前言

在报表数据处理中，Excel公式拥有强大而多样的功能，广泛应用于各个业务领域。无论是投资收益计算、财务报表编制还是保险收益估算，Excel公式都扮演着不可或缺的角色。传统的做法是直接依赖Excel来实现复杂的业务逻辑，并生成相应的Excel文件。因此只需在预设位置输入相应参数，Excel公式即可被激活，迅速计算并呈现结果。正因如此，在这类场景中，企业积累了大量用于计算的Excel文件，它们已经成为了无价的财富。

然而，传统的Excel文件方式存在难以管理和数据不安全的缺点。为了解决这些问题，可以采用B/S架构+Excel组件库的方式。

本文将以个人所得税的计算为例，使用React+Spring Boot+GcExcel来实现。首先准备好Excel文件，按照国家税务总局提供的个税计算页面进行创建。

个人所得税的收入类型有8种：

• 工资薪金所得
• 年终奖所得
• 劳务报酬所得
• 个体工商户、生产经营所得
• 酬劳所得
• 偶然所得
• 利息、股息、红利所得
• 财产转让所得

其中，工资薪金所得最为复杂，包括社会保险和专项扣除。每种类型的计税方式都不同，为了便于理解，我们为每个类型创建了一个工作表进行计算。

以下是准备好的Excel文件，其中蓝色部分为需要输入参数的单元格，其他单元格将自动计算。

完成准备工作后，下面开始前后端工程的搭建。

实践

前端 React

创建React工程

新建一个文件夹，如TaxCalculator，进入文件夹，在资源管理器的地址栏里输入cmd，然后回车，打开命令行窗口。使用下面的代码创建名为client-app的react app。

npx create-react-app salary-client

进入刚创建的salary-client文件夹，使用IDE，比如VisualStudio Code打开文件夹。

界面部分

个人所得税涉及的收入类型一共有8种，其中（“酬劳所得”，“偶然所得”，“利息、股息、红利所得”，“财产转让所得”）四种的计算方式接近，UI布局相似，借助React的component特性，最终需要提供5种表单界面。

如下图所示：

为了让UI看起来更好看一些，可以先引入一个UI框架，这里我们使用了MUI。

npm install @mui/material @emotion/react @emotion/styled

首先，更新Src/App.js的代码，其中添加了DarkMode的Theme, 代码如下：

import './App.css';
import { ThemeProvider } from '@emotion/react';
import { createTheme } from '@mui/material';
import { FormContainer } from './Component/FormContainer';

const darkTheme = createTheme({
  palette: {
    mode: 'dark',
  },
});

function App() {
  return (
    <ThemeProvider theme={darkTheme}>
      <div className="App-header">
        <h2>个人所得税计算器</h2>
        <FormContainer></FormContainer>
      </div>
    </ThemeProvider>
  );
}

export default App;

可以看到，App.js中引用了FormContainer，下来添加 ./Component/FormContainer.js。

FormContainer主要是提供一个Selector，让用户选择收入类型，根据选择的类型渲染不同的组件。

import React, { useState } from 'react';
import { SalaryIncome } from "./SalaryIncome"
import { NativeSelect, FormControl } from '@mui/material';
import { BounsIncome } from './BounsIncome';
import { CommercialIncome } from './CommercialIncome';
import { LaborIncome } from './LaborIncome';
import { OtherIncome } from './OtherIncome';

export const FormContainer = () => {
    const [calcType, setCalcType] = useState("工资薪金所得");

    const GetIncomeControl = () => {
        switch (calcType) {
            case "工资薪金所得":
                return <SalaryIncome calcType={calcType}></SalaryIncome>;
            case "年终奖所得":
                return <BounsIncome calcType={calcType}></BounsIncome>;
            case "劳务报酬所得":
                return <LaborIncome calcType={calcType}></LaborIncome>;
            case "个体工商户、生产经营所得":
                return <CommercialIncome calcType={calcType}></CommercialIncome>;
            default:
                return <OtherIncome calcType={calcType}></OtherIncome>;
        }
    }

