springboot docket 中文乱码

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flybirdfly 2024-09-06 09:29:15

文章标签 乱码 spring boot java 加载 properties文件 文章分类 架构后端开发

问题重现

某不知名springboot小项目，application.properties文件：

custom.param=中文属性值

java代码：

@SpringBootApplication
public class Application {

<span >@Value</span><span >(</span><span >"${custom.param}"</span><span >)</span>
<span >private</span> String param<span >;</span>

<span >public</span> <span >static</span> <span >void</span> <span >main</span><span >(</span>String<span >[</span><span >]</span> args<span >)</span> <span >throws</span> Exception <span >{</span>
    SpringApplication<span >.</span><span >run</span><span >(</span>Application<span >.</span><span >class</span><span >,</span> args<span >)</span><span >;</span>
<span >}</span>

<span >@PostConstruct</span>
<span >public</span> <span >void</span> <span >printText</span><span >(</span><span >)</span> <span >throws</span> UnsupportedEncodingException <span >{</span>
    System<span >.</span>out<span >.</span><span >println</span><span >(</span>param<span >)</span><span >;</span>
    System<span >.</span>out<span >.</span><span >println</span><span >(</span><span >new</span> <span >String</span><span >(</span>param<span >.</span><span >getBytes</span><span >(</span>StandardCharsets<span >.</span>ISO_8859_1<span >)</span><span >,</span> StandardCharsets<span >.</span>UTF_8<span >)</span><span >)</span><span >;</span>
<span >}</span>

控制台输出：

ä¸æ–‡å±žæ€§å€¼
中文属性值

application.properties采用ISO-8859-1加载
自定义test.properties可以设置编码格式
.yml/.yaml默认采用UTF-8加载

application.properties文件加载

正如前文所述读取配置文件时，编码出现了问题。追踪一下spring boot是加载默认配置文件的过程，会发现org.springframework.boot.contex.config.ConfigFileApplicationListener类的loadDocuments()方法，源码如下：

private List<Document> loadDocuments(PropertySourceLoader loader, String name, Resource resource) throws IOException {
    DocumentsCacheKey cacheKey = new DocumentsCacheKey(loader, resource);
    List<Document> documents = this.loadDocumentsCache.get(cacheKey);
    if (documents == null) {
        List<PropertySource<?>> loaded = loader.load(name, resource);
        documents = asDocuments(loaded);
        this.loadDocumentsCache.put(cacheKey, documents);
    }
    return documents;
}

入参loader的类型是PropertySourceLoader，PropertySourceLoader是加载属性文件的接口，其实现有两个类：PropertiesPropertySourceLoader和YamlPropertySourceLoader。loader根据传入参数的实例调用load()方法，此处我们讨论.properties文件，接口声明和properties加载实现如下：

/*********属性文件加载接口**********/
public interface PropertySourceLoader {
    String[] getFileExtensions();
    List<PropertySource<?>> load(String name, Resource resource) throws IOException;
}
/*********properties文件加载实现**********/
public class PropertiesPropertySourceLoader implements PropertySourceLoader {

<span >private</span> <span >static</span> <span >final</span> String XML_FILE_EXTENSION <span >=</span> <span >".xml"</span><span >;</span>

<span >@Override</span>
<span >public</span> String<span >[</span><span >]</span> <span >getFileExtensions</span><span >(</span><span >)</span> <span >{</span>
    <span >return</span> <span >new</span> <span >String</span><span >[</span><span >]</span> <span >{</span> <span >"properties"</span><span >,</span> <span >"xml"</span> <span >}</span><span >;</span>
<span >}</span>

<span >@Override</span>
<span >public</span> List<span ><</span>PropertySource<span ><</span><span >?</span><span >>></span> <span >load</span><span >(</span>String name<span >,</span> Resource resource<span >)</span> <span >throws</span> IOException <span >{</span>
    Map<span ><</span>String<span >,</span> <span >?</span><span >></span> properties <span >=</span> <span >loadProperties</span><span >(</span>resource<span >)</span><span >;</span>
    <span >if</span> <span >(</span>properties<span >.</span><span >isEmpty</span><span >(</span><span >)</span><span >)</span> <span >{</span>
        <span >return</span> Collections<span >.</span><span >emptyList</span><span >(</span><span >)</span><span >;</span>
    <span >}</span>
  <span >return</span> Collections<span >.</span><span >singletonList</span><span >(</span><span >new</span> <span >OriginTrackedMapPropertySource</span><span >(</span>name<span >,</span> properties<span >)</span><span >)</span><span >;</span>

