僅當bean作為方法參數存在時，Spring才會自動裝配

Question

我正在使用@ConditionalOnProperty來創建FileCompressor bean：

@Bean
@ConditionalOnProperty(prefix = "file.rollover.sink", name = "compress", matchIfMissing = true)
public FileCompressor fileCompressor() {
    return new DefaultFileCompressor(...);
}

我想僅在FileCompressor bean存在時自動裝配，如果file.rollover.sink.compress=false作為方法參數，則file.rollover.sink.compress=false null 。 但是，如果我嘗試將其定義為：

@Bean
public RolloverTask rolloverTask(final IntervalCalculator intervalCalculator, final @Autowired(required = false) FileCompressor fileCompressor) {
    return new RolloverTask(intervalCalculator, fileCompressor);
}

我收到以下錯誤：

Parameter 1 of method rolloverTask in com.example.FileRolloverSinkConfiguration required a bean of type 'com.example.compressor.FileCompressor' that could not be found.
    - Bean method 'fileCompressor' in 'FileRolloverSinkConfiguration' not loaded because @ConditionalOnProperty (file.rollover.sink.compress) found different value in property 'compress'

如果不存在，我應該對autowire進行哪些更改或傳遞null ？

- 編輯 -

我的解決方案

private FileCompressor fileCompressor;

@Autowired(required = false)
public void setFileCompressor(final FileCompressor fileCompressor) {
    this.fileCompressor = fileCompressor;
}


@Bean
public RolloverTask rolloverTask(final IntervalCalculator intervalCalculator) {
        log.info("Creating a new rollover task with{} a file compressor", fileCompressor == null ? "out" : "");
        return new RolloverTask(intervalCalculator, fileCompressor);
}

@Bean
@ConditionalOnProperty(prefix = "file.rollover.sink", name = "compress", matchIfMissing = true)
public FileCompressor fileCompressor() {
    return new DefaultFileCompressor(...);
}

Answer 1

我認為你可以使用注釋@ConditionalOnBean和@ConditionalOnMissingBean

我沒有嘗試代碼但它應該是這樣的：

@Bean
@ConditionalOnBean(FileCompressor.class)
public RolloverTask rolloverTask(final IntervalCalculator intervalCalculator, final FileCompressor fileCompressor) {
    return new RolloverTask(intervalCalculator, fileCompressor);
}

和

@Bean
@ConditionalOnMissingBean(FileCompressor.class)
public RolloverTask rolloverTask(final IntervalCalculator intervalCalculator) {
    return new RolloverTask(intervalCalculator, null);
}

Answer 2

沒有havingValue = matchIfMissing = true沒有havingValue = 。 因為如果你沒有創建屬性bean，並且你將擁有一個具有任何值的屬性bean將被創建。

你可以用這種方式解決它：

    @Autowired(required = false)
    private FileCompressor fileCompressor;

    @Bean
    public RolloverTask rolloverTaskWithCompressor(final IntervalCalculator intervalCalculator, final FileCompressor fileCompressor) {
        return new RolloverTask(intervalCalculator, fileCompressor);
   }

或者對於兩個版本的RolloverTask都有不同的bean定義：

    @Bean
    @ConditionalOnProperty(prefix = "file.rollover.sink", name = "compress", havingValue = "no", matchIfMissing = false)
    public RolloverTask rolloverTask(IntervalCalculator intervalCalculator) {
        return new RolloverTask(intervalCalculator, null);
    }

    @Bean
    @ConditionalOnProperty(prefix = "file.rollover.sink", name = "compress", havingValue = "yes", matchIfMissing = true)
    public RolloverTask rolloverTaskWithCompressor(final IntervalCalculator intervalCalculator, final FileCompressor fileCompressor) {
        return new RolloverTask(intervalCalculator, fileCompressor);
   }