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Java，SpringBoot，接收Get、Post及不同Content-Type，类型转换

xiyangw 2022-11-24 17:00 47 浏览 0 评论

HTTP Content-Type：

GET请求URL传递参数（Content-Type可能为空）：

功能描述：URL地址传递参数，通用：@RequestParam、@PathVariable和对象接收，局部类型转换（日期类型）。

package com.what21.demo.controller;

import com.alibaba.fastjson.JSON;
import com.what21.demo.controller.param.UrlEncodedTransfer;
import org.springframework.beans.propertyeditors.CustomDateEditor;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.WebDataBinder;
import org.springframework.web.bind.annotation.*;
import org.springframework.web.context.request.WebRequest;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Arrays;
import java.util.Date;
import java.util.Map;

@Controller("/urlParamTransfer")
@RequestMapping("/urlParamTransfer")
public class UrlParamTransferController {

    @RequestMapping(path = "/bean1")
    @ResponseBody
    public Object bean1(HttpServletRequest request, HttpServletResponse response) {
        Map<String, String[]> paramsMap = request.getParameterMap();
        if (paramsMap != null) {
            for (String key : paramsMap.keySet()) {
                System.out.println(key + "=" + Arrays.toString(paramsMap.get(key)));
            }
        }
        return JSON.toJSONString(paramsMap);
    }

    @RequestMapping(path = "/bean2")
    @ResponseBody
    public Object bean2(HttpServletRequest request, @RequestParam("id") Integer id, @RequestParam("name") String[] names,
                        @RequestParam("date") String dateStr) {
        UrlEncodedTransfer urlParamTransfer = new UrlEncodedTransfer();
        urlParamTransfer.setId(id);
        urlParamTransfer.setName(Arrays.toString(names));
        try {
            DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
            urlParamTransfer.setDate(dateFormat.parse(dateStr));
        } catch (Exception e) {
            e.printStackTrace();
        }
        return JSON.toJSONString(urlParamTransfer);
    }

    @RequestMapping(path = "/bean3/{id}/{name}/{date}")
    @ResponseBody
    public Object bean3(HttpServletRequest request, @PathVariable("id") Integer id, @PathVariable("name") String name,
                        @PathVariable("date") String dateStr) {
        UrlEncodedTransfer urlParamTransfer = new UrlEncodedTransfer();
        urlParamTransfer.setId(id);
        urlParamTransfer.setName(name);
        try {
            DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
            urlParamTransfer.setDate(dateFormat.parse(dateStr));
        } catch (Exception e) {
            e.printStackTrace();
        }
        return JSON.toJSONString(urlParamTransfer);
    }

    /**
     * 局部转换
     *
     * @param binder
     * @param request
     */
    @InitBinder
    public void initBinder(WebDataBinder binder, WebRequest request) {
        //转换日期
        DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        // CustomDateEditor为自定义日期编辑器
        binder.registerCustomEditor(Date.class, new CustomDateEditor(dateFormat, true));
    }

    @RequestMapping(path = "/bean4")
    @ResponseBody
    public Object bean4(HttpServletRequest request, @RequestParam("id") Integer id, @RequestParam("name") String[] names,
                        @RequestParam("date") Date date) {
        UrlEncodedTransfer urlParamTransfer = new UrlEncodedTransfer();
        urlParamTransfer.setId(id);
        urlParamTransfer.setName(Arrays.toString(names));
        urlParamTransfer.setDate(date);
        return JSON.toJSONString(urlParamTransfer);
    }

    @RequestMapping(path = "/bean5/{id}/{name}/{date}")
    @ResponseBody
    public Object bean5(HttpServletRequest request, @PathVariable("id") Integer id, @PathVariable("name") String name,
                        @PathVariable("date") Date date) {
        UrlEncodedTransfer urlParamTransfer = new UrlEncodedTransfer();
        urlParamTransfer.setId(id);
        urlParamTransfer.setName(name);
        urlParamTransfer.setDate(date);
        return JSON.toJSONString(urlParamTransfer);
    }

    @RequestMapping(path = "/bean6")
    @ResponseBody
    public Object bean6(HttpServletRequest request, UrlEncodedTransfer urlParamTransfer) {
        System.out.println(">>>>" + request.getHeader("Content-Type"));
        return JSON.toJSONString(urlParamTransfer);
    }