    return (
        <div style={{ width: "60vw", marginTop: "5vh" }}>
            <FormControl fullWidth sx={{ marginBottom: 2 }}>
                <NativeSelect labelId="demo-simple-select-label" id="demo-simple-select"
                    value={calcType} label="类型" onChange={e => setCalcType(e.target.value)}                    >
                    <option value="工资薪金所得">工资薪金所得</option>
                    <option value="年终奖所得">年终奖所得</option>
                    <option Item value="劳务报酬所得">劳务报酬所得</option>
                    <option value="个体工商户、生产经营所得">个体工商户、生产经营所得</option>
                    <option value="酬劳所得">酬劳所得</option>
                    <option value="偶然所得">偶然所得</option>
                    <option value="利息、股息、红利所得">利息、股息、红利所得</option>
                </NativeSelect>
            </FormControl>
            {GetIncomeControl()}
        </div>);
}

例如：; 同时会将calcType传递进去。

接下来，分别创建几个xxxIncome组件。

1.工资薪金所得 SalaryIncome.js

import React, { useState } from 'react';
import { TextField, Button, Stack } from '@mui/material';
import axios from 'axios';

export const SalaryIncome = (props) => {
    const [income, setIncome] = useState("");
    const [insurance, setInsurance] = useState("");
    const [childEdu, setChildEdu] = useState("");
    const [selfEdu, setSelfEdu] = useState("");
    const [treatment, setTreatment] = useState("");
    const [loans, setLoans] = useState("");
    const [rent, setRent] = useState("");
    const [elder, setElder] = useState("");

    const [taxableIncome, setTaxableIncome] = useState("");
    const [taxRate, setTaxRate] = useState("");
    const [deduction, setDeduction] = useState("");
    const [tax, setTax] = useState("");
    const [takeHomeSalary, setTakeHomeSalary] = useState("");

    async function calculateTax(event) {
        event.preventDefault();
        let res = await axios.post("api/calcPersonTax", {
            calcType: props.calcType,
            income: income,
            insurance: insurance,
            childEdu: childEdu,
            selfEdu: selfEdu,
            treatment: treatment,
            loans: loans,
            rent: rent,
            elder: elder,
        });
        if (res != null) {
            let data = res.data;
            setTaxableIncome(data.taxableIncome);
            setTaxRate(data.taxRate);
            setDeduction(data.deduction);
            setTax(data.tax);
            setTakeHomeSalary(data.takeHomeSalary);
        }
    }
    function reset(event) {
        event.preventDefault();
        setIncome("");
        setInsurance("");
        setChildEdu("");
        setSelfEdu("");
        setTreatment("");
        setLoans("");
        setRent("");
        setElder("");
        setTaxableIncome("");
        setTaxRate("");
        setDeduction("");
        setTax("");
        setTakeHomeSalary("");
    }

