【SpringBoot】四种读取 Spring Boot 项目中 jar 包中的 resources 目录下的文件

在 Spring Boot 项目中，你可以使用 ResourceLoader 接口、Resource 抽象类、ClassPathResource 类或 InputStream 来读取位于 resources 目录下的文件。以下是四种方法的示例代码：

1. 使用 ResourceLoader 接口：

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.core.io.Resource;
import org.springframework.core.io.ResourceLoader;
import org.springframework.stereotype.Service;
 
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
 
@Service
public class ResourceService {
 
    @Autowired
    private ResourceLoader resourceLoader;
 
    public String readFileFromResources(String fileName) throws IOException {
        Resource resource = resourceLoader.getResource("classpath:" + fileName);
        InputStream inputStream = resource.getInputStream();
        try (BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream))) {
            return reader.lines().reduce((acc, current) -> acc + "\n" + current).orElse("");
        }
    }
}

2. 使用 Resource 抽象类：

import org.springframework.core.io.Resource;
import org.springframework.core.io.ClassPathResource;
import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.IOException;
 
public class ResourceService {
 
    public String readFileFromResources(String fileName) throws IOException {
        Resource resource = new ClassPathResource(fileName);
        InputStream inputStream = resource.getInputStream();
        try (BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream))) {
            return reader.lines().reduce((acc, current) -> acc + "\n" + current).orElse("");
        }
    }
}

3. 使用 ClassPathResource 类：

import org.springframework.core.io.ClassPathResource;
import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.IOException;
 
public class ResourceService {
 
    public String readFileFromResources(String fileName) throws IOException {
        ClassPathResource classPathResource = new ClassPathResource(fileName);
        InputStream inputStream = classPathResource.getInputStream();
        try (BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream))) {
            return reader.lines().reduce((acc, current) -> acc + "\