}

package com.what21.demo.controller.param;

import lombok.Data;

import java.util.Date;

@Data
public class UrlEncodedTransfer {

    private Integer id;

    private String name;

    private Date date;

}

功能测试：

#bean1
http://127.0.0.1:8080/urlParamTransfer/bean1?id=123&name=名称&name=名称2&date=1995-09-15 12:12:12
{"id":["123"],"name":["名称","名称2"],"date":["1995-09-15 12:12:12"]}

#bean2
http://127.0.0.1:8080/urlParamTransfer/bean2?id=123&name=名称&name=名称2&date=1995-09-15 12:12:12
{"date":811138332000,"id":123,"name":"[名称, 名称2]"}

#bean3
http://127.0.0.1:8080/urlParamTransfer/bean3/123/名称/1995-09-15 12:12:12
{"date":811138332000,"id":123,"name":"名称"}

#bean4
http://127.0.0.1:8080/urlParamTransfer/bean4?id=123&name=名称&name=名称2&date=1995-09-15 12:12:12
{"date":811138332000,"id":123,"name":"[名称, 名称2]"}

#bean5
http://127.0.0.1:8080/urlParamTransfer/bean5/123/名称/1995-09-15 12:12:12
{"date":811138332000,"id":123,"name":"名称"}

#bean6
http://127.0.0.1:8080/urlParamTransfer/bean6?id=123&name=名称&date=1995-09-15 12:12:12&name=名称2
{"date":811138332000,"id":123,"name":"名称,名称2"}

Header头传递参数

功能描述：HTTP协议头传递参数，使用@RequestHeader接收参数。

package com.what21.demo.controller;

import com.alibaba.fastjson.JSON;
import com.what21.demo.controller.param.HeaderTransfer;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestHeader;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Arrays;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.Map;

@Controller("/headerTransfer")
@RequestMapping("/headerTransfer")
public class HeaderTransferController {

    @RequestMapping(path = "/bean1")
    @ResponseBody
    public Object bean1(HttpServletRequest request, HttpServletResponse response) {
        Map<String, Object> headerMap = new HashMap<>();
        Enumeration<String> enumer = request.getHeaderNames();
        while (enumer.hasMoreElements()) {
            String headName = (String) enumer.nextElement();
            String headValue = request.getHeader(headName);
            headerMap.put(headName, headValue);
        }
        return JSON.toJSONString(headerMap);
    }

    @RequestMapping(path = "/bean2")
    @ResponseBody
    public Object bean2(HttpServletRequest request, @RequestHeader("id") Integer id, @RequestHeader("name") String[] names,
                        @RequestHeader("date") String dateStr) {
        HeaderTransfer headerTransfer = new HeaderTransfer();
        headerTransfer.setId(id);
        headerTransfer.setName(Arrays.toString(names));
        try {
            DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
            headerTransfer.setDate(dateFormat.parse(dateStr));
        } catch (Exception e) {
            e.printStackTrace();
        }
        return JSON.toJSONString(headerTransfer);
    }

}

package com.what21.demo.controller.param;

import lombok.Data;

import java.util.Date;

@Data
public class HeaderTransfer {

    private Integer id;

    private String name;

    private Date date;

}

功能测试：

#bean1
http://127.0.0.1:8080/headerTransfer/bean1
{"date":"1995-09-15 12:12:12","postman-token":"02e70588-c0c5-493b-bb08-97adcb7938ad","name":"name","host":"127.0.0.1:8080","connection":"keep-alive","id":"123","accept-encoding":"gzip, deflate, br","user-agent":"PostmanRuntime/7.26.8","accept":"*/*"}

#bean2
http://127.0.0.1:8080/headerTransfer/bean2
{"date":811138332000,"id":123,"name":"[name]"}

POST请求（application/x-www-from-urlencoded）

功能描述：POST请求，Content-Type为application/x-www-from-urlencoded，使用： @RequestParam和对象接收参数。

package com.what21.demo.controller;

import com.alibaba.fastjson.JSON;
import com.what21.demo.controller.param.UrlEncodedBodyTransfer;
import org.springframework.beans.propertyeditors.CustomDateEditor;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.WebDataBinder;
import org.springframework.web.bind.annotation.*;
import org.springframework.web.context.request.WebRequest;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Arrays;
import java.util.Date;
import java.util.Map;

