spring-batch ExtractorLineAggregator 源码
spring-batch ExtractorLineAggregator 代码
文件路径：/spring-batch-infrastructure/src/main/java/org/springframework/batch/item/file/transform/ExtractorLineAggregator.java
/*
* Copyright 2006-2007 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* https://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.springframework.batch.item.file.transform;
import org.springframework.util.Assert;
/**
* An abstract {@link LineAggregator} implementation that utilizes a
* {@link FieldExtractor} to convert the incoming object to an array of its parts.
* Extending classes must decide how those parts will be aggregated together.
*
* @author Dan Garrette
* @since 2.0
*/
public abstract class ExtractorLineAggregator<T> implements LineAggregator<T> {
private FieldExtractor<T> fieldExtractor = new PassThroughFieldExtractor<>();
/**
* Public setter for the field extractor responsible for splitting an input object up
* into an array of objects. Defaults to {@link PassThroughFieldExtractor}.
* @param fieldExtractor The field extractor to set
*/
public void setFieldExtractor(FieldExtractor<T> fieldExtractor) {
this.fieldExtractor = fieldExtractor;
}
/**
* Extract fields from the given item using the {@link FieldExtractor} and then
* aggregate them. Any null field returned by the extractor will be replaced by an
* empty String. Null items are not allowed.
*
* @see org.springframework.batch.item.file.transform.LineAggregator#aggregate(java.lang.Object)
*/
@Override
public String aggregate(T item) {
Assert.notNull(item, "Item is required");
Object[] fields = this.fieldExtractor.extract(item);
//
// Replace nulls with empty strings
//
Object[] args = new Object[fields.length];
for (int i = 0; i < fields.length; i++) {
if (fields[i] == null) {
args[i] = "";
}
else {
args[i] = fields[i];
}
}
return this.doAggregate(args);
}
/**
* Aggregate provided fields into single String.
* @param fields An array of the fields that must be aggregated
* @return aggregated string
*/
protected abstract String doAggregate(Object[] fields);
}
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