Java tutorial
import java.beans.BeanInfo; import java.beans.IntrospectionException; import java.beans.Introspector; import java.beans.PropertyDescriptor; import java.lang.reflect.InvocationTargetException; import java.lang.reflect.Method; import java.sql.ResultSet; import java.sql.ResultSetMetaData; import java.sql.SQLException; import java.sql.Timestamp; import java.util.ArrayList; import java.util.Arrays; import java.util.HashMap; import java.util.Iterator; import java.util.List; import java.util.Map; /** * <p> * Wraps a <code>ResultSet</code> in an <code>Iterator</code>. This is useful * when you want to present a non-database application layer with domain * neutral data. * </p> * * <p> * This implementation requires the <code>ResultSet.isLast()</code> method * to be implemented. * </p> */ public class ResultSetIterator implements Iterator { /** * The wrapped <code>ResultSet</code>. */ private final ResultSet rs; /** * The processor to use when converting a row into an Object[]. */ private final RowProcessor convert; /** * Constructor for ResultSetIterator. * @param rs Wrap this <code>ResultSet</code> in an <code>Iterator</code>. */ public ResultSetIterator(ResultSet rs) { this(rs, new BasicRowProcessor()); } /** * Constructor for ResultSetIterator. * @param rs Wrap this <code>ResultSet</code> in an <code>Iterator</code>. * @param convert The processor to use when converting a row into an * <code>Object[]</code>. Defaults to a * <code>BasicRowProcessor</code>. */ public ResultSetIterator(ResultSet rs, RowProcessor convert) { this.rs = rs; this.convert = convert; } /** * Returns true if there are more rows in the ResultSet. * @return boolean <code>true</code> if there are more rows * @throws RuntimeException if an SQLException occurs. */ public boolean hasNext() { try { return !rs.isLast(); } catch (SQLException e) { rethrow(e); return false; } } /** * Returns the next row as an <code>Object[]</code>. * @return An <code>Object[]</code> with the same number of elements as * columns in the <code>ResultSet</code>. * @see java.util.Iterator#next() * @throws RuntimeException if an SQLException occurs. */ public Object next() { try { rs.next(); return this.convert.toArray(rs); } catch (SQLException e) { rethrow(e); return null; } } /** * Deletes the current row from the <code>ResultSet</code>. * @see java.util.Iterator#remove() * @throws RuntimeException if an SQLException occurs. */ public void remove() { try { this.rs.deleteRow(); } catch (SQLException e) { rethrow(e); } } /** * Rethrow the SQLException as a RuntimeException. This implementation * creates a new RuntimeException with the SQLException's error message. * @param e SQLException to rethrow * @since DbUtils 1.1 */ protected void rethrow(SQLException e) { throw new RuntimeException(e.getMessage()); } } /** * <code>RowProcessor</code> implementations convert * <code>ResultSet</code> rows into various other objects. Implementations * can extend <code>BasicRowProcessor</code> to protect themselves * from changes to this interface. * * @see BasicRowProcessor */ interface RowProcessor { /** * Create an <code>Object[]</code> from the column values in one * <code>ResultSet</code> row. The <code>ResultSet</code> should be * positioned on a valid row before passing it to this method. * Implementations of this method must not alter the row position of * the <code>ResultSet</code>. * * @param rs ResultSet that supplies the array data * @throws SQLException if a database access error occurs * @return the newly created array */ public Object[] toArray(ResultSet rs) throws SQLException; /** * Create a JavaBean from the column values in one <code>ResultSet</code> * row. The <code>ResultSet</code> should be positioned on a valid row before * passing it to this method. Implementations of this method must not * alter the row position of the <code>ResultSet</code>. * * @param rs ResultSet that supplies the bean data * @param type Class from which to create the bean instance * @throws SQLException if a database access error occurs * @return the newly created bean */ public Object toBean(ResultSet rs, Class type) throws SQLException; /** * Create a <code>List</code> of JavaBeans from the column values in all * <code>ResultSet</code> rows. <code>ResultSet.next()</code> should * <strong>not</strong> be called before passing it to this method. * * @param rs ResultSet that supplies the bean data * @param type Class from which to create the bean instance * @throws SQLException if a database access error occurs * @return A <code>List</code> of beans with the given type in the order * they were returned