spring-batch JpaPagingItemReaderBuilder 源码

spring-batch JpaPagingItemReaderBuilder 代码

文件路径：/spring-batch-infrastructure/src/main/java/org/springframework/batch/item/database/builder/JpaPagingItemReaderBuilder.java

/*
 * Copyright 2017-2021 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.database.builder;

import java.util.Map;
import jakarta.persistence.EntityManagerFactory;

import org.springframework.batch.item.database.JpaPagingItemReader;
import org.springframework.batch.item.database.orm.JpaQueryProvider;
import org.springframework.util.Assert;

/**
 * Creates a fully qualified JpaPagingItemReader.
 *
 * @author Michael Minella
 * @author Glenn Renfro
 * @since 4.0
 */

public class JpaPagingItemReaderBuilder<T> {

	private int pageSize = 10;

	private EntityManagerFactory entityManagerFactory;

	private Map<String, Object> parameterValues;

	private boolean transacted = true;

	private String queryString;

	private JpaQueryProvider queryProvider;

	private boolean saveState = true;

	private String name;

	private int maxItemCount = Integer.MAX_VALUE;

	private int currentItemCount;

	/**
	 * Configure if the state of the
	 * {@link org.springframework.batch.item.ItemStreamSupport} should be persisted within
	 * the {@link org.springframework.batch.item.ExecutionContext} for restart purposes.
	 * @param saveState defaults to true
	 * @return The current instance of the builder.
	 */
	public JpaPagingItemReaderBuilder<T> saveState(boolean saveState) {
		this.saveState = saveState;

		return this;
	}

	/**
	 * The name used to calculate the key within the
	 * {@link org.springframework.batch.item.ExecutionContext}. Required if
	 * {@link #saveState(boolean)} is set to true.
	 * @param name name of the reader instance
	 * @return The current instance of the builder.
	 * @see org.springframework.batch.item.ItemStreamSupport#setName(String)
	 */
	public JpaPagingItemReaderBuilder<T> name(String name) {
		this.name = name;

		return this;
	}

	/**
	 * Configure the max number of items to be read.
	 * @param maxItemCount the max items to be read
	 * @return The current instance of the builder.
	 * @see org.springframework.batch.item.support.AbstractItemCountingItemStreamItemReader#setMaxItemCount(int)
	 */
	public JpaPagingItemReaderBuilder<T> maxItemCount(int maxItemCount) {
		this.maxItemCount = maxItemCount;

		return this;
	}

	/**
	 * Index for the current item. Used on restarts to indicate where to start from.
	 * @param currentItemCount current index
	 * @return this instance for method chaining
	 * @see org.springframework.batch.item.support.AbstractItemCountingItemStreamItemReader#setCurrentItemCount(int)
	 */
	public JpaPagingItemReaderBuilder<T> currentItemCount(int currentItemCount) {
		this.currentItemCount = currentItemCount;

		return this;
	}

	/**
	 * The number of records to request per page/query. Defaults to 10. Must be greater
	 * than zero.
	 * @param pageSize number of items
	 * @return this instance for method chaining
	 * @see JpaPagingItemReader#setPageSize(int)
	 */
	public JpaPagingItemReaderBuilder<T> pageSize(int pageSize) {
		this.pageSize = pageSize;

		return this;
	}

	/**
	 * A map of parameter values to be set on the query. The key of the map is the name of
	 * the parameter to be set with the value being the value to be set.
	 * @param parameterValues map of values
	 * @return this instance for method chaining
	 * @see JpaPagingItemReader#setParameterValues(Map)
	 */
	public JpaPagingItemReaderBuilder<T> parameterValues(Map<String, Object> parameterValues) {
		this.parameterValues = parameterValues;

		return this;
	}

	/**
	 * A query provider. This should be set only if {@link #queryString(String)} have not
	 * been set.
	 * @param queryProvider the query provider
	 * @return this instance for method chaining
	 * @see JpaPagingItemReader#setQueryProvider(JpaQueryProvider)
	 */
	public JpaPagingItemReaderBuilder<T> queryProvider(JpaQueryProvider queryProvider) {
		this.queryProvider = queryProvider;

		return this;
	}

	/**
	 * The HQL query string to execute. This should only be set if
	 * {@link #queryProvider(JpaQueryProvider)} has not been set.
	 * @param queryString the HQL query
	 * @return this instance for method chaining
	 * @see JpaPagingItemReader#setQueryString(String)
	 */
	public JpaPagingItemReaderBuilder<T> queryString(String queryString) {
		this.queryString = queryString;

		return this;
	}

	/**
	 * Indicates if a transaction should be created around the read (true by default). Can
	 * be set to false in cases where JPA implementation doesn't support a particular
	 * transaction, however this may cause object inconsistency in the
	 * EntityManagerFactory.
	 * @param transacted defaults to true
	 * @return this instance for method chaining
	 * @see JpaPagingItemReader#setTransacted(boolean)
	 */
	public JpaPagingItemReaderBuilder<T> transacted(boolean transacted) {
		this.transacted = transacted;

		return this;
	}

	/**
	 * The {@link EntityManagerFactory} to be used for executing the configured
	 * {@link #queryString}.
	 * @param entityManagerFactory {@link EntityManagerFactory} used to create
	 * {@link jakarta.persistence.EntityManager}
	 * @return this instance for method chaining
	 */
	public JpaPagingItemReaderBuilder<T> entityManagerFactory(EntityManagerFactory entityManagerFactory) {
		this.entityManagerFactory = entityManagerFactory;

		return this;
	}

	/**
	 * Returns a fully constructed {@link JpaPagingItemReader}.
	 * @return a new {@link JpaPagingItemReader}
	 */
	public JpaPagingItemReader<T> build() {
		Assert.isTrue(this.pageSize > 0, "pageSize must be greater than zero");
		Assert.notNull(this.entityManagerFactory, "An EntityManagerFactory is required");

		if (this.saveState) {
			Assert.hasText(this.name, "A name is required when saveState is set to true");
		}

		if (this.queryProvider == null) {
			Assert.hasLength(this.queryString, "Query string is required when queryProvider is null");
		}

		JpaPagingItemReader<T> reader = new JpaPagingItemReader<>();

		reader.setQueryString(this.queryString);
		reader.setPageSize(this.pageSize);
		reader.setParameterValues(this.parameterValues);
		reader.setEntityManagerFactory(this.entityManagerFactory);
		reader.setQueryProvider(this.queryProvider);
		reader.setTransacted(this.transacted);
		reader.setCurrentItemCount(this.currentItemCount);
		reader.setMaxItemCount(this.maxItemCount);
		reader.setSaveState(this.saveState);
		reader.setName(this.name);

		return reader;
	}

}

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