@SuppressWarnings({ “unchecked”, “rawtypes” })
private Map<String, ?> loadProperties(Resource resource) throws IOException {
 String filename = resource.getFilename();
if (filename != null && filename.endsWith(XML_FILE_EXTENSION)) {
return (Map) PropertiesLoaderUtils.loadProperties(resource);
}
return new OriginTrackedPropertiesLoader(resource).load();
}}

通过源码分析PropertiesPropertySourceLoader并不单纯的加载.properties文件，还包含.xml文件（似乎有违单一功能原则，不知道当初这样设计的初衷是啥）。顺着load()方法向下找->loadProperties(Resource)->OriginTrackedPropertiesLoader.load()->OriginTrackedPropertiesLoader.load(boolean)->OriginTrackedPropertiesLoader$CharacterReader(Resource)。
CharacterReader是OriginTrackedPropertiesLoader的内部静态类，而且只有一个构造函数，看看器构造参数就不难发现为啥application.properties是以ISO-8859-1编码加载的了：

private static class CharacterReader implements Closeable {
    // 其他代码省略
    CharacterReader(Resource resource) throws IOException {
      this.reader = new LineNumberReader(new InputStreamReader(
          resource.getInputStream(), StandardCharsets.ISO_8859_1));
    }
    // 其他代码省略
}

也就是说不论application.properties文件被设置为哪种编码格式，最终还是以ISO-8859-1的编码格式进行加载。

yml/yaml默认以UTF-8加载

让我们再看看yml/yaml格式的文件，其加载由PropertySourceLoader接口的另外一个实例YamlPropertySourceLoader实现，即接口方法load()：

List<PropertySource<?>> load(String name, Resource resource) throws IOException;

追一下load()的底层实现，采用org.yaml.snakeyaml.reader.UnicodeReader的实例对yml/ymal文件进行加载，而UnicodeReader实例对文件的初始化方法init()实现如下：

protected void init() throws IOException {
    if (internalIn2 != null)
        return;

Charset encoding<span >;</span>
<span >byte</span> bom<span >[</span><span >]</span> <span >=</span> <span >new</span> <span >byte</span><span >[</span>BOM_SIZE<span >]</span><span >;</span>
<span >int</span> n<span >,</span> unread<span >;</span>
n <span >=</span> internalIn<span >.</span><span >read</span><span >(</span>bom<span >,</span> <span class="token number">0</span><span >,</span> bom<span >.</span>length<span >)</span><span >;</span>

<span >if</span> <span >(</span><span >(</span>bom<span >[</span><span class="token number">0</span><span >]</span> <span >==</span> <span >(</span><span >byte</span><span >)</span> <span class="token number">0xEF</span><span >)</span> <span >&&</span> <span >(</span>bom<span >[</span><span class="token number">1</span><span >]</span> <span >==</span> <span >(</span><span >byte</span><span >)</span> <span class="token number">0xBB</span><span >)</span> <span >&&</span> <span >(</span>bom<span >[</span><span class="token number">2</span><span >]</span> <span >==</span> <span >(</span><span >byte</span><span >)</span> <span class="token number">0xBF</span><span >)</span><span >)</span> <span >{</span>
    encoding <span >=</span> UTF8<span >;</span>
    unread <span >=</span> n <span >-</span> <span class="token number">3</span><span >;</span>
<span >}</span> <span >else</span> <span >if</span> <span >(</span><span >(</span>bom<span >[</span><span class="token number">0</span><span >]</span> <span >==</span> <span >(</span><span >byte</span><span >)</span> <span class="token number">0xFE</span><span >)</span> <span >&&</span> <span >(</span>bom<span >[</span><span class="token number">1</span><span >]</span> <span >==</span> <span >(</span><span >byte</span><span >)</span> <span class="token number">0xFF</span><span >)</span><span >)</span> <span >{</span>
    encoding <span >=</span> UTF16BE<span >;</span>
    unread <span >=</span> n <span >-</span> <span class="token number">2</span><span >;</span>
<span >}</span> <span >else</span> <span >if</span> <span >(</span><span >(</span>bom<span >[</span><span class="token number">0</span><span >]</span> <span >==</span> <span >(</span><span >byte</span><span >)</span> <span class="token number">0xFF</span><span >)</span> <span >&&</span> <span >(</span>bom<span >[</span><span class="token number">1</span><span >]</span> <span >==</span> <span >(</span><span >byte</span><span >)</span> <span class="token number">0xFE</span><span >)</span><span >)</span> <span >{</span>
    encoding <span >=</span> UTF16LE<span >;</span>
    unread <span >=</span> n <span >-</span> <span class="token number">2</span><span >;</span>
<span >}</span> <span >else</span> <span >{</span>
    <span >// Unicode BOM mark not found, unread all bytes</span>
    encoding <span >=</span> UTF8<span >;</span>
    unread <span >=</span> n<span >;</span>
<span >}</span>