by the <code>ResultSet</code>. */ public List toBeanList(ResultSet rs, Class type) throws SQLException; /** * Create a <code>Map</code> from the column values in one * <code>ResultSet</code> row. The <code>ResultSet</code> should be * positioned on a valid row before * passing it to this method. Implementations of this method must not * alter the row position of the <code>ResultSet</code>. * * @param rs ResultSet that supplies the map data * @throws SQLException if a database access error occurs * @return the newly created Map */ public Map toMap(ResultSet rs) throws SQLException; } /* * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You 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. */ /** * Basic implementation of the <code>RowProcessor</code> interface. * * <p> * This class is thread-safe. * </p> * * @see RowProcessor */ class BasicRowProcessor implements RowProcessor { /** * The default BeanProcessor instance to use if not supplied in the * constructor. */ private static final BeanProcessor defaultConvert = new BeanProcessor(); /** * The Singleton instance of this class. */ private static final BasicRowProcessor instance = new BasicRowProcessor(); /** * Returns the Singleton instance of this class. * * @return The single instance of this class. * @deprecated Create instances with the constructors instead. This will * be removed after DbUtils 1.1. */ public static BasicRowProcessor instance() { return instance; } /** * Use this to process beans. */ private final BeanProcessor convert; /** * BasicRowProcessor constructor. Bean processing defaults to a * BeanProcessor instance. */ public BasicRowProcessor() { this(defaultConvert); } /** * BasicRowProcessor constructor. * @param convert The BeanProcessor to use when converting columns to * bean properties. * @since DbUtils 1.1 */ public BasicRowProcessor(BeanProcessor convert) { super(); this.convert = convert; } /** * Convert a <code>ResultSet</code> row into an <code>Object[]</code>. * This implementation copies column values into the array in the same * order they're returned from the <code>ResultSet</code>. Array elements * will be set to <code>null</code> if the column was SQL NULL. * * @see org.apache.commons.dbutils.RowProcessor#toArray(java.sql.ResultSet) */ public Object[] toArray(ResultSet rs) throws SQLException { ResultSetMetaData meta = rs.getMetaData(); int cols = meta.getColumnCount(); Object[] result = new Object[cols]; for (int i = 0; i < cols; i++) { result[i] = rs.getObject(i + 1); } return result; } /** * Convert a <code>ResultSet</code> row into a JavaBean. This * implementation delegates to a BeanProcessor instance. * @see org.apache.commons.dbutils.RowProcessor#toBean(java.sql.ResultSet, java.lang.Class) * @see org.apache.commons.dbutils.BeanProcessor#toBean(java.sql.ResultSet, java.lang.Class) */ public Object toBean(ResultSet rs, Class type) throws SQLException { return this.convert.toBean(rs, type); } /** * Convert a <code>ResultSet</code> into a <code>List</code> of JavaBeans. * This implementation delegates to a BeanProcessor instance. * @see org.apache.commons.dbutils.RowProcessor#toBeanList(java.sql.ResultSet, java.lang.Class) * @see org.apache.commons.dbutils.BeanProcessor#toBeanList(java.sql.ResultSet, java.lang.Class) */ public List toBeanList(ResultSet rs, Class type) throws SQLException { return this.convert.toBeanList(rs, type); } /** * Convert a <code>ResultSet</code> row into a <code>Map</code>. This * implementation returns a <code>Map</code> with case insensitive column * names as keys. Calls to <code>map.get("COL")</code> and * <code>map.get("col")</code> return the same value. * @see org.apache.commons.dbutils.RowProcessor#toMap(java.sql.ResultSet) */ public Map toMap(ResultSet rs) throws SQLException { Map result = new CaseInsensitiveHashMap(); ResultSetMetaData rsmd = rs.getMetaData(); int cols = rsmd.getColumnCount(); for (int i = 1; i <= cols; i++) { result.put(rsmd.getColumnName(i), rs.getObject(i)); } return result; } /** * A Map that converts all keys to lowercase Strings for case insensitive * lookups. This is needed for the toMap() implementation because * databases don't consistenly handle the casing of column names. * * <p>The keys are stored as they are given [BUG #DBUTILS-34], so we maintain * an internal mapping from lowercase keys to the real keys in order to * achieve the case insensitive lookup. * * <p>Note: This implementation does not allow <tt>null</tt> * for key, whereas {@link HashMap} does, because of the code: * <pre> * key.toString().toLowerCase() * </pre> */ private static class CaseInsensitiveHashMap