is the standard protocol used across all web applications.

ASP.Net applications can also be written in a variety of .Net languages. These include C#, chúng tôi and J#. In this chapter, you will see some basic fundamental of the .Net framework.

The full form of ASP is Active Server Pages, and .NET is Network Enabled Technologies.

ASP.NET Architecture and its Components

ASP.Net is a framework which is used to develop a Web-based application. The basic architecture of the chúng tôi framework is as shown below.

ASP.NET Architecture Diagram

The architecture of chúng tôi framework is based on the following key components

Language – A variety of languages exists for .net framework. They are chúng tôi and C#. These can be used to develop web applications.

Library – The .NET Framework includes a set of standard class libraries. The most common library used for web applications in .net is the Web library. The web library has all the necessary components used to chúng tôi web-based applications.

Common Language Runtime – The Common Language Infrastructure or CLI is a platform. .Net programs are executed on this platform. The CLR is used for performing key activities. Activities include Exception handling and Garbage collection.

Below are some of the key characteristics of the chúng tôi framework

Code Behind Mode – This is the concept of separation of design and code. By making this separation, it becomes easier to maintain the chúng tôi application. The general file type of an chúng tôi file is aspx. Assume we have a web page called MyPage.aspx. There will be another file called chúng tôi which would denote the code part of the page. So Visual Studio creates separate files for each web page, one for the design part and the other for the code.

State Management – chúng tôi has the facility to control state management. HTTP is known as a stateless protocol. Let’s take an example of a shopping cart application. Now, when a user decides what he wants to buy from the site, he will press the submit chúng tôi application needs to remember the items the user choose for the purchase. This is known as remembering the state of an application at a current point in time. HTTP is a stateless protocol. When the user goes to the purchase page, HTTP will not store the information on the cart items. Additional coding needs to be done to ensure that the cart items can be carried forward to the purchase page. Such an implementation can become complex at times. But chúng tôi can do state management on your behalf. So chúng tôi can remember the cart items and pass it over to the purchase page.

Caching – chúng tôi can implement the concept of Caching. This improve’s the performance of the application. By caching those pages which are often requested by the user can be stored in a temporary location. These pages can be retrieved faster and better responses can be sent to the user. So caching can significantly improve the performance of an application.

ASP.Net is a development language used for constructing web-based applications. chúng tôi is designed to work with the standard HTTP protocol.

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Aws Aurora: Architecture, Pricing, Mysql, And Postgresql Compatibility

Companies may manage their data effectively and enhance the client experience with the help of Amazon’s Web Services. Using the clustered volume technique, AWS Aurora controls the data in its database and designates it for crisis backup. Like Amazon Aurora, MySQL and PostgreSQL are open-source databases. Its features enhance critical areas, including durability, protection, mobility, cost, and so on. It is less maintenance-intensive and faster than MySQL and PostgreSQL.

What is AWS Aurora? AWS Aurora Architecture

The conventional DBMS serves as the foundation for Aurora Database. The majority of the standard DBMS’s parts, including the Query Execution Engine, Transaction Manager, and Recovery Manager, are reused. However, it adds several adjustments to the conventional DBMS to enhance its scalability, availability, and reliability.

Aurora started by storing the data remotely rather than on the local disk. Aurora Database enhances the Disk Manager to work with remote storage, as seen in the image below. Aurora Database repeats the data to increase dependability. The data is typically replicated six times across three different data centers. With these many replications, it is extremely unlikely that user data will be lost. Aurora Database manages one copy of the data using a single virtual server (Amazon EC2). The EC2 instance’s local disk is where the data is kept. Aurora Database manages the replicated data using 6 EC2s spread over 3 data centers in our instance.

Aurora Database goes one step further to improve the system’s efficiency. Only the changelog is saved to the remote storage. Aurora Database only stores the changelog to 6 EC2 instances in our write example. When an EC2 instance gets a request to persist a changelog, it first saves it to the changelog on disk, as illustrated in the picture below. The changelog is then applied to the pages. This can significantly reduce network bandwidth use.