    return (
        <div>
            <Stack spacing={2} direction="row" sx={{ marginBottom: 2 }}>
                <TextField type="text" variant='outlined' color='primary'
                    label="税前工资" onChange={e => setIncome(e.target.value)}
                    value={income} fullWidth required size="small"/>
                <TextField type="text" variant='outlined' color='secondary'
                    label="社会保险/公积金" onChange={e => setInsurance(e.target.value)}
                    value={insurance} fullWidth size="small"/>
            </Stack>
            <Stack spacing={2} direction="row" sx={{ marginBottom: 2 }}>
                <TextField type="text" variant='outlined' color='secondary'
                    label="子女教育专项扣除" onChange={e => setChildEdu(e.target.value)}
                    value={childEdu} fullWidth size="small"/>
                <TextField type="text" variant='outlined' color='secondary'
                    label="继续教育专项扣除" onChange={e => setSelfEdu(e.target.value)}
                    value={selfEdu} fullWidth size="small"/>
            </Stack>
            <Stack spacing={2} direction="row" sx={{ marginBottom: 2 }}>
                <TextField type="text" variant='outlined' color='secondary'
                    label="大病医疗专项扣除" onChange={e => setTreatment(e.target.value)}
                    value={treatment} fullWidth size="small"/>
                <TextField type="text" variant='outlined' color='secondary'
                    label="住房贷款利息专项扣除" onChange={e => setLoans(e.target.value)}
                    value={loans} fullWidth size="small"/>
            </Stack>
            <Stack spacing={2} direction="row" sx={{ marginBottom: 2 }}>
                <TextField type="text" variant='outlined' color='secondary'
                    label="住房租金专项扣除" onChange={e => setRent(e.target.value)}
                    value={rent} fullWidth size="small"/>
                <TextField type="text" variant='outlined' color='secondary'
                    label="赡养老人专项扣除" onChange={e => setElder(e.target.value)}
                    value={elder} fullWidth size="small"/>
            </Stack>
            <Stack spacing={2} direction="row" sx={{ marginBottom: 2 }}>
                <TextField type="text" variant='outlined' color='secondary'
                    label="起征点" value="5000 元/月" fullWidth disabled size="small"/>
            </Stack>
            <hr></hr>
            <Stack spacing={2} direction="row" sx={{ marginBottom: 2 }}>
                <Button variant="outlined" color="primary" onClick={calculateTax} fullWidth size="large">计算</Button>
                <Button variant="outlined" color="secondary" onClick={reset} fullWidth size="large">重置</Button>
            </Stack>
            <hr></hr>
            <Stack spacing={2} direction="row" sx={{ marginBottom: 2 }}>
                <TextField type="text" variant='outlined' color='secondary'
                    label="应纳税所得额" value={taxableIncome} fullWidth disabled size="small"/>
                <TextField type="text" variant='outlined' color='secondary'
                    label="税率" value={taxRate} fullWidth disabled size="small"/>
            </Stack>
            <Stack spacing={2} direction="row" sx={{ marginBottom: 2 }}>
                <TextField type="text" variant='outlined' color='secondary'
                    label="速算扣除数" value={deduction} fullWidth disabled size="small"/>
                <TextField type="text" variant='outlined' color='secondary'
                    label="应纳税额" value={tax} fullWidth disabled size="small"/>
            </Stack>
            <Stack spacing={2} direction="row" sx={{ marginBottom: 2 }}>
                <TextField type="text" variant='outlined' color='secondary'
                    label="税后工资" value={takeHomeSalary} fullWidth disabled size="small"/>
            </Stack>

        </div>
    )
}

2.年终奖金所得 BounsIncome.js

import React, { useState } from 'react';
import { TextField, Button, Stack } from '@mui/material';
import axios from 'axios';

export const BounsIncome = (props) => {
    const [income, setIncome] = useState("");

    const [taxableIncome, setTaxableIncome] = useState("");
    const [taxRate, setTaxRate] = useState("");
    const [deduction, setDeduction] = useState("");
    const [monthlyWage, setMonthlyWage] = useState("");
    const [tax, setTax] = useState("");
    const [takeHomeSalary, setTakeHomeSalary] = useState("");

    async function calculateTax(event) {
        event.preventDefault();
        let res = await axios.post("api/calcPersonTax", {
            calcType: props.calcType,
            income: income,
        });
        if (res != null) {
            let data = res.data;
            setTaxableIncome(data.taxableIncome);
            setTaxRate(data.taxRate);
            setDeduction(data.deduction);
            setMonthlyWage(data.monthlyWage);
            setTax(data.tax);
            setTakeHomeSalary(data.takeHomeSalary);
        }
    }
    function reset(event) {
        event.preventDefault();
        setIncome("");
        setTaxableIncome("");
        setTaxRate("");
        setDeduction("");
        setMonthlyWage("");
        setTax("");
        setTakeHomeSalary("");
    }