<span >if</span> <span >(</span>unread <span >></span> <span class="token number">0</span><span >)</span>
    internalIn<span >.</span><span >unread</span><span >(</span>bom<span >,</span> <span >(</span>n <span >-</span> unread<span >)</span><span >,</span> unread<span >)</span><span >;</span>

<span >// Use given encoding</span>
CharsetDecoder decoder <span >=</span> encoding<span >.</span><span >newDecoder</span><span >(</span><span >)</span><span >.</span><span >onUnmappableCharacter</span><span >(</span>
        CodingErrorAction<span >.</span>REPORT<span >)</span><span >;</span>
internalIn2 <span >=</span> <span >new</span> <span >InputStreamReader</span><span >(</span>internalIn<span >,</span> decoder<span >)</span><span >;</span>

每次调用read()读文件时都会调用init()方法进行初始化，也就是这个时候确定文件的编码格式。首先读取BOM（Byte Order Mark）文件头信息，如果头信息中有UTF8/UTF16BE/UTF16LE就采用对应的编码，没有或者不是则采用UTF8编码。

自定义test.properties文件编码

采用@PropertySource(value=“classpath:test.properties”, encoding=“UTF-8”)方式读取配置文件可按照UTF-8的方式读取编码，而不是ISO-8859-1。@PropertySource配置的加载文件由ConfigurationClassParser.processPropertySource()进行解析，EncodedResource类决定最后由哪种编码格式加载文件，其方法如下：

public Reader getReader() throws IOException {
    if (this.charset != null) {
      return new InputStreamReader(this.resource.getInputStream(), this.charset);
    }
    else if (this.encoding != null) {
      return new InputStreamReader(this.resource.getInputStream(), this.encoding);
    }
    else {
      return new InputStreamReader(this.resource.getInputStream());
    }
  }

所以，虽然都是.properties文件，但是编码格式却是不一样的。

解决方案

自定义配置文件
使用yml/yaml配置文件
IDE/插件预编码

自定义配置文件

通过@PropertySource(value=“classpath:my.properties”, encoding=“UTF-8”)注解配置自定义文件，注意文件名不能是springboot默认的application.properties文件名称。

使用yml/yaml配置文件

将yml/yaml文件设置为UTF-8的编码格式，springboot读该文件即采用UTF-8编码。

IDE/插件预编码

采用编译器或者插件将配置文件预编码。这种方法我没试过，但是想想也知道这是很反人类的。如果有人感兴趣的话，可以参考一下[这篇博客最后一部分IDEA/eclipse的修改操作]¹。

总结

在配置application.properties时，都是开发比较重要的参数，尽量使用英文，业务相关的中文配置还是不要放到这里。

‘Spring Boot自定义属性以及乱码问题’ ↩︎

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问题重现

某不知名springboot小项目，application.properties文件：

custom.param=中文属性值

java代码：

@SpringBootApplication
public class Application {

<span >@Value</span><span >(</span><span >"${custom.param}"</span><span >)</span>
<span >private</span> String param<span >;</span>

<span >public</span> <span >static</span> <span >void</span> <span >main</span><span >(</span>String<span >[</span><span >]</span> args<span >)</span> <span >throws</span> Exception <span >{</span>
    SpringApplication<span >.</span><span >run</span><span >(</span>Application<span >.</span><span >class</span><span >,</span> args<span >)</span><span >;</span>
<span >}</span>

<span >@PostConstruct</span>
<span >public</span> <span >void</span> <span >printText</span><span >(</span><span >)</span> <span >throws</span> UnsupportedEncodingException <span >{</span>
    System<span >.</span>out<span >.</span><span >println</span><span >(</span>param<span >)</span><span >;</span>
    System<span >.</span>out<span >.</span><span >println</span><span >(</span><span >new</span> <span >String</span><span >(</span>param<span >.</span><span >getBytes</span><span >(</span>StandardCharsets<span >.</span>ISO_8859_1<span >)</span><span >,</span> StandardCharsets<span >.</span>UTF_8<span >)</span><span >)</span><span >;</span>
<span >}</span>

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