java - Spring 批 : Writing column names as first line in flat file

Question

我想创建一个具有以下格式的平面文件:

Col1Name;Col2Name;Col3Name
one;23;20120912
two;28;20120712

如上所示，平面文件中的第一行是列名。

如何通过header回调来实现？

我看到如果输入文件是上述格式，则有一个选项可以忽略第一行:

<property name="firstLineIsHeader" value="true"/>

此外，这 Jira Issue表示我想要的已实现并关闭。但是，我找不到任何将第一行写为列名的示例。

<beans:bean id="MyFileItemWriter" class="com.nik.MyFileItemWriter" scope="step">
    <beans:property name="delegate">
        <beans:bean class="org.springframework.batch.item.file.FlatFileItemWriter">
            <beans:property name="resource" value="file:MYFILE.dat" /> 

            <beans:property name="lineAggregator">
                <beans:bean class="org.springframework.batch.item.file.transform.DelimitedLineAggregator">
                    <beans:property name="delimiter" value=";" />
                    <beans:property name="fieldExtractor">
                        <beans:bean class="org.springframework.batch.item.file.transform.BeanWrapperFieldExtractor">
                            <beans:property name="names" value="Col1Name, Col2Name, Col3Name" />
                        </beans:bean>
                    </beans:property>
                </beans:bean>
            </beans:property>
            <beans:property name="headerCallback" ref="MyFileItemWriter" />
        </beans:bean>
    </beans:property>
</beans:bean>

我的 Item Writer 如下所示:

public class MyFileItemWriter implements ItemWriter<MyBean>, FlatFileHeaderCallback, ItemStream{

private FlatFileItemWriter<MyBean> delegate;    

 public void setDelegate(final FlatFileItemWriter<MyBean> delegate) {
        this.delegate = delegate;
    }

public void writeHeader(Writer writer) throws IOException {


}

public void write(List<? extends MyBean> items) throws Exception {
    this.delegate.write(items);

}

public void close() throws ItemStreamException {
     this.delegate.close();

}

public void open(ExecutionContext arg0) throws ItemStreamException {
     this.delegate.open(arg0);

}

public void update(ExecutionContext arg0) throws ItemStreamException {
     this.delegate.update(arg0);        
}

}

感谢阅读!

Answer 1

创建一个扩展 FlatFileItemWriter 并仅实现构造函数的自定义类:

public class MyFlatFileWriter extends FlatFileItemWriter {

    public MyFlatFileWriter (){
        super.setHeaderCallback(new FlatFileHeaderCallback() {

            public void writeHeader(Writer writer) throws IOException {
                writer.write("Col1Name,Col2Name,Col3Name");

            }
        });
    }

然后在bean配置类属性中使用这个类