    return (
        <div>
            <Stack spacing={2} direction="row" sx={{ marginBottom: 2 }}>
                <TextField type="text" variant='outlined' color='primary' size="small"
                    label="税前工资" onChange={e => setIncome(e.target.value)}
                    value={income} fullWidth required />
            </Stack>
            <hr></hr>
            <Stack spacing={2} direction="row" sx={{ marginBottom: 2 }}>
                <Button variant="outlined" color="primary" onClick={calculateTax} fullWidth size="large">计算</Button>
                <Button variant="outlined" color="secondary" onClick={reset} fullWidth size="large">重置</Button>
            </Stack>
            <hr></hr>
            <Stack spacing={2} direction="row" sx={{ marginBottom: 2 }}>
                <TextField type="text" variant='outlined' color='secondary' size="small"
                    label="应纳税所得额" value={taxableIncome} fullWidth disabled />
                <TextField type="text" variant='outlined' color='secondary' size="small"
                    label="税率" value={taxRate} fullWidth disabled />
            </Stack>
            <Stack spacing={2} direction="row" sx={{ marginBottom: 2 }}>
                <TextField type="text" variant='outlined' color='secondary' size="small"
                    label="速算扣除数" value={deduction} fullWidth disabled />
                <TextField type="text" variant='outlined' color='secondary' size="small"
                    label="平均每月工资" value={monthlyWage} fullWidth disabled />
            </Stack>
            <Stack spacing={2} direction="row" sx={{ marginBottom: 2 }}>
                <TextField type="text" variant='outlined' color='secondary' size="small"
                    label="应纳税额" value={tax} fullWidth disabled />
                <TextField type="text" variant='outlined' color='secondary' size="small"
                    label="税后工资" value={takeHomeSalary} fullWidth disabled />
            </Stack>

        </div>
    )
}

3.劳务报酬所得 LaborIncome.js

import React, { useState } from 'react';
import { TextField, Button, Stack } from '@mui/material';
import axios from 'axios';

export const LaborIncome = (props) => {
    const [income, setIncome] = useState("");

    const [taxableIncome, setTaxableIncome] = useState("");
    const [taxRate, setTaxRate] = useState("");
    const [deduction, setDeduction] = useState("");
    const [nonTaxablePart, setNonTaxablePart] = useState("");
    const [tax, setTax] = useState("");
    const [takeHomeSalary, setTakeHomeSalary] = useState("");

    async function calculateTax(event) {
        event.preventDefault();
        let res = await axios.post("api/calcPersonTax", {
            calcType: props.calcType,
            income: income,
        });
        if (res != null) {
            let data = res.data;
            setTaxableIncome(data.taxableIncome);
            setTaxRate(data.taxRate);
            setDeduction(data.deduction);
            setNonTaxablePart(data.nonTaxablePart);
            setTax(data.tax);
            setTakeHomeSalary(data.takeHomeSalary);
        }
    }
    function reset(event) {
        event.preventDefault();
        setIncome("");
        setTaxableIncome("");
        setTaxRate("");
        setDeduction("");
        setNonTaxablePart("");
        setTax("");
        setTakeHomeSalary("");
    }