AWS Aurora Pricing

Costing $0.12 every ACU-hour, Aurora ACUs are twice as expensive as provided Aurora ACUs. This implies −

4 ACUs are required for the minimal current running cost − $350 monthly or $0.48 per hour

Thus, the basic monthly price for Aurora Serverless V2 is $350. Every auto-scale event will be priced at least $0.0005. Although provisioned Aurora has the same capacity, it costs $175 per month without the flexible serverless auto-scaling.

AWS will probably gradually lower the minimum running cost, but because of the cold start issues with the process-based design, they are unable to eliminate it. Even with supplied mode’s minimal capacity of two ACUs, the monthly cost would be $175. Additionally, this price excludes a variety of items, such as bandwidth, read replica processes, multi-region replication, main and backup storage, and read replica operations.

Pricing for On-Demand Instances

The fact that the Aurora program just requires you to pay for the capacity that is being utilized and does not require you to hunt for long-term plans or yearly billing is arguably its strongest feature. This is incredibly helpful if you need Aurora for a quick project or test, so only pay for what you require. Pricing is based on the per DB instance hour utilized until the instance is terminated or stopped.

MySQL Compatibility

MySQL Versions are compatible with Amazon Aurora and guarantee first-rate services, including MySQL 5.6 and MySQL 5.7. MyISAM is incompatible with Aurora, which only supports the InnoDB storage engine. Therefore, you must move your data to InnoDB if it is currently stored in MyISAM. Scalability and High Performance, Higher than MySQL by up to 5 times, Backtrack (which makes data backup quick and easy), Storage Auto-Scaling, Managed, Monitoring, Automatic Software Update, Migration Support, and Cost-Effective (pay per use).

PostgreSQL Compatibility

Amazon Aurora PostgreSQL is compatible with versions 9.6 and 10 of PostgreSQL. Since it improves database performance effectiveness, fixing PostgreSQL with Aurora is extremely adaptive.

The Amazon Relational Database Service gateway was used to launch the Aurora system, which is PostgreSQL compatible. Amazon Aurora is the system, with PostgreSQL as the version. High performance and scalability, three times PostgreSQL’s performance, Backtrack (which speeds up data backup), storage auto-scaling, highly secure, managed, monitoring, automatic software update, automatic, automatic software, migration support, and cost-effectiveness (pay per use) are all features of this database (as your storage demands rise, Amazon Aurora automatically expands the size of your database volume).

Conclusion

What Is Vmware Workstation And Is It Free?

Our Review Pros Run multiple virtual machines on the same PC Drag and drop files between the host and guests Forever-free version available Cons The free version doesn’t let you run multiple VMs at once

There are a few solutions to deploy multiple operating systems on different platforms. Perhaps the most obvious one is to purchase multiple PCs and install different OSes. But it’s not suitable for small-sized companies or individual entrepreneurs since it’s quite expensive.

There’s also the possibility to prepare your computer for dual boot, but this scenario is limited. We think that a better solution is to use OS virtualization software and virtual machines. And one of the best virtual machine software tools for the job is VMware Workstation.

Check out the system requirements, installation procedure, editions and features, as well as how to use VMware Workstation before reading our review.

VMware Workstation system requirements

The OS virtualization tool has a large setup package. Therefore, before you download it, make sure that your Windows system has the following recommendations:

64-bit x86 Intel or AMD Processor from 2011 or later

1.3GHz or faster core speed

2Gb RAM minimum/4Gb RAM recommended

1.2Gb free disk space + more for each virtual machine

Windows 10, 8, 7, 2024, 2012, 2008 (64-bit only)

3D graphics hardware acceleration recommended with 3Gb RAM, NVIDIA GeForce 9900GT (or newer), or ATI Radeon HD 2600 (or newer)

Administrative rights

How to install VMware Workstation

In addition to modifying the default setup folder, you can include an enhanced keyboard driver in the installation to ensure better handling for international keyboards and the ones with extra keys. A system reboot is required to complete setup if you opt for the driver.

