计算机基础：SSM、Redis、MySQL等在Spring Boot中的应用与负载均衡详解

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本篇文章主要探讨了计算机工作的基本原理，涵盖了广泛的技术栈，包括SSM（Spring框架、Shiro Security、MyBatis）用于企业级应用开发，Redis作为内存数据库提供高效数据存储，MySQL作为关系型数据库管理数据，Spring Boot简化了应用程序的初始设置和部署，而Motan和Zookeeper则涉及到服务发现与负载均衡技术。在"搭建环境"部分，作者首先强调了理解计算机工作原理的重要性，然后介绍了如何将这些技术有效地集成到一个系统中。SSM架构是现代Java应用开发的基础，Spring Boot通过其轻量级特性减少了配置复杂性，使得快速开发成为可能。Redis的内存计算能力提高了数据读写速度，而MySQL则提供了稳定的数据持久化。此外，文章还涉及到了分布式系统中的组件如Motan，它是一个高性能、开源的服务调用框架，用于构建微服务架构。Zookeeper作为一个分布式协调服务，负责维护服务实例的状态和元数据，确保负载均衡的实现。通过Zookeeper，可以实现服务注册、发现以及集群管理，从而实现系统的高可用性和扩展性。逻辑运算单元（ALU）和算术逻辑单元（ALU）是处理器的核心组成部分，它们执行基本的逻辑操作，如NOT、AND、OR、XOR等，以及加法和比较。这些操作在处理指令时至关重要，比如在数据处理、决策制定和控制流程中。理解这些基本逻辑门的工作原理有助于开发者深入理解计算机底层机制。 "Doing Something Useful"部分强调了计算机是如何将这些底层原理结合到实际应用中，通过步骤详解展示了如何设计和实现一个能够执行有用功能的程序。从输入数据到处理、再到输出结果，每一个环节都依赖于计算机内部复杂的逻辑与协作。最后，文章还提到了控制流的概念，即程序如何根据条件决定执行路径，以及如何通过时钟周期管理整个计算机系统的同步。理解这些概念对于编写高效、可预测的代码至关重要。本文是一份实用的计算机工作基础指南，适合希望深入了解IT技术栈特别是软件开发过程的读者，无论是初学者还是经验丰富的开发者，都能从中获益匪浅。

be able to call it a bit. It could sit on a table with

either the “yes” or “no” showing. Then it would only

have two states.

You have probably heard of bits before in relation to

computers, and now you know what they are. In a

computer, the bits are not like the coin or the lock,

they are most like the light. That is, the bits in a

computer are places that either have electricity or they

do not. In a computer, the bits are very, very small and

there are a very large number of bits, but that’s all

that is in there.

Like the light in the living room, the bit is either on

or off. In the living room, there is electricity in the

wall coming into the switch. When you turn the switch

on, the electricity goes from the switch, through the

wires in the wall and ceiling, into the light socket and

then into the light bulb. So this bit in the living room

is several feet long, it includes the switch, the wires,

the socket and the light bulb. In a computer, bits are

mostly tiny, actually microscopic. Also, the computer

bit doesn’t have a mechanical switch at one end or a

light bulb at the other. If you removed the light bulb

from the socket in the living room, the switch would

still send electricity to the socket when it was on, and

it would still be a bit – you just wouldn’t be able to

see whether it was on or off by looking at a light bulb.

Your computer has something resembling switches, like

the keys on the keyboard, and something resembling light

bulbs, like the tiny dots on the screen, but most of the

bits are inside and unseen.

This is basically all there is in a computer – bits.

There are lots and lots of them, and they are arranged

and connected up in various ways, which we will examine

in detail as the book progresses, but this is what is

inside all computers – bits. A bit is always in one of

its two possible states, either off or on, and they

change between on and off when they are told to do so.

Computer bits aren’t like the coin that has to

physically flip over to change from one state to the

other. Bits don’t change shape or location, they don’t

look any different, they don’t move or rotate or get

bigger or smaller. A computer bit is just a place, if

there is no electricity in that place, then the bit is

off. When electricity is present, then the bit is on.

If you want to change a coin from showing heads to

showing tails, you have to physically move it to flip it

over, which takes some amount of time. Because the only

thing that has to move in a computer bit is the

electricity, changing it’s state from off to on, or on

to off can happen much more quickly than anything that

has to be moved physically.