    return (
        <div>
            <Stack spacing={2} direction="row" sx={{ marginBottom: 2 }}>
                <TextField type="text" variant='outlined' color='primary' size="small"
                    label="税前工资" onChange={e => setIncome(e.target.value)}
                    value={income} fullWidth required />
            </Stack>
            <hr></hr>
            <Stack spacing={2} direction="row" sx={{ marginBottom: 2 }}>
                <Button variant="outlined" color="primary" onClick={calculateTax} fullWidth size="large">计算</Button>
                <Button variant="outlined" color="secondary" onClick={reset} fullWidth size="large">重置</Button>
            </Stack>
            <hr></hr>
            <Stack spacing={2} direction="row" sx={{ marginBottom: 2 }}>
                <TextField type="text" variant='outlined' color='secondary' size="small"
                    label="应纳税所得额" value={taxableIncome} fullWidth disabled />
                <TextField type="text" variant='outlined' color='secondary' size="small"
                    label="税率" value={taxRate} fullWidth disabled />
            </Stack>
            <Stack spacing={2} direction="row" sx={{ marginBottom: 2 }}>
                <TextField type="text" variant='outlined' color='secondary' size="small"
                    label="速算扣除数" value={deduction} fullWidth disabled />
                <TextField type="text" variant='outlined' color='secondary' size="small"
                    label="减除费用" value={nonTaxablePart} fullWidth disabled />
            </Stack>
            <Stack spacing={2} direction="row" sx={{ marginBottom: 2 }}>
                <TextField type="text" variant='outlined' color='secondary' size="small"
                    label="应纳税额" value={tax} fullWidth disabled />
                <TextField type="text" variant='outlined' color='secondary' size="small"
                    label="税后工资" value={takeHomeSalary} fullWidth disabled />
            </Stack>

        </div>
    )
}

4.个体工商户、生产经营所得 CommercialIncome.js

import React, { useState } from 'react';
import { TextField, Button, Stack } from '@mui/material';
import axios from 'axios';

export const CommercialIncome = (props) => {
    const [income, setIncome] = useState("");

    const [taxableIncome, setTaxableIncome] = useState("");
    const [taxRate, setTaxRate] = useState("");
    const [deduction, setDeduction] = useState("");
    const [tax, setTax] = useState("");
    const [takeHomeSalary, setTakeHomeSalary] = useState("");

    async function calculateTax(event) {
        event.preventDefault();
        let res = await axios.post("api/calcPersonTax", {
            calcType: props.calcType,
            income: income,
        });
        if (res != null) {
            let data = res.data;
            setTaxableIncome(data.taxableIncome);
            setTaxRate(data.taxRate);
            setDeduction(data.deduction);
            setTax(data.tax);
            setTakeHomeSalary(data.takeHomeSalary);
        }
    }
    function reset(event) {
        event.preventDefault();
        setIncome("");
        setTaxableIncome("");
        setTaxRate("");
        setDeduction("");
        setTax("");
        setTakeHomeSalary("");
    }

    return (
        <div>
            <Stack spacing={2} direction="row" sx={{ marginBottom: 2 }}>
                <TextField type="text" variant='outlined' color='primary' size="small"
                    label="税前工资" onChange={e => setIncome(e.target.value)}
                    value={income} fullWidth required />
            </Stack>
            <hr></hr>
            <Stack spacing={2} direction="row" sx={{ marginBottom: 2 }}>
                <Button variant="outlined" color="primary" onClick={calculateTax} fullWidth size="large">计算</Button>
                <Button variant="outlined" color="secondary" onClick={reset} fullWidth size="large">重置</Button>
            </Stack>
            <hr></hr>
            <Stack spacing={2} direction="row" sx={{ marginBottom: 2 }}>
                <TextField type="text" variant='outlined' color='secondary' size="small"
                    label="应纳税所得额" value={taxableIncome} fullWidth disabled />
                <TextField type="text" variant='outlined' color='secondary' size="small"
                    label="税率" value={taxRate} fullWidth disabled />
            </Stack>
            <Stack spacing={2} direction="row" sx={{ marginBottom: 2 }}>
                <TextField type="text" variant='outlined' color='secondary' size="small"
                    label="速算扣除数" value={deduction} fullWidth disabled />
                <TextField type="text" variant='outlined' color='secondary' size="small"
                    label="应纳税额" value={tax} fullWidth disabled />
            </Stack>
            <Stack spacing={2} direction="row" sx={{ marginBottom: 2 }}>
                <TextField type="text" variant='outlined' color='secondary' size="small"
                    label="税后工资" value={takeHomeSalary} fullWidth disabled />
            </Stack>