The rest of the installation is pretty straightforward and doesn’t take long to finish. However, you should know that VMware Workstation installs some virtual network drivers, which means that you will be temporarily offline. As such, you should suspend any Internet activities during its setup.

VMware Workstation free edition

On the bright side, you can fully test VMware Workstation Pro in a 30-days free trial. At the end of the trial period, you can either purchase the pro edition or go back to the free version. It’s a bit expensive, but there are always VMware deals around the corner.

How to use VMware Workstation

Before creating a new virtual machine, you need an operating system ready for virtualization, whether it’s on an installer disc or ISO image. For instance, if you want to virtualize Windows 10, you could create an ISO file from any Windows 10 build.

Once you have the ISO or installer disc at hand, here’s how you can create a VM:

Pick the Installer disc or Installer disc image file (ISO) and browse your PC for the guest OS

Specify the virtual machine name and location (can be later changed)

Set the maximum disk size and store the VM as a single file or split it into multiple parts (if unsure, leave the default selection)

Review settings and confirm the creation of your new virtual machine

These steps can be repeated for any new virtual machines you want to add. Once you have everything set up, you can launch the VMs as easy as starting an application. If you are using VMware Workstation, you will be able to keep multiple VMs opened at once and easily transfer files or copy content between them with drag-and-drop support. Plus, you can easily delete virtual machines or export VMs to OVF format.

What is VMware Workstation?

All aspects considered, VMware Workstation is an excellent OS virtualization tool that gives you the possibility to create and run virtual machines with various operating systems on the same computer.

It might be a bit challenging getting used to, but it does a great job at keeping its options neatly organized in the graphical interface. Make sure to couple it with a powerful antivirus solution for VMware to stay safe.

VMware Workstation FAQ

Is VMware Workstation free?

Yes, there’s a free version called VMware Workstation Player, which has no time limitations. But some of its features are unavailable and can only be accessed by upgrading to VMware Workstation Pro. Also, it can only be used for personal or educational purposes, unless you buy a commercial license for VMware Workstation Player.

Which is better, VMware or VirtualBox?

VirtualBox is free and open-source, so the true competition is between VirtualBox and VMware Workstation Player. It’s a bit more difficult to install macOS on VMware Workstation Player (although possible) than on VirtualBox. The superior VMware Workstation features are available in VMware Workstation Pro, which isn’t free to use. Therefore, we have to give credit to VirtualBox.

Which virtual machine is best?

VMware Workstation is at the top of our list when it comes to the best virtual machine software for Windows. However, if you want to try something else, we suggest VitualBox, Hyper-V, and Citrix Hypervisor.

What Is Firmware? Definition And Types

Better known as ‘software for hardware,’ Firmware is a program that comes embedded in a piece of hardware such as a keyboard, hard drive, BIOS, or a video card. It is designed to give permanent instructions to communicate with other devices in a system and perform functions like basic input/output tasks.

What is Firmware?

Firmware, like drivers, has the same function but differs in a way that it is stored on the hardware device itself while drivers are installed inside the operating system. Also, firmware can start on its own and do what it is programmed or designed to do while drivers must be run by the operating system.

Types of firmware BIOS

The first thing to come to life after the computer is powered on is BIOS. It can interact with the hardware and check for any unknown errors. It then signals another program called bootloader which does the job of waking up the operating system sleeping inside the hard drive and put it in the random access memory. So, BIOS is primarily responsible for handling your computer’s hardware components and ensure that they function properly. Although good, the low-level software has remained almost unchanged for the last two decades, and because of this, it is now becoming outdated and un-supportive of modern technologies. For instance, BIOS still uses 16-bit code while most laptops and PCs run 32 and 64-Bit code.

EFI

Knowing your computer’s BIOS version can help you find if you have the most up-to-date version of the firmware. On Windows computers, you can get the firmware version information using the Command Prompt. Alternatively, you can use an upgrade assistant for your device.

