spring BeanPropertyRowMapper 源码

  • 2022-08-08
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spring BeanPropertyRowMapper 代码

文件路径:/spring-jdbc/src/main/java/org/springframework/jdbc/core/BeanPropertyRowMapper.java

/*
 * Copyright 2002-2022 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.jdbc.core;

import java.beans.PropertyDescriptor;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Locale;
import java.util.Map;
import java.util.Set;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.springframework.beans.BeanUtils;
import org.springframework.beans.BeanWrapper;
import org.springframework.beans.BeanWrapperImpl;
import org.springframework.beans.NotWritablePropertyException;
import org.springframework.beans.TypeConverter;
import org.springframework.beans.TypeMismatchException;
import org.springframework.core.convert.ConversionService;
import org.springframework.core.convert.support.DefaultConversionService;
import org.springframework.dao.DataRetrievalFailureException;
import org.springframework.dao.InvalidDataAccessApiUsageException;
import org.springframework.jdbc.support.JdbcUtils;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.util.ClassUtils;
import org.springframework.util.StringUtils;

/**
 * {@link RowMapper} implementation that converts a row into a new instance
 * of the specified mapped target class. The mapped target class must be a
 * top-level class and it must have a default or no-arg constructor.
 *
 * <p>Column values are mapped based on matching the column name as obtained from result set
 * meta-data to public setters for the corresponding properties. The names are matched either
 * directly or by transforming a name separating the parts with underscores to the same name
 * using "camel" case.
 *
 * <p>Mapping is provided for fields in the target class for many common types, e.g.:
 * String, boolean, Boolean, byte, Byte, short, Short, int, Integer, long, Long,
 * float, Float, double, Double, BigDecimal, {@code java.util.Date}, etc.
 *
 * <p>To facilitate mapping between columns and fields that don't have matching names,
 * try using column aliases in the SQL statement like "select fname as first_name from customer".
 *
 * <p>For 'null' values read from the database, we will attempt to call the setter, but in the case of
 * Java primitives, this causes a TypeMismatchException. This class can be configured (using the
 * primitivesDefaultedForNullValue property) to trap this exception and use the primitives default value.
 * Be aware that if you use the values from the generated bean to update the database the primitive value
 * will have been set to the primitive's default value instead of null.
 *
 * <p>Please note that this class is designed to provide convenience rather than high performance.
 * For best performance, consider using a custom {@link RowMapper} implementation.
 *
 * @author Thomas Risberg
 * @author Juergen Hoeller
 * @since 2.5
 * @param <T> the result type
 * @see DataClassRowMapper
 */
public class BeanPropertyRowMapper<T> implements RowMapper<T> {

	/** Logger available to subclasses. */
	protected final Log logger = LogFactory.getLog(getClass());

	/** The class we are mapping to. */
	@Nullable
	private Class<T> mappedClass;

	/** Whether we're strictly validating. */
	private boolean checkFullyPopulated = false;

	/** Whether we're defaulting primitives when mapping a null value. */
	private boolean primitivesDefaultedForNullValue = false;

	/** ConversionService for binding JDBC values to bean properties. */
	@Nullable
	private ConversionService conversionService = DefaultConversionService.getSharedInstance();

	/** Map of the fields we provide mapping for. */
	@Nullable
	private Map<String, PropertyDescriptor> mappedFields;

	/** Set of bean properties we provide mapping for. */
	@Nullable
	private Set<String> mappedProperties;


	/**
	 * Create a new {@code BeanPropertyRowMapper} for bean-style configuration.
	 * @see #setMappedClass
	 * @see #setCheckFullyPopulated
	 */
	public BeanPropertyRowMapper() {
	}

	/**
	 * Create a new {@code BeanPropertyRowMapper}, accepting unpopulated
	 * properties in the target bean.
	 * @param mappedClass the class that each row should be mapped to
	 */
	public BeanPropertyRowMapper(Class<T> mappedClass) {
		initialize(mappedClass);
	}

	/**
	 * Create a new {@code BeanPropertyRowMapper}.
	 * @param mappedClass the class that each row should be mapped to
	 * @param checkFullyPopulated whether we're strictly validating that
	 * all bean properties have been mapped from corresponding database fields
	 */
	public BeanPropertyRowMapper(Class<T> mappedClass, boolean checkFullyPopulated) {
		initialize(mappedClass);
		this.checkFullyPopulated = checkFullyPopulated;
	}


	/**
	 * Set the class that each row should be mapped to.
	 */
	public void setMappedClass(Class<T> mappedClass) {
		if (this.mappedClass == null) {
			initialize(mappedClass);
		}
		else {
			if (this.mappedClass != mappedClass) {
				throw new InvalidDataAccessApiUsageException("The mapped class can not be reassigned to map to " +
						mappedClass + " since it is already providing mapping for " + this.mappedClass);
			}
		}
	}

	/**
	 * Get the class that we are mapping to.
	 */
	@Nullable
	public final Class<T> getMappedClass() {
		return this.mappedClass;
	}