@Controller("/urlEncodedBodyTransfer")
@RequestMapping("/urlEncodedBodyTransfer")
public class UrlEncodedBodyTransferController {

    @RequestMapping(path = "/bean1")
    @ResponseBody
    public Object bean1(HttpServletRequest request, HttpServletResponse response) {
        Map<String, String[]> paramsMap = request.getParameterMap();
        if (paramsMap != null) {
            for (String key : paramsMap.keySet()) {
                System.out.println(key + "=" + Arrays.toString(paramsMap.get(key)));
            }
        }
        return JSON.toJSONString(paramsMap);
    }

    @RequestMapping(path = "/bean2")
    @ResponseBody
    public Object bean2(HttpServletRequest request, @RequestParam("id") Integer id, @RequestParam("name") String[] names,
                        @RequestParam("date") String dateStr) {
        UrlEncodedBodyTransfer urlEncodedBodyTransfer = new UrlEncodedBodyTransfer();
        urlEncodedBodyTransfer.setId(id);
        urlEncodedBodyTransfer.setName(Arrays.toString(names));
        try {
            DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
            urlEncodedBodyTransfer.setDate(dateFormat.parse(dateStr));
        } catch (Exception e) {
            e.printStackTrace();
        }
        return JSON.toJSONString(urlEncodedBodyTransfer);
    }

    /**
     * 局部转换
     *
     * @param binder
     * @param request
     */
    @InitBinder
    public void initBinder(WebDataBinder binder, WebRequest request) {
        //转换日期
        DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        // CustomDateEditor为自定义日期编辑器
        binder.registerCustomEditor(Date.class, new CustomDateEditor(dateFormat, true));
    }

    @RequestMapping(path = "/bean3")
    @ResponseBody
    public Object bean3(HttpServletRequest request, @RequestParam("id") Integer id, @RequestParam("name") String[] names,
                        @RequestParam("date") Date date) {
        UrlEncodedBodyTransfer urlEncodedBodyTransfer = new UrlEncodedBodyTransfer();
        urlEncodedBodyTransfer.setId(id);
        urlEncodedBodyTransfer.setName(Arrays.toString(names));
        urlEncodedBodyTransfer.setDate(date);
        return JSON.toJSONString(urlEncodedBodyTransfer);
    }

    @RequestMapping(path = "/bean4")
    @ResponseBody
    public Object bean4(HttpServletRequest request, UrlEncodedBodyTransfer urlEncodedBodyTransfer) {
        System.out.println(">>>>" + request.getHeader("Content-Type"));
        // multipart/form-data; boundary=--------------------------804118925244390549364281
        // application/x-www-form-urlencoded
        return JSON.toJSONString(urlEncodedBodyTransfer);
    }

}

package com.what21.demo.controller.param;

import lombok.Data;

import java.util.Date;

/**
 * application/x-www-from-urlencoded
 */
@Data
public class UrlEncodedBodyTransfer {

    private Integer id;

    private String name;

    private Date date;

}

功能测试：

#bean1
http://127.0.0.1:8080/urlEncodedBodyTransfer/bean1
{"id":["123"],"name":["名字1","名字2"],"date":["1995-09-15 12:12:12"]}

#bean2
http://127.0.0.1:8080/urlEncodedBodyTransfer/bean2
{"date":811138332000,"id":123,"name":"[名字1, 名字2]"}

#bean3
http://127.0.0.1:8080/urlEncodedBodyTransfer/bean3
{"date":811138332000,"id":123,"name":"[名字1, 名字2]"}

#bean4
http://127.0.0.1:8080/urlEncodedBodyTransfer/bean4
{"date":811138332000,"id":123,"name":"名字1,名字2"}


结论：@RequestBody，不支持：application/x-www-form-urlencoded
@RequestMapping(path = "/bean5")
@ResponseBody
public Object bean5(HttpServletRequest request, @RequestBody UrlEncodedBodyTransfer urlEncodedBodyTransfer) {
    System.out.println(">>>>" + request.getHeader("Content-Type"));
    return JSON.toJSONString(urlEncodedBodyTransfer);
}
报错：
Resolved [org.springframework.web.HttpMediaTypeNotSupportedException: Content type 'application/x-www-form-urlencoded;charset=UTF-8' not supported]