Read: Check if your PC uses BIOS or UEFI.

Updating Firmware

Firmware updates are available from the hardware manufacturers. For instance, a firmware update for a network router may be released to fix bugs, security holes or enhance its capabilities.

Some firmware updates are applied normally and just seem like a regular software update. However, others can be quite time-consuming as they might involve copying the firmware to a portable drive and then loading it onto the device manually. That said, some devices, feature a dedicated section in the administrative console that lets you apply a firmware update or a user manual for a complete reference.

Read: Fix Firmware update failed in Windows.

It’s extremely important to make sure the device that’s receiving the firmware update does not shut down while the update is being applied. A partial firmware update leaves the firmware corrupted, which can seriously damage how the device works. So, just make sure that once you start a firmware updater, you let the update finish.

Benefits and Importance of Firmware Update

Firmware update not only improves the functionality and features of your device but also fixes the performance issues. Moreover, the firmware update also helps a device remain competitive with the newer models in the market.

The firmware updates also contain the latest security patches. When you update your firmware, these latest security patches are automatically applied to your system. These security updates help protect your device from such types of attacks. Hence, a firmware update is important to tackle the increasing firmware attacks.

Read: How to update Router Firmware.

Firmware vs. Software difference

Often, the word Firmware and software are used interchangeably, i.e., single or a collection of computer programs assigned with some task to do on the machine. But in reality, it’s the work that defines the roots of these categories (firmware and software) in which we put them.

For example, the software is virtual so it can be Copied, Changed, and Destroyed. It is often stored in memory that is easily accessible and even replaceable by the user. But in the case of firmware, the memory that it stores is often embedded in the device itself and is not replaceable by the user. This is done deliberately to prevent any tampering or removing as it is critical for the device to run and can cause serious consequences if removed.

Read: What are Device Drivers?

Also, software is often upgraded, and so the information stored in it is often modified/altered with each execution of the application. In contrast, the firmware does not really change much unless you modify the settings very often. There is also very little or no requirement to change the firmware of a device.

Firmware vs Hardware difference

As explained earlier in this article, Firmware is a program or set of instructions fed into a hardware device. This set of instructions is necessary for the hardware device to function properly. On the other hand, hardware refers to the components of a computer and any other device. Processor, motherboard, RAM, hard disks, sound cards, Network Interface Card (NIC), etc., are some examples of hardware.

Is firmware a type of hardware?

Firmware is not a type of hardware. It is completely different from the hardware. Hardware refers to the components of a device, like Integrated Circuit (IC), CPU, GPU, RAM, etc. On the other hand, firmware is a program embedded into a piece of hardware. Firmware contains the set of instructions necessary for performing different tasks by the hardware.

What happens if I don’t update my firmware?

Hope this explains what firmware means.

Now read: How to update BIOS.

What Is Green Finance And What Are Its Benefits?

blog / Finance How Does Green Finance Benefit Organizations and the World

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Climate change has emerged as the defining political and economic problem of this century and it is likely to stay so for the foreseeable future. Governments, investors, businesses, and private individuals worldwide are beginning to take action in response to the climate issue, especially on decarbonization techniques. Moving to a low-carbon or green economy would need extraordinary levels of fresh capital investment, notably in the form of green financing, to support activities that cut GHG emissions and assist firms in adapting to the effects of climate change. That makes it important to understand what is green finance and how it matters.

What is Green Finance?

Simply put, green finance is a loan or investment that promotes environmentally-positive activities, such as the purchase of ecologically-friendly goods and services or the construction of green infrastructure. As the hazards connected to ecologically destructive products and services rise, green finance is becoming a mainstream phenomenon. 

ALSO READ: Why is Sustainability Important for Companies? Is it Really Helpful?

Why Green Financing? Types of Green Financing

Now that we have an understanding of what is green finance, let’s explore its different types:

Green Mortgages

They allow lenders to provide better terms to home purchasers of properties with a high environmental sustainability rating or if the buyer agrees to invest in enhancing the environmental performance of a property. 