	/**
	 * Set whether we're strictly validating that all bean properties have been mapped
	 * from corresponding database fields.
	 * <p>Default is {@code false}, accepting unpopulated properties in the target bean.
	 */
	public void setCheckFullyPopulated(boolean checkFullyPopulated) {
		this.checkFullyPopulated = checkFullyPopulated;
	}

	/**
	 * Return whether we're strictly validating that all bean properties have been
	 * mapped from corresponding database fields.
	 */
	public boolean isCheckFullyPopulated() {
		return this.checkFullyPopulated;
	}

	/**
	 * Set whether we're defaulting Java primitives in the case of mapping a null value
	 * from corresponding database fields.
	 * <p>Default is {@code false}, throwing an exception when nulls are mapped to Java primitives.
	 */
	public void setPrimitivesDefaultedForNullValue(boolean primitivesDefaultedForNullValue) {
		this.primitivesDefaultedForNullValue = primitivesDefaultedForNullValue;
	}

	/**
	 * Return whether we're defaulting Java primitives in the case of mapping a null value
	 * from corresponding database fields.
	 */
	public boolean isPrimitivesDefaultedForNullValue() {
		return this.primitivesDefaultedForNullValue;
	}

	/**
	 * Set a {@link ConversionService} for binding JDBC values to bean properties,
	 * or {@code null} for none.
	 * <p>Default is a {@link DefaultConversionService}, as of Spring 4.3. This
	 * provides support for {@code java.time} conversion and other special types.
	 * @since 4.3
	 * @see #initBeanWrapper(BeanWrapper)
	 */
	public void setConversionService(@Nullable ConversionService conversionService) {
		this.conversionService = conversionService;
	}

	/**
	 * Return a {@link ConversionService} for binding JDBC values to bean properties,
	 * or {@code null} if none.
	 * @since 4.3
	 */
	@Nullable
	public ConversionService getConversionService() {
		return this.conversionService;
	}


	/**
	 * Initialize the mapping meta-data for the given class.
	 * @param mappedClass the mapped class
	 */
	protected void initialize(Class<T> mappedClass) {
		this.mappedClass = mappedClass;
		this.mappedFields = new HashMap<>();
		this.mappedProperties = new HashSet<>();

		for (PropertyDescriptor pd : BeanUtils.getPropertyDescriptors(mappedClass)) {
			if (pd.getWriteMethod() != null) {
				String lowerCaseName = lowerCaseName(pd.getName());
				this.mappedFields.put(lowerCaseName, pd);
				String underscoreName = underscoreName(pd.getName());
				if (!lowerCaseName.equals(underscoreName)) {
					this.mappedFields.put(underscoreName, pd);
				}
				this.mappedProperties.add(pd.getName());
			}
		}
	}

	/**
	 * Remove the specified property from the mapped fields.
	 * @param propertyName the property name (as used by property descriptors)
	 * @since 5.3.9
	 */
	protected void suppressProperty(String propertyName) {
		if (this.mappedFields != null) {
			this.mappedFields.remove(lowerCaseName(propertyName));
			this.mappedFields.remove(underscoreName(propertyName));
		}
	}

	/**
	 * Convert the given name to lower case.
	 * By default, conversions will happen within the US locale.
	 * @param name the original name
	 * @return the converted name
	 * @since 4.2
	 */
	protected String lowerCaseName(String name) {
		return name.toLowerCase(Locale.US);
	}

	/**
	 * Convert a name in camelCase to an underscored name in lower case.
	 * Any upper case letters are converted to lower case with a preceding underscore.
	 * @param name the original name
	 * @return the converted name
	 * @since 4.2
	 * @see #lowerCaseName
	 */
	protected String underscoreName(String name) {
		if (!StringUtils.hasLength(name)) {
			return "";
		}

		StringBuilder result = new StringBuilder();
		result.append(Character.toLowerCase(name.charAt(0)));
		for (int i = 1; i < name.length(); i++) {
			char c = name.charAt(i);
			if (Character.isUpperCase(c)) {
				result.append('_').append(Character.toLowerCase(c));
			}
			else {
				result.append(c);
			}
		}
		return result.toString();
	}


	/**
	 * Extract the values for all columns in the current row.
	 * <p>Utilizes public setters and result set meta-data.
	 * @see java.sql.ResultSetMetaData
	 */
	@Override
	public T mapRow(ResultSet rs, int rowNumber) throws SQLException {
		BeanWrapperImpl bw = new BeanWrapperImpl();
		initBeanWrapper(bw);

		T mappedObject = constructMappedInstance(rs, bw);
		bw.setBeanInstance(mappedObject);