POST请求（multipart/form-data）

功能描述：POST请求，Content-Type为multipart/form-data，使用： @RequestParam和对象接收参数。

package com.what21.demo.controller;

import com.alibaba.fastjson.JSON;
import com.what21.demo.controller.param.FormDataTransfer;
import org.springframework.beans.propertyeditors.CustomDateEditor;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.WebDataBinder;
import org.springframework.web.bind.annotation.*;
import org.springframework.web.context.request.WebRequest;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.*;

@Controller("/formDataTransfer")
@RequestMapping("/formDataTransfer")
public class FormDataTransferController {

    @RequestMapping(path = "/bean1")
    @ResponseBody
    public Object bean1(HttpServletRequest request, HttpServletResponse response) {
        Map<String, String[]> paramsMap = request.getParameterMap();
        if (paramsMap != null) {
            for (String key : paramsMap.keySet()) {
                System.out.println(key + "=" + Arrays.toString(paramsMap.get(key)));
            }
        }
        return JSON.toJSONString(paramsMap);
    }

    @RequestMapping(path = "/bean2")
    @ResponseBody
    public Object bean2(HttpServletRequest request, @RequestParam("id") Integer id, @RequestParam("name") String[] names,
                        @RequestParam("date") String dateStr) {
        FormDataTransfer formDataTransfer = new FormDataTransfer();
        formDataTransfer.setId(id);
        formDataTransfer.setName(Arrays.toString(names));
        try {
            DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
            formDataTransfer.setDate(dateFormat.parse(dateStr));
        } catch (Exception e) {
            e.printStackTrace();
        }
        return JSON.toJSONString(formDataTransfer);
    }

    /**
     * 局部转换
     *
     * @param binder
     * @param request
     */
    @InitBinder
    public void initBinder(WebDataBinder binder, WebRequest request) {
        //转换日期
        DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        // CustomDateEditor为自定义日期编辑器
        binder.registerCustomEditor(Date.class, new CustomDateEditor(dateFormat, true));
    }

    @RequestMapping(path = "/bean3")
    @ResponseBody
    public Object bean3(HttpServletRequest request, @RequestParam("id") Integer id, @RequestParam("name") String[] names,
                        @RequestParam("date") Date date) {
        FormDataTransfer formDataTransfer = new FormDataTransfer();
        formDataTransfer.setId(id);
        formDataTransfer.setName(Arrays.toString(names));
        formDataTransfer.setDate(date);
        return JSON.toJSONString(formDataTransfer);
    }

    @RequestMapping(path = "/bean4")
    @ResponseBody
    public Object bean4(HttpServletRequest request, FormDataTransfer formDataTransfer) {
        System.out.println(">>>>" + request.getHeader("Content-Type"));
        // multipart/form-data; boundary=--------------------------804118925244390549364281
        // application/x-www-form-urlencoded
        return JSON.toJSONString(formDataTransfer);
    }

    @RequestMapping(path = "/bean6")
    @ResponseBody
    public Object bean6(HttpServletRequest request, HttpServletResponse response) {
        System.out.println("" + request.getHeader("Content-Type"));
        Map<String, Object> paramsMap = new HashMap<>();
        //
        return JSON.toJSONString(paramsMap);
    }


}

package com.what21.demo.controller.param;

import lombok.Data;

import java.util.Date;

/**
 * multipart/form-data
 */
@Data
public class FormDataTransfer {

    private Integer id;

    private String name;

    private Date date;

}

功能测试：

#bean1
http://127.0.0.1:8080/formDataTransfer/bean1
{"id":["123"],"name":["名字1","名字2"],"date":["1995-09-15 12:12:12"]}

#bean2
http://127.0.0.1:8080/formDataTransfer/bean2
{"date":811138332000,"id":123,"name":"[名字1, 名字2]"}

#bean3
http://127.0.0.1:8080/formDataTransfer/bean3
{"date":811138332000,"id":123,"name":"[名字1, 名字2]"}

