jar:boot-demo/boot-demo-A/target/boot-demo-A-0.0.1-SNAPSHOT.jar!/BOOT-INF/classes!/a.txt

问题

在java spring boot项目中，idea中运行代码读取resources下的文件可以成功，打成jar包后却报了异常。

源码

controller

package com.example.bootdemo.controller;

import com.example.bootdemo.service.TestService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class TestController {

    @Autowired
    TestService testService;

    @GetMapping("test/get")
    public String get() {
        String result = testService.get("a.txt");
        System.out.println(result);
        return result;
    }


}

service

package com.example.bootdemo.service;

import org.apache.tomcat.util.http.fileupload.IOUtils;
import org.springframework.stereotype.Service;
import org.springframework.util.ResourceUtils;

import java.io.*;


@Service
public class TestService {

    public String get(String path) {
        try {
            return readFile(path);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

    public static String readFile(String path) throws Exception {
        File file = ResourceUtils.getFile("classpath:" + path);
        if (!file.exists()) {
            throw new NullPointerException();
        }
        FileInputStream fis = new FileInputStream(file);
        return readFile(fis);
    }

    private static String readFile(InputStream fis) {
        InputStreamReader isr = null;
        try {
            isr = new InputStreamReader(fis, "UTF-8");
            BufferedReader br = new BufferedReader(isr);
            String line;
            StringBuilder sb = new StringBuilder();
            while ((line = br.readLine()) != null) {
                sb.append(line);
            }
            return sb.toString();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            IOUtils.closeQuietly(isr);
            IOUtils.closeQuietly(fis);
        }
        return null;
    }

}

文件夹

启动idea

在idea中访问接口可以发现能正常访问

达成spring boot 可执行jar包后启动项目访问接口，报异常

经过查找资料，发现a.txt会被打包进可执行jar，所以用
File file = ResourceUtils.getFile(“classpath:” + path);
这种读取文件的方式不能读取文件会报错。

解决方法，修改获取输入流方式

1、 修改读取文件方式通过 org.springframework.core.io.ClassPathResource类读取文件

  public static String readFile(String path) throws Exception {
        ClassPathResource classPathResource = new ClassPathResource(path);
        InputStream is =classPathResource.getInputStream();
        return readFile(is);
    }

2 、通过线程上下文加载器获取资源流

 public static String readFile(String path) throws Exception {
        InputStream is = Thread.currentThread().getContextClassLoader().getResourceAsStream(path);
        return readFile(is);
    }

3、通过某个类的类加载器获取资源流

 public static String readFile(String path) throws Exception {
        InputStream is = TestService.class.getClassLoader().getResourceAsStream(path);
        return readFile(is);
    }