		ResultSetMetaData rsmd = rs.getMetaData();
		int columnCount = rsmd.getColumnCount();
		Set<String> populatedProperties = (isCheckFullyPopulated() ? new HashSet<>() : null);

		for (int index = 1; index <= columnCount; index++) {
			String column = JdbcUtils.lookupColumnName(rsmd, index);
			String field = lowerCaseName(StringUtils.delete(column, " "));
			PropertyDescriptor pd = (this.mappedFields != null ? this.mappedFields.get(field) : null);
			if (pd != null) {
				try {
					Object value = getColumnValue(rs, index, pd);
					if (rowNumber == 0 && logger.isDebugEnabled()) {
						logger.debug("Mapping column '" + column + "' to property '" + pd.getName() +
								"' of type '" + ClassUtils.getQualifiedName(pd.getPropertyType()) + "'");
					}
					try {
						bw.setPropertyValue(pd.getName(), value);
					}
					catch (TypeMismatchException ex) {
						if (value == null && this.primitivesDefaultedForNullValue) {
							if (logger.isDebugEnabled()) {
								logger.debug("Intercepted TypeMismatchException for row " + rowNumber +
										" and column '" + column + "' with null value when setting property '" +
										pd.getName() + "' of type '" +
										ClassUtils.getQualifiedName(pd.getPropertyType()) +
										"' on object: " + mappedObject, ex);
							}
						}
						else {
							throw ex;
						}
					}
					if (populatedProperties != null) {
						populatedProperties.add(pd.getName());
					}
				}
				catch (NotWritablePropertyException ex) {
					throw new DataRetrievalFailureException(
							"Unable to map column '" + column + "' to property '" + pd.getName() + "'", ex);
				}
			}
		}

		if (populatedProperties != null && !populatedProperties.equals(this.mappedProperties)) {
			throw new InvalidDataAccessApiUsageException("Given ResultSet does not contain all fields " +
					"necessary to populate object of " + this.mappedClass + ": " + this.mappedProperties);
		}

		return mappedObject;
	}

	/**
	 * Construct an instance of the mapped class for the current row.
	 * @param rs the ResultSet to map (pre-initialized for the current row)
	 * @param tc a TypeConverter with this RowMapper's conversion service
	 * @return a corresponding instance of the mapped class
	 * @throws SQLException if an SQLException is encountered
	 * @since 5.3
	 */
	protected T constructMappedInstance(ResultSet rs, TypeConverter tc) throws SQLException  {
		Assert.state(this.mappedClass != null, "Mapped class was not specified");
		return BeanUtils.instantiateClass(this.mappedClass);
	}

	/**
	 * Initialize the given BeanWrapper to be used for row mapping.
	 * To be called for each row.
	 * <p>The default implementation applies the configured {@link ConversionService},
	 * if any. Can be overridden in subclasses.
	 * @param bw the BeanWrapper to initialize
	 * @see #getConversionService()
	 * @see BeanWrapper#setConversionService
	 */
	protected void initBeanWrapper(BeanWrapper bw) {
		ConversionService cs = getConversionService();
		if (cs != null) {
			bw.setConversionService(cs);
		}
	}

	/**
	 * Retrieve a JDBC object value for the specified column.
	 * <p>The default implementation delegates to
	 * {@link #getColumnValue(ResultSet, int, Class)}.
	 * @param rs is the ResultSet holding the data
	 * @param index is the column index
	 * @param pd the bean property that each result object is expected to match
	 * @return the Object value
	 * @throws SQLException in case of extraction failure
	 * @see #getColumnValue(ResultSet, int, Class)
	 */
	@Nullable
	protected Object getColumnValue(ResultSet rs, int index, PropertyDescriptor pd) throws SQLException {
		return JdbcUtils.getResultSetValue(rs, index, pd.getPropertyType());
	}

	/**
	 * Retrieve a JDBC object value for the specified column.
	 * <p>The default implementation calls
	 * {@link JdbcUtils#getResultSetValue(java.sql.ResultSet, int, Class)}.
	 * Subclasses may override this to check specific value types upfront,
	 * or to post-process values return from {@code getResultSetValue}.
	 * @param rs is the ResultSet holding the data
	 * @param index is the column index
	 * @param paramType the target parameter type
	 * @return the Object value
	 * @throws SQLException in case of extraction failure
	 * @since 5.3
	 * @see org.springframework.jdbc.support.JdbcUtils#getResultSetValue(java.sql.ResultSet, int, Class)
	 */
	@Nullable
	protected Object getColumnValue(ResultSet rs, int index, Class<?> paramType) throws SQLException {
		return JdbcUtils.getResultSetValue(rs, index, paramType);
	}


	/**
	 * Static factory method to create a new {@code BeanPropertyRowMapper}.
	 * @param mappedClass the class that each row should be mapped to
	 * @see #newInstance(Class, ConversionService)
	 */
	public static <T> BeanPropertyRowMapper<T> newInstance(Class<T> mappedClass) {
		return new BeanPropertyRowMapper<>(mappedClass);
	}

	/**
	 * Static factory method to create a new {@code BeanPropertyRowMapper}.
	 * @param mappedClass the class that each row should be mapped to
	 * @param conversionService the {@link ConversionService} for binding
	 * JDBC values to bean properties, or {@code null} for none
	 * @since 5.2.3
	 * @see #newInstance(Class)
	 * @see #setConversionService
	 */
	public static <T> BeanPropertyRowMapper<T> newInstance(
			Class<T> mappedClass, @Nullable ConversionService conversionService) {

		BeanPropertyRowMapper<T> rowMapper = newInstance(mappedClass);
		rowMapper.setConversionService(conversionService);
		return rowMapper;
	}

}

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