#bean4
http://127.0.0.1:8080/formDataTransfer/bean4
{"date":811138332000,"id":123,"name":"名字1,名字2"}


结论：@RequestBody，不支持：multipart/form-data
@RequestMapping(path = "/bean5")
@ResponseBody
public Object bean5(HttpServletRequest request, @RequestBody FormDataTransfer formDataTransfer) {
    System.out.println(">>>>" + request.getHeader("Content-Type"));
    return JSON.toJSONString(formDataTransfer);
}
报错：
Resolved [org.springframework.web.HttpMediaTypeNotSupportedException: Content type 'multipart/form-data;boundary=--------------------------034028183147454180710906;charset=UTF-8' not supported]

POST请求（application/json）

功能描述：POST请求，Content-Type为application/json，使用： @RequestBody接收参数。

package com.what21.demo.controller;

import com.alibaba.fastjson.JSON;
import com.what21.demo.controller.param.JsonBodyTransfer;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.ResponseBody;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;

@Controller("/jsonBodyTransfer")
@RequestMapping("/jsonBodyTransfer")
public class JsonBodyTransferController {

    @RequestMapping(path = "/bean1")
    @ResponseBody
    public Object bean1(HttpServletRequest request, HttpServletResponse response) {
        //
        JsonBodyTransfer jsonBodyTransfer = JSON.parseObject(toJson(request), JsonBodyTransfer.class);
        return jsonBodyTransfer;
    }

    /**
     * @param request
     * @return
     */
    private String toJson(HttpServletRequest request) {
        String result = "";
        try {
            InputStream input = request.getInputStream();
            InputStreamReader reader = new InputStreamReader(input);
            BufferedReader bufferReader = new BufferedReader(reader);
            String line = null;
            StringBuilder sb = new StringBuilder();
            while ((line = bufferReader.readLine()) != null) {
                sb.append(line);
            }
            result = sb.toString();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return result;

    }

    @RequestMapping(path = "/bean2")
    @ResponseBody
    public Object bean2(HttpServletRequest request, @RequestBody JsonBodyTransfer jsonBodyTransfer) {
        return jsonBodyTransfer;
    }

}

package com.what21.demo.controller.param;

import com.alibaba.fastjson.JSON;
import com.fasterxml.jackson.annotation.JsonFormat;
import lombok.Data;

import java.util.Date;

/**
 * application/json
 */
@Data
public class JsonBodyTransfer {

    private Integer id;

    private String name;

    @JsonFormat(pattern="yyyy-MM-dd HH:mm:ss",timezone = "GMT+8")
    private Date date;

    public static void main(String[] args) {
        JsonBodyTransfer jsonBodyTransfer = new JsonBodyTransfer();
        jsonBodyTransfer.setId(1212);
        jsonBodyTransfer.setName("名称");
        jsonBodyTransfer.setDate(new Date());
        System.out.println(JSON.toJSONString(jsonBodyTransfer));
    }

}

功能测试：

#bean1
http://127.0.0.1:8080/jsonBodyTransfer/bean1
---------------------------------------------------------------------
{
    "date":"1995-09-15 12:12:12",
    "id":1212,
    "name":"名称"
}
---------------------------------------------------------------------
{
    "id": 1212,
    "name": "名称",
    "date": "1995-09-15T04:12:12.000+00:00"
}
---------------------------------------------------------------------

#bean2
http://127.0.0.1:8080/jsonBodyTransfer/bean2
---------------------------------------------------------------------
{
    "date":"1995-09-15 12:12:12",
    "id":1212,
    "name":"名称"
}
---------------------------------------------------------------------
{
    "id": 1212,
    "name": "名称",
    "date": "1995-09-15 12:12:12"
}
---------------------------------------------------------------------

POST请求（application/xml）

功能描述：POST请求，Content-Type为application/xml，使用：流接收参数。

package com.what21.demo.controller;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;

import javax.servlet.ServletInputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

@Controller("/xmlBodyTransfer")
@RequestMapping("/xmlBodyTransfer")
public class XmlBodyTransferController {

    @RequestMapping(path = "/bean1")
    @ResponseBody
    public Object bean1(HttpServletRequest request, HttpServletResponse response) {
        System.out.println(">>>>" + request.getHeader("Content-Type"));
        byte[] readBytes = new byte[0];
        try {
            readBytes = readBytes(request);
        } catch (IOException e) {
            e.printStackTrace();
        }
        return new String(readBytes);
    }