Green Loans

These are loans used to support environmental initiatives such as household solar panels, electric automobiles, energy efficiency projects, and more. 

Green Credit Cards

Green credit cards such as Aspirations’ Zero card plant a tree every time a customer makes a purchase. They enable customers to direct their expenditure toward green finance in order to have a lasting impact on the environment.

Green Banks

Green banks operate similarly to traditional banks, but they employ public funds to spur private investment in renewable energy and other environmentally friendly initiatives. According to a 2023 research, the number of green banks in the US increased from one to 20 between 2011 and 2023, investing $7 billion in renewable energy.

Green Bonds

Green bonds account for the vast bulk of green funding. They include bond investments, the earnings from which are used to support a variety of green initiatives such as renewable energy, clean transportation, and conservation, among others. 

Benefits of Green Finance Encourages Spread of Technologies and Development of Environmentally Friendly Infrastructure

Governments of developing countries are constructing infrastructure that will improve long-term resource management, increase a country’s competitiveness and channel private sector money into local green markets.

Produces a Comparative Advantage Adds Business Value Enhances Economic Prospects

Governments that promote green financing assist in protecting their societies from scarcity of resources. They do this by building and encouraging local markets for renewable energy, as well as entering new markets with high employment potential. 

ALSO READ: With No ‘Planet B’, Here’s Why Sustainability in Business is Important

Green Finance: Risk and Opportunity

The shift to a low-carbon economy necessitates significant investments, which can only be funded through profound private-sector engagement. The incorporation of Environmental, Social and Governance (ESG) factors into private investments transforms a risk management strategy into a driver of innovation and new possibilities that provides long-term value for the company and society. However, capital mobilization for green investments has been constrained due to a number of microeconomic obstacles. These include maturity mismatches between long-term green investments. Additionally, the typically short-term time horizons of investors also impacts capital mobilization. Further, financial and environmental policy approaches are not always integrated.

Most significantly, a standardized definition of ‘green’ and a taxonomy of green activities are required to assist investors and financial institutions in allocating money effectively and making educated judgments. To avoid ‘greenwashing’, the notion of green financing should be more explicit. 

A uniform set of basic green finance criteria is also required to shift capital flows toward green and sustainable initiatives, as well as for market and risk monitoring and benchmarking. Additionally, green finance assets might benefit from disclosure standards and norms. Voluntary green finance concepts and standards, supplemented by legislative incentives, must be applied and monitored across all asset classes.

Green Finance vs Sustainable Finance

While sustainable finance refers to financial tools that serve environmental and social goals, green finance is entirely concerned with environmental objectives. According to Bloomberg, sustainability and green financing accounted for one-third of all money movements in tracked assets under management in 2023, totaling $30.7 trillion.

The great majority of emissions emitted by investors are funded or from loans, investments, and other financial activities. Funded emissions contribute 700x more to the carbon footprint of financial organizations than operational emissions do. Green financing for investments, loans, and credit cards can help cut emissions.

Green Finance in Banking Sector

Awareness of what is green finance has helped grow its relevance in the banking sector. Both commercial and investment banks are starting to take action in this regard. The actions include mainstreaming environmental factors into bank strategy and governance. It also includes mobilizing capital for specific green assets through loan origination, credit and savings product provision, and capital markets activities such as green bonds. This development is being driven by a variety of worldwide efforts, including the Principles for Responsible Banking and the Sustainable Banking Network.

Multilateral Development Banks (MDBs) also play an important role in mobilizing international climate funding and increasing financial leverage for low-carbon and climate-resilient projects. They do this through strengthening public and private investment planning, preparation, structure, financing, and de-risking. Many have made bold pledges to guarantee that their loan portfolios support conservation efforts and that natural capital and social consequences are factored into their investment decision-making processes.

Products of Green Finance

Green car loans

Green mortgages

Green home equity loans

Green certificate of deposits

Green cards

Green Finance Examples Green Bonds

These are bonds issued by governments, companies, or organizations to fund environmentally-friendly projects such as renewable energy, energy efficiency, and sustainable land use. Investors receive a financial return while also supporting projects that have a positive environmental impact. 