        </div>
    )
}

5.余下四种类型 OtherIncome.js

import React, { useState } from 'react';
import { TextField, Button, Stack } from '@mui/material';
import axios from 'axios';

export const OtherIncome = (props) => {
    const [income, setIncome] = useState("");

    const [taxableIncome, setTaxableIncome] = useState("");
    const [taxRate, setTaxRate] = useState("");
    const [tax, setTax] = useState("");
    const [takeHomeSalary, setTakeHomeSalary] = useState("");

    async function calculateTax(event) {
        event.preventDefault();
        let res = await axios.post("api/calcPersonTax", {
            calcType: props.calcType,
            income: income,
        });
        if (res != null) {
            let data = res.data;
            setTaxableIncome(data.taxableIncome);
            setTaxRate(data.taxRate);
            setTax(data.tax);
            setTakeHomeSalary(data.takeHomeSalary);
        }
    }
    function reset(event) {
        event.preventDefault();
        setIncome("");
        setTaxableIncome("");
        setTaxRate("");
        setTax("");
        setTakeHomeSalary("");
    }

    return (
        <div>
            <Stack spacing={2} direction="row" sx={{ marginBottom: 2 }}>
                <TextField type="text" variant='outlined' color='primary' size="small"
                    label={props.calcType} onChange={e => setIncome(e.target.value)}
                    value={income} fullWidth required />
            </Stack>
            <hr></hr>
            <Stack spacing={2} direction="row" sx={{ marginBottom: 2 }}>
                <Button variant="outlined" color="primary" onClick={calculateTax} fullWidth size="large">计算</Button>
                <Button variant="outlined" color="secondary" onClick={reset} fullWidth size="large">重置</Button>
            </Stack>
            <hr></hr>
            <Stack spacing={2} direction="row" sx={{ marginBottom: 2 }}>
                <TextField type="text" variant='outlined' color='secondary' size="small"
                    label="应纳税所得额" value={taxableIncome} fullWidth disabled />
                <TextField type="text" variant='outlined' color='secondary' size="small"
                    label="税率" value={taxRate} fullWidth disabled />
            </Stack>
            <Stack spacing={2} direction="row" sx={{ marginBottom: 2 }}>
                <TextField type="text" variant='outlined' color='secondary' size="small"
                    label="应纳税额" value={tax} fullWidth disabled />
                <TextField type="text" variant='outlined' color='secondary' size="small"
                    label="税后工资" value={takeHomeSalary} fullWidth disabled />
            </Stack>
        </div>
    )
}

此时，完成UI部分后，可以尝试运行起来，效果如下：

//通过代码运行React app
npm start

可以试着填一些数据，但是当我们点击计算时会报错，这是因为服务端还没有准备好。

前端请求部分

熟悉Axios的同学可以跳过这部分，前面的代码里，已经给出了Axois发送请求的代码。

可以看到无论是哪一种类型的组件，请求都发送到了相同的url（"api/calcPersonTax"），以SalaryIncome为例，代码如下：

async function calculateTax(event) {
        event.preventDefault();
        let res = await axios.post("api/calcPersonTax", {
            calcType: props.calcType,
            income: income,
            insurance: insurance,
            childEdu: childEdu,
            selfEdu: selfEdu,
            treatment: treatment,
            loans: loans,
            rent: rent,
            elder: elder,
        });
        if (res != null) {
            let data = res.data;
            setTaxableIncome(data.taxableIncome);
            setTaxRate(data.taxRate);
            setDeduction(data.deduction);
            setTax(data.tax);
            setTakeHomeSalary(data.takeHomeSalary);
        }
    }

可以看到，整个请求变得非常简单，主要是把state的值取出来，通过post请求发送到服务端，然后根据返回值，把数据重新设给state，这样就完成UI数据的更新了。

配置请求转发中间件

我们在请求时访问的是相对地址，React本身有一个nodeJS，默认的端口是3000，而Spring Boot的默认端口是8080。前端直接访问会有跨域的问题，因此我们要做一个代理的配置。