    /**
     * @param request
     * @return
     * @throws IOException
     */
    private byte[] readBytes(HttpServletRequest request) throws IOException {
        int len = request.getContentLength();
        ServletInputStream input = request.getInputStream();
        byte[] buffer = new byte[len];
        input.read(buffer, 0, len);
        return buffer;
    }

}

功能测试：

#bean1
http://127.0.0.1:8080/xmlBodyTransfer/bean1
---------------------------------------------------------------------
<root>
    <id>1234</id>
    <name>代码</name>
</root>
---------------------------------------------------------------------
<root>
    <id>1234</id>
    <name>代码</name>
</root>
---------------------------------------------------------------------

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推荐阅读：面试淘宝被Tomcat面到“自闭”，学习这份文档之后“吊打”面试官刷完spring+redis+负载均衡+netty+kafka面试题，再去面试BAT...

2023-09-24 17:40 xiyangw

Python中使用三元运算符简化if-else语句
Python中使用三元运算符简化if-else语句

Python是一种极简主义的编程语言，相比其他编程语言，在多个地方简化了代码的写法，可以让我们用更少的时间更简洁地完成工作。以赋值运算符为例:a=a+b简化...

2023-09-24 17:40 xiyangw

雅思课堂 | 雅思口语写作句型第二讲
雅思课堂 | 雅思口语写作句型第二讲

纯干货，无废话用最少的时间学最制胜的内容！泡图书馆泡不过学霸？碎片时间也能弯道超车！向着雅思8分行动起来吧！雅思口语写作句型1.Ipreferseeing...

2023-09-24 17:39 xiyangw

设计模式(三)——简单的状态模式代替if-else
设计模式(三)——简单的状态模式代替if-else

博主将会针对Java面试题写一组文章，包括J2ee，SQL，主流Web框架，中间件等面试过程中面试官经常问的问题，欢迎大家关注。一起学习，一起成长。前言大多数开...

2023-09-24 17:38 xiyangw

如何优化代码中大量的if/else,switch/case?

前言随着项目的迭代，代码中存在的分支判断可能会越来越多，当里面涉及到的逻辑比较复杂或者分支数量实在是多的难以维护的时候，我们就要考虑下，有办法能让这些代码变得更优雅吗？正文使用枚举这里我们简单的定义一...

优秀程序员早就学会用“状态模式”代替if-else了
优秀程序员早就学会用“状态模式”代替if-else了

2020年已经进入倒计时了，大家立好的flag完成了吗？2020实“鼠”不易，希望2021可以“牛”转乾坤。简介状态模式是行为型设计模式的一种。其设计理念是当对...

2023-09-24 17:37 xiyangw

用Select Case语句对执行多条件进行控制
用Select Case语句对执行多条件进行控制

今日的内容是"VBA之EXCEL应用"的第六章"条件判断语句（If...Then...Else）在VBA中的利用"。这讲是第三节...

2023-09-24 17:37 xiyangw

c#入门教程(四)条件判断if else

条件判断，是编程里常用的判断语句，比如某个代码如果满足条件就执行a代码块否则就执行b代码块。案例1：inti=2*5；if(a>0){执行a代码块}elseif(a<0){执行b代码块...

每日学编程之JAVA(十一)—条件语句(if……else)

一个if语句包含一个布尔表达式和一条或多条语句。如果布尔表达式的值为true，则执行if语句中的代码块，否则执行if语句块后面的代码。if语句后面可以跟else语句，当if语句...

不需要策略模式也能避免满屏if/else

除了使用策略模式以外，还可以使用其他设计模式来避免满屏if/else的问题。以下是一些可能的解决方案：工厂模式：将if/else语句移到工厂类中，由工厂类负责创建对象。这样可以将if/else语句从客...

围绕ifelse与业务逻辑的那些梗
围绕ifelse与业务逻辑的那些梗

ifelse很重要，几乎是程序员编程核心，业务逻辑与规则也通过ifelse体现出来，语句简单但是背后文章很大，先看几则幽默图：1.也许默认使用returnf...

2023-09-24 17:36 xiyangw

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