Sustainable Investment Funds

These are mutual funds or exchange-traded funds that invest in companies or projects that have a positive environmental impact. By investing in sustainable investment funds, individuals or organizations can support environmentally-friendly initiatives while also potentially earning a financial return on their investment. 

To summarize what is green finance, it can be described as a way for businesses and customers to minimize their carbon impact without burning a hole in their pockets. There are several types of green finance accessible to asset owners and enterprises. To learn more about this subject, explore Emeritus’ online courses on finance. 

By Siddhesh Shinde

Write to us at [email protected]

Using Android Architecture Components: Lifecycles And Sqlite Made Easy

Code

dependencies { implementation "android.arch.lifecycle:runtime:1.0.3" annotationProcessor "android.arch.lifecycle:compiler:1.0.0"

If you want to use Java 8.0 with the Lifecycles library, then you’ll also need to add the following:

Code

implementation "android.arch.lifecycle:common-java8:1.0.0"

The Lifecycles library introduces the following components:

Lifecycle – An abstract class that has an Android Lifecycle attached to it. Objects can observe this state and act accordingly.

LifecycleOwner – An interface that’s implemented by objects with a Lifecycle. Fragments and Activities already implement the LifecycleOwner interface (in Support Library 26.1.0+), and are therefore LifecycleOwners by default. You can observe LifecycleOwners— and any class that extends a LifecycleOwner— using a LifecycleObsever.

LifecycleObserver – LifecycleObserver receives updates about LifecycleOwner events. Prior to the Lifecycles library, you could only react to methods that were triggered by lifecycle events, like onCreate and onDestroy, but now you can create methods that are triggered by changes in a LifecycleOwner’s state. You can make a method lifecycle-aware by adding the @OnLifecycleEvent annotation.

Observer – An Observer receives an update whenever their assigned LifecycleOwner enters a new lifecycle state. An Observer that’s assigned to an Activity will be notified when this Activity enters a paused state, and again when it enters a resumed state. You add an Observer to a lifecycle, using lifecycle.addObserver(this).

ON_CREATE.

ON_DESTROY.

ON_PAUSE.

ON_RESUME.

ON_START.

ON_STOP .

ON_ANY.

ON_ANY is triggered by any lifecycle event. If you use Lifecycle.Event.ON_ANY, then the method should expect a LifecycleOwner and Lifecycle.Event argument.

Let’s look at how you’d create a LifecycleObserver that responds to changes in an Activity’s state. In the following code, we’re printing a message to Android Studio’s Logcat whenever the associated LifecycleOwner (MainActivity) enters a started or stopped state:

Code

import android.support.v7.app.AppCompatActivity; import android.os.Bundle; import android.arch.lifecycle.Lifecycle; import android.arch.lifecycle.LifecycleObserver; import android.util.Log; import android.arch.lifecycle.OnLifecycleEvent; public class MainActivity extends AppCompatActivity { private static final String TAG = "MainActivity"; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); getLifecycle().addObserver(new Observer()); } public class Observer implements LifecycleObserver { @OnLifecycleEvent(Lifecycle.Event.ON_START) public void onStart() { Log.e(TAG, "ON_START"); } @OnLifecycleEvent(Lifecycle.Event.ON_STOP) public void onStop() { Log.e(TAG, "ON_STOP"); }   }

Code

@OnLifecycleEvent({ON_STOP, ON_START})

If your project already has methods that handle lifecycle events, you can add the @OnLifecycleEvent annotation to these existing methods, rather than re-writing your current implementation.

Performing operations based on the Lifecycle state

You’ll usually only want to perform an operation when a Lifecycle is in a certain state.