As another example, remember the wild American west from

the movies? There were little towns separated by vast

distances. The bigger towns would have a telegraph

office. In this office was a guy wearing a funny hat who

had a spring-loaded switch called a key, and he would

send messages by pressing this key on and off in certain

patterns that represented the letters of the alphabet.

That key was connected to a battery (yes they had

batteries back then) and a wire that was strung along

poles until it got to another town. The key simply

connected the battery to the wire when it was pressed,

and disconnected the battery when the key was not

pressed. In the other town there was another telegraph

office, the wire came into that office, the end of it

was wrapped around an iron rod (which turns into a

magnet when there is electricity in the wire,) the

magnetized rod attracted a little bar of iron held

nearby with a spring, and made a clicking sound every

time the electricity came on. The guy in the office

listened to the pattern of the clicking and wrote down

the letters of the message. They might have used a light

bulb instead of the clicker, except that light bulbs had

not yet been invented.

The point of bringing up this subject, is that this

whole telegraph machine, from the key that gets pressed

in one town, through the long wire that travels to

another town many miles away, to the clicker, this whole

apparatus comprises just one single bit. It is a place

that can either have or not have electricity, and goes

on and off as it is told. And this method of

communication revolutionized the world in many ways. But

this very important invention of the 1840s consisted of

nothing more than one bit.

So I hope this begins to simplify the subject of

What the…?

Imagine it is a bright sunny day, and you walk into a

room with lots of open windows. You notice that the

ceiling light is on. You decide that this is a waste,

and you are going to turn the light off. You look at the

wall next to the door and see a switch plate with two

switches. So you assume that the one closer to the door

is for the ceiling light. But then you notice that the

switch is already off. And the other switch is off too.

So then you think “well, maybe someone installed the

switch upside down,” so you decide to flip the switch

anyway. You flip it on and off but nothing happens, the

ceiling light stays lit. So then you decide that it must

be the other switch, and you flip it on, off, on, off.

Again nothing happens, that ceiling light continues to

shine at you. You look around, there is no other door,

there are no other switches, no apparent way to turn off

this darned light. It just has to be one of these two

switches, who built this crazy house anyway? So you grab

one switch with each hand and start flipping them

wildly. Then suddenly you notice the ceiling light

flicker off briefly. So you slow down your switch

flipping and stop when the ceiling light is off. Both

switches say “on”, and the light is now off. You turn

one switch off, then on, and the light goes on, then

back off. This is backwards. One switch off equals light

on? So then you turn the other switch off, then on, the

same thing, the light goes on, then back off. What the

heck? Anyway, you finally figure out how it works. If

both switches are on, the light goes off. If one or the

other or both switches are off, then the ceiling light

is on. Kind of goofy, but you accomplish what you

intended, you turn both switches on, the light goes off,

and you get the heck out of this crazy room.

Now what is the purpose of this little story about the

odd light switches? The answer is, that in this chapter

we are going to present the most basic part that

computers are made of. This part works exactly like the

lighting system in that strange room.

This computer part is a simple device that has three

connections where there may or may not be some

electricity. Two of those connections are places where

electricity may be put into the device, and the third

connection is a place where electricity may come out of

the device.

Of the three connections, two of them are called

“inputs,” because electricity can be sent to them from

somewhere else. The third connection is called the

“output” because electricity can come out of it and then

be sent somewhere else.

This computer part is a device that does something with

bits. If you have two bits, and you connect those two

bits to the inputs, this device “looks” at those two

bits, and “decides” whether to turn the one output bit

on or off.

The way it “decides” is very simple, and is always the

same. If both inputs are on, the output will be off. If

one or both of the inputs are off, then the output will

be on. That’s just the way that the room with the odd

light switches worked.

Remember that there is nothing but bits inside the

computer. This simple device is where bits come from and

where they go to. The “decision” that this device makes

is how bits come to be turned on and off in a computer.

Two bits go into the device, and one bit comes out. Two

bits come from somewhere else, are examined by the

device, and a new third bit is generated so that it may

go somewhere else.

If you have been extra observant, you may have asked

yourself this question: “when both inputs are off, the

output is on, so…. how do you get electricity at the

output if both inputs are off?” Well, that is an

excellent question, and the excellent answer is that

every one of these devices is also connected to power.

Like every appliance or table lamp in your house, where

each has a plug with two pins, this device has a pair of

wires, one of which is connected to a place where the

electricity is always on, and the other is connected to

a place where the electricity is always off. This is

where the electricity for the output comes from. When

someone builds a computer, they have to make all of

those power connections to each one of those parts in

order to have it work, but when we are drawing diagrams

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