在src文件夹下面添加文件，名为setupProxy.js，代码如下：

const { createProxyMiddleware } = require('http-proxy-middleware');

module.exports = function(app) {
  app.use(
    '/api',
    createProxyMiddleware({
      target: 'http://localhost:8080',
      changeOrigin: true,
    })
  );
};

服务端 Spring Boot

创建工程及添加依赖

使用IDEA创建一个Spring Boot工程，如果使用的是社区（community）版本，不能直接创建Spring Boot项目，那可以先创建一个空项目，idea创建project的过程，就跳过了，这里我们以创建了一个gradle项目为例。

plugins {
    id 'org.springframework.boot' version '3.0.0'
    id 'io.spring.dependency-management' version '1.1.0'
    id 'java'
    id 'war'
}

group = 'org.example'
version = '1.0-SNAPSHOT'

repositories {
    mavenCentral()
}

dependencies {
    implementation 'org.springframework.boot:spring-boot-starter-web'
    implementation 'com.grapecity.documents:gcexcel:6.2.0'
    implementation 'javax.json:javax.json-api:1.1.4'
    providedRuntime 'org.springframework.boot:spring-boot-starter-tomcat'
    testImplementation('org.springframework.boot:spring-boot-starter-test')
}

test {
    useJUnitPlatform()
}

在dependencies 中，我们除了依赖Spring Boot之外，还添加了GcExcel的依赖，后面导出时会用到GcExcel，目前的版本是6.2.0。

添加API

在Application类上，添加属性 @RequestMapping("/api").，并添加 calcPersonTax API。

@Spring BootApplication
@RestController
@RequestMapping("/api")
public class SalaryTaxCalculator {
    public static void main(String[] args) {
        SpringApplication.run(SalaryTaxCalculator.class, args);
    }

    @PostMapping("/calcPersonTax")
    public CalcResult calcTax(@RequestBody CalcParameter par) {
        Workbook workbook = new Workbook();
        workbook.open(GetResourcePath());
        return CalcInternal(workbook, par);
    }

    private String GetResourcePath(){
        return Objects.requireNonNull(SalaryTaxCalculator.class.getClassLoader().getResource("PersonalTaxCalcEngine.xlsx")).getPath();
    }

    private CalcResult CalcInternal(Workbook workbook, CalcParameter par) {
        //todo
    }
}

可以看到在CalcInternal方法内，我们使用GcExcel，根据calcType来判断使用哪一个sheet来进行计算。对不同Sheet只需要通过GcExcel设值，并从特定的格子里取值即可。

同时，我们还需要创建两个类，CalcParameter和CalcResult。CalcParameter用于从request中把post的data解析出来，CalcResult用于在response中返回的数据。

CalcParameter:

public class CalcParameter {
    public String calcType;
    public double income;
    public double insurance;
    public double childEdu;
    public double selfEdu;
    public double treatment;
    public double loans;
    public double rent;
    public double elder;
}

CalcResult:

public class CalcResult {
    public double taxableIncome;
    public double taxRate;
    public double deduction;
    public double tax;
    public double takeHomeSalary;
    public double monthlyWage;
    public double nonTaxablePart;
}

使用GcExcel完成公式计算

前面我们定义了 CalcInternal，在 CalcInternal 中，我们需要使用GcExcel来完成公式计算。

GcExcel的公式计算是自动完成的，我们使用workbook打开Excel文件后，只需要set相关的value。之后在取值时，GcExcel会自动计算响应公式的值。

