How springboot reads files under resources

Many times in the project, we need to read custom configuration files. No matter how we write the local development tools, it is successful, but when we deploy it to the service, there will be problems.

Exception BOOT-INF/classes !/config.xml (The file name, directory name or volume label syntax is incorrect.) There are exclamation marks and the like in the path

After understanding it, springboot typed jar is a file, that is, a compression package, There is no way to read the path in the compressed file, So to solve this problem and understand the principle of reading the configuration file, just get the file stream directly.

#1. Use the path within the project to read, which can only be used in development tools and cannot be read after deployment. (Not universal)

Similar to: src/main/resources/default.xml

File file = new File("src/main/resources/default.xml" );

    @Test
    public void testReadFile2() throws IOException {
        File file = new File("src/main/resources/default.xml");
        FileInputStream fis = new FileInputStream(file);
        InputStreamReader isr = new InputStreamReader(fis);
        BufferedReader br = new BufferedReader(isr);
        String data = null;
        while((data = br.readLine()) != null) {
            System.out.println(data);
        }
        
        br.close();
        isr.close();
        fis.close();
    }

2. Use org.springframework.util.ResourceUtils to read. Unable to read in linux environment. (Not universal)

File file = ResourceUtils.getFile("classpath:default.xml");
FileInputStream fis = new FileInputStream(file);

    @Test
    public void testReadFile3() throws IOException {
        File file = ResourceUtils.getFile("classpath:default.xml");
        FileInputStream fis = new FileInputStream(file);
        InputStreamReader isr = new InputStreamReader(fis);
        BufferedReader br = new BufferedReader(isr);
        String data = null;
        while((data = br.readLine()) != null) {
            System.out.println(data);
        }
        
        br.close();
        isr.close();
        fis.close();
    }

3. Using org.springframework.core.io.ClassPathResource, it can be read in various environments. (General)

Resource resource = new ClassPathResource("resource.properties");
InputStream is = resource.getInputStream();

    @Test
    public void testReadFile() throws IOException {
//        ClassPathResource classPathResource = new ClassPathResource("default.xml");
        Resource resource = new ClassPathResource("default.xml");
        InputStream is = resource.getInputStream();
        InputStreamReader isr = new InputStreamReader(is);
        BufferedReader br = new BufferedReader(isr);
        String data = null;
        while((data = br.readLine()) != null) {
            System.out.println(data);
        }
        
        br.close();
        isr.close();
        is.close();
    }

4. Combine with spring annotations and use the annotations of the org.springframework.core.io.ResourceLoader; class. (General)

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
 
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.core.io.Resource;
import org.springframework.core.io.ResourceLoader;
import org.springframework.test.context.junit4.SpringRunner;
 
@RunWith(SpringRunner.class)
@SpringBootTest
public class ApplicationTests {
 
    @Autowired
    ResourceLoader resourceLoader;
    
    
    @Test
    public void testReaderFile() throws IOException {
        Resource resource = resourceLoader.getResource("classpath:default.xml");
        InputStream is = resource.getInputStream();
        InputStreamReader isr = new InputStreamReader(is);
        BufferedReader br = new BufferedReader(isr);
        String data = null;
        while((data = br.readLine()) != null) {
            System.out.println(data);
        }
        
        br.close();
        isr.close();
        is.close();
    }
}

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