Java tutorial
package com.insframework.common.spring.jdbc.mapper; /* * Copyright 2002-2014 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 * * http://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. */ 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.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.NotWritablePropertyException; import org.springframework.beans.PropertyAccessorFactory; import org.springframework.beans.TypeMismatchException; import org.springframework.dao.DataRetrievalFailureException; import org.springframework.dao.InvalidDataAccessApiUsageException; import org.springframework.jdbc.core.RowMapper; import org.springframework.jdbc.support.JdbcUtils; import org.springframework.util.Assert; 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 * metadata 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 databasem, 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 */ /** * ??Object * spring? * @author guom * */ public class BeanPropertyRowMapper<T> implements RowMapper<T> { /** Logger available to subclasses */ protected final Log logger = LogFactory.getLog(getClass()); /** The class we are mapping to */ 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; /** Map of the fields we provide mapping for */ private Map<String, PropertyDescriptor> mappedFields; /** Set of bean properties we provide mapping for */ private Set<String> mappedProperties; /** * Create a new BeanPropertyRowMapper for bean-style configuration. * @see #setMappedClass * @see #setCheckFullyPopulated */ public BeanPropertyRowMapper() { } /** * Create a new BeanPropertyRowMapper, accepting unpopulated properties * in the target bean. * <p>Consider using the {@link #newInstance} factory method instead, * which allows for specifying the mapped type once only. * @param mappedClass the class that each row should be mapped to */ public BeanPropertyRowMapper(Class<T> mappedClass) { initialize(mappedClass); } /** * Create a new 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.equals(mappedClass)) { throw new InvalidDataAccessApiUsageException("The mapped class can not be reassigned to map to " + mappedClass + " since it is already providing mapping for " + this.mappedClass); } } } /** * Initialize the mapping metadata for the given class. * @param mappedClass the mapped class. */ protected void initialize(Class<T> mappedClass) { this.mappedClass = mappedClass; this.mappedFields = new HashMap<String, PropertyDescriptor>(); this.mappedProperties = new HashSet<String>(); PropertyDescriptor[] pds = BeanUtils.getPropertyDescriptors(mappedClass); for (PropertyDescriptor pd : pds) { if (pd.getWriteMethod() != null) { this.mappedFields.put(pd.getName().toLowerCase(), pd); String underscoredName = underscoreName(pd.getName()); if (!pd.getName().toLowerCase().equals(underscoredName)) { this.mappedFields.put(underscoredName, pd); } this.mappedProperties.add(pd.getName()); } } } /** * 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 string containing original name * @return the converted name */ private String underscoreName(String name) { if (!StringUtils.hasLength(name)) { return ""; } StringBuilder result = new StringBuilder(); result.append(name.substring(0, 1).toLowerCase()); for (int i = 1; i < name.length(); i++) { String s = name.substring(i, i + 1); String slc = s.toLowerCase(); if (!s.equals(slc)) { result.append("_").append(slc); } else { result.append(s); } } return result.toString(); } /** * Get the class that we are mapping to. */ 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 primitivesDefaultedForNullValue; } /** * Extract the values for all columns in the current row. * <p>Utilizes public setters and result set metadata. * @see java.sql.ResultSetMetaData */ @Override public T mapRow(ResultSet rs, int rowNumber) throws SQLException { Assert.state(this.mappedClass != null, "Mapped class was not specified"); T mappedObject = BeanUtils.instantiate(this.mappedClass); BeanWrapper bw = PropertyAccessorFactory.forBeanPropertyAccess(mappedObject); initBeanWrapper(bw); ResultSetMetaData rsmd = rs.getMetaData(); int columnCount = rsmd.getColumnCount(); Set<String> populatedProperties = (isCheckFullyPopulated() ? new HashSet<String>() : null); for (int index = 1; index <= columnCount; index++) { String column = JdbcUtils.lookupColumnName(rsmd, index); PropertyDescriptor pd = this.mappedFields.get(column.replaceAll(" ", "").toLowerCase()); if (pd != null) { try { Object value = getColumnValue(rs, index, pd); if (logger.isDebugEnabled() && rowNumber == 0) { logger.debug("Mapping column '" + column + "' to property '" + pd.getName() + "' of type " + pd.getPropertyType()); } try { //add by guom if (pd.getPropertyType() != null && "java.lang.String".equals(pd.getPropertyType().getName())) { if (value != null) { bw.setPropertyValue(pd.getName(), String.valueOf(value)); } else { bw.setPropertyValue(pd.getName(), ""); } } else if (pd.getPropertyType() != null && "double".equals(pd.getPropertyType().getName())) { if (value != null) { bw.setPropertyValue(pd.getName(), value); } else { bw.setPropertyValue(pd.getName(), 0d); } } else { bw.setPropertyValue(pd.getName(), value); } } catch (TypeMismatchException e) { if (value == null && primitivesDefaultedForNullValue) { logger.info("Intercepted TypeMismatchException for row " + rowNumber + " and column '" + column + "' with value " + value + " when setting property '" + pd.getName() + "' of type " + pd.getPropertyType() + " on object: " + mappedObject); } else { throw e; } } 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 class [" + this.mappedClass + "]: " + this.mappedProperties); } return mappedObject; } /** * Initialize the given BeanWrapper to be used for row mapping. * To be called for each row. * <p>The default implementation is empty. Can be overridden in subclasses. * @param bw the BeanWrapper to initialize */ protected void initBeanWrapper(BeanWrapper bw) { } /** * 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 pd the bean property that each result object is expected to match * (or {@code null} if none specified) * @return the Object value * @throws SQLException in case of extraction failure * @see org.springframework.jdbc.support.JdbcUtils#getResultSetValue(java.sql.ResultSet, int, Class) */ protected Object getColumnValue(ResultSet rs, int index, PropertyDescriptor pd) throws SQLException { return JdbcUtils.getResultSetValue(rs, index, pd.getPropertyType()); } /** * Static factory method to create a new BeanPropertyRowMapper * (with the mapped class specified only once). * @param mappedClass the class that each row should be mapped to */ public static <T> BeanPropertyRowMapper<T> newInstance(Class<T> mappedClass) { BeanPropertyRowMapper<T> newInstance = new BeanPropertyRowMapper<T>(); newInstance.setMappedClass(mappedClass); return newInstance; } }