private CalcResult CalcInternal(Workbook workbook, CalcParameter par) {
        var result = new CalcResult();
        var sheet = workbook.getWorksheets().get(par.calcType);
        switch (par.calcType) {
            case "工资薪金所得" -> {
                sheet.getRange("B1").setValue(par.income);
                sheet.getRange("D1").setValue(par.insurance);
                sheet.getRange("B2").setValue(par.childEdu);
                sheet.getRange("D2").setValue(par.selfEdu);
                sheet.getRange("B3").setValue(par.treatment);
                sheet.getRange("D3").setValue(par.loans);
                sheet.getRange("B4").setValue(par.rent);
                sheet.getRange("D4").setValue(par.elder);
                result.taxableIncome = (double) sheet.getRange("B9").getValue();
                result.taxRate = (double) sheet.getRange("D9").getValue();
                result.deduction = (double) sheet.getRange("B10").getValue();
                result.tax = (double) sheet.getRange("D10").getValue();
                result.takeHomeSalary = (double) sheet.getRange("B11").getValue();
            }
            case "年终奖所得" -> {
                sheet.getRange("B1").setValue(par.income);
                result.taxableIncome = (double) sheet.getRange("B3").getValue();
                result.taxRate = (double) sheet.getRange("D3").getValue();
                result.deduction = (double) sheet.getRange("B4").getValue();
                result.monthlyWage = (double) sheet.getRange("D4").getValue();
                result.tax = (double) sheet.getRange("B5").getValue();
                result.takeHomeSalary = (double) sheet.getRange("D5").getValue();
            }
            case "劳务报酬所得" -> {
                sheet.getRange("B1").setValue(par.income);
                result.taxableIncome = (double) sheet.getRange("B3").getValue();
                result.taxRate = (double) sheet.getRange("D3").getValue();
                result.deduction = (double) sheet.getRange("B4").getValue();
                result.nonTaxablePart = (double) sheet.getRange("D4").getValue();
                result.tax = (double) sheet.getRange("B5").getValue();
                result.takeHomeSalary = (double) sheet.getRange("D5").getValue();
            }
            case "个体工商户、生产经营所得" -> {
                sheet.getRange("B1").setValue(par.income);
                result.taxableIncome = (double) sheet.getRange("B3").getValue();
                result.taxRate = (double) sheet.getRange("D3").getValue();
                result.deduction = (double) sheet.getRange("B4").getValue();
                result.tax = (double) sheet.getRange("D4").getValue();
                result.takeHomeSalary = (double) sheet.getRange("B5").getValue();
            }
            default -> {
                sheet.getRange("B1").setValue(par.income);
                result.taxableIncome = (double) sheet.getRange("B3").getValue();
                result.taxRate = (double) sheet.getRange("D3").getValue();
                result.tax = (double) sheet.getRange("B4").getValue();
                result.takeHomeSalary = (double) sheet.getRange("D4").getValue();
            }
        }
        return result;
    }

这样就完成了服务端的代码。

最终效果

我们可以使用工资薪金所得试验一下，可以看到数据被计算出来了。因为目的是为了分享服务端公式计算的方案，所以计算的结果是否正确，就不做细致考虑。

总结

个税计算的场景并不复杂，主要是通过Excel完成公式计算即可，在服务端使用GcExcel可以大幅度降低前后端的开发难度，系统的搭建过程可以完全不需要考虑计算的逻辑。

在实际的公式计算场景中，可能往往会比个税计算的场景复杂，借助GcExcel这样Excel组件库，可以很容易的把已有的Excel文件迁移到线上，提高工作效率。

另外，本文中分享的代码并不是最符合实际工作中的要求，读者还可以从以下角度去优化自己的代码。

1. 收入类型可以抽成枚举，这样维护和使用起来更容易。
2. 目前每一个react组件里的冗余度还不低，还可以继续抽象组件，避免重复写代码。
3. 在服务端，因为公式计算的逻辑是不会变的，在实际场景中，也有可能同一时间要加载复数个Excel文件，可以考虑把workbook常驻内存，来提高性能。

扩展链接：

高级SQL分析函数-如何用窗口函数进行排名计算

3D模型+BI分析，打造全新的交互式3D可视化大屏开发方案

React + Springboot + Quartz，从0实现Excel报表自动化