For example, if you attempt to perform a FragmentTransaction after an Activity state has been saved, then the FragmentManager is going to throw an exception. By using getState.isAtLeast, you can ensure this operation only happens when the Lifecycle is in a compatible state:

Code

public void startFragmentTransaction() { if (lifecycle.getState.isAtLeast(STARTED)) { } }

The isAtLeast method can check for the following Lifecycle states:

INITIALIZED.

CREATED.

STARTED.

RESUMED.

DESTROYED.

You can also retrieve the current lifecycle state by calling getCurrentState().

LiveData: Keep track of changing data

Code

implementation "android.arch.lifecycle:extensions:1.0.0" Easier data storage with Room

Code

compile "android.arch.persistence.room:runtime:1.0.0-alpha1" 1. Database

The @Database class provides the bridge between your application and SQLite.

Your @Database class must be an abstract class that extends RoomDatabase, which defines tables present in your database, provides Data Access Objects (DAO) classes, and includes a list of entities associated with the database.

Code

//List the entities contained in your database. Separate multiple entities with a comma// @Database(entities = {List.class}, version = 1) public abstract class MyDatabase extends RoomDatabase { public abstract ItemDao itemDao(); }

You can acquire an instance of Database by calling Room.databaseBuilder() or Room.inMemoryDatabaseBuilder().

2. Entity

Room creates a table for each class that you annotate with @Entity, where each field corresponds to a column in the table. Entity classes are usually small model classes that don’t contain any logic.

Room can only persist fields it has access to, so you either need to make a field public, or provide getter and setter methods. Each entity also needs to define at least one field as a primary key. Even if there’s only a single field, you’ll still need to annotate that field with @PrimaryKey.

Code

@Entity public class List { @PrimaryKey private int id; private String item; public String getItem() { return item; } public void setItem(String item) { chúng tôi = item; }

Room uses the class name as the database table name, unless you override it using the tableName property:

Code

@Entity(tableName = "list")

Room also derives the column name from the field name, unless you explicitly define the column name using the @ColumnInfo(name = “column_name”) annotation, for example:

Code

@ColumnInfo(name = "productName")

Room creates a column for each field that’s defined in the entity. If there’s a field you don’t want to persist, then you’ll need to annotate it with @Ignore.

Code

@Entity public class List { ... ... ... @Ignore Bitmap image; }

Even though most object-relational mapping libraries let you map relationships from a database to the respective object model, Room doesn’t allow object references. The reasoning behind this restriction is that this type of lazy loading typically occurs on Android’s main UI thread, which can result in unresponsive user interfaces and application crashes. Instead, you’ll need to explicitly request the data your app requires.

3. DAO

@Insert. When you annotate a DAO method with @Insert, Room generates an implementation inserting all entries into the database in a single transaction.

@Update. Modifies entities in the database.

@Delete. Removes entities from the database.

@Query. This is the main annotation you’ll use in your DAO classes and it’s how you’ll perform all your read/write operations.

The following DAO interface contains various operations that we can perform on our table:

Code

@Dao public interface ItemDao { @Query("SELECT * FROM List") @Update void update(List list); @Delete void delete(List list); }

Each @Query method is checked against the table schemas at compile time. If there’s a problem with a query, you’ll get a compilation error rather than a runtime failure.

When performing queries, you’ll often want your application to update automatically when the data changes. You can achieve this by using Room in combination with LiveData – specifically, by using a return value of type LiveData in your query method. Room will then generate all the code necessary to update the LiveData when the database is updated.

Code

@Query("SELECT * FROM List")

If you’re using the RxJava library in your project,  you can create Room queries that return a backpressure-aware Flowable. Flowable is a new addition to RxJava 2.0 that helps you avoid the issue of a source Observable emitting items too quickly for the downstream Observer to process. This can result in a backlog of unconsumed, memory-hogging items.

To use RxJava with Room, you’ll need to add the following dependency to your module-level build.gradle file:

Code

implementation "android.arch.persistence.room:rxjava2:1.0.0"

If you’re interested in learning more about using RxJava 2.0 in combination with the Room library, then Google has published a Room and RxJava Sample app.

Wrapping up

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