extends HashMap { /** * The internal mapping from lowercase keys to the real keys. * * <p> * Any query operation using the key * ({@link #get(Object)}, {@link #containsKey(Object)}) * is done in three steps: * <ul> * <li>convert the parameter key to lower case</li> * <li>get the actual key that corresponds to the lower case key</li> * <li>query the map with the actual key</li> * </ul> * </p> */ private final Map lowerCaseMap = new HashMap(); /** * Required for serialization support. * * @see java.io.Serializable */ private static final long serialVersionUID = 1841673097701957808L; /** * @see java.util.Map#containsKey(java.lang.Object) */ public boolean containsKey(Object key) { Object realKey = lowerCaseMap.get(key.toString().toLowerCase()); return super.containsKey(realKey); // Possible optimisation here: // Since the lowerCaseMap contains a mapping for all the keys, // we could just do this: // return lowerCaseMap.containsKey(key.toString().toLowerCase()); } /** * @see java.util.Map#get(java.lang.Object) */ public Object get(Object key) { Object realKey = lowerCaseMap.get(key.toString().toLowerCase()); return super.get(realKey); } /** * @see java.util.Map#put(java.lang.Object, java.lang.Object) */ public Object put(Object key, Object value) { /* * In order to keep the map and lowerCaseMap synchronized, * we have to remove the old mapping before putting the * new one. Indeed, oldKey and key are not necessaliry equals. * (That's why we call super.remove(oldKey) and not just * super.put(key, value)) */ Object oldKey = lowerCaseMap.put(key.toString().toLowerCase(), key); Object oldValue = super.remove(oldKey); super.put(key, value); return oldValue; } /** * @see java.util.Map#putAll(java.util.Map) */ public void putAll(Map m) { Iterator iter = m.entrySet().iterator(); while (iter.hasNext()) { Map.Entry entry = (Map.Entry) iter.next(); Object key = entry.getKey(); Object value = entry.getValue(); this.put(key, value); } } /** * @see java.util.Map#remove(java.lang.Object) */ public Object remove(Object key) { Object realKey = lowerCaseMap.remove(key.toString().toLowerCase()); return super.remove(realKey); } } } /* * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You 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. */ /** * <p> * <code>BeanProcessor</code> matches column names to bean property names * and converts <code>ResultSet</code> columns into objects for those bean * properties. Subclasses should override the methods in the processing chain * to customize behavior. * </p> * * <p> * This class is thread-safe. * </p> * * @see BasicRowProcessor * * @since DbUtils 1.1 */ class BeanProcessor { /** * Special array value used by <code>mapColumnsToProperties</code> that * indicates there is no bean property that matches a column from a * <code>ResultSet</code>. */ protected static final int PROPERTY_NOT_FOUND = -1; /** * Set a bean's primitive properties to these defaults when SQL NULL * is returned. These are the same as the defaults that ResultSet get* * methods return in the event of a NULL column. */ private static final Map primitiveDefaults = new HashMap(); static { primitiveDefaults.put(Integer.TYPE, new Integer(0)); primitiveDefaults.put(Short.TYPE, new Short((short) 0)); primitiveDefaults.put(Byte.TYPE, new Byte((byte) 0)); primitiveDefaults.put(Float.TYPE, new Float(0)); primitiveDefaults.put(Double.TYPE, new Double(0)); primitiveDefaults.put(Long.TYPE, new Long(0)); primitiveDefaults.put(Boolean.TYPE, Boolean.FALSE); primitiveDefaults.put(Character.TYPE, new Character('\u0000')); } /** * Constructor for BeanProcessor. */ public BeanProcessor() { super(); } /** * Convert a <code>ResultSet</code> row into a JavaBean. This * implementation uses reflection and <code>BeanInfo</code> classes to * match column names to bean property names. Properties are matched to * columns based on several factors: * <br/> * <ol> * <li> * The class has a writable property with the same name as a column. * The name comparison is case insensitive. * </li> * * <li> * The column type can be converted to the property's set method * parameter type with a ResultSet.get* method. If the conversion fails * (ie. the property was an int and the column was a Timestamp) an * SQLException is thrown. * </li> * </ol> * * <p> * Primitive bean properties are set to their defaults when SQL NULL is * returned from the <code>ResultSet</code>. Numeric fields are set to 0 * and booleans are set to false. Object bean properties are set to * <code>null</code> when SQL NULL is returned. This is the same behavior * as the <code>ResultSet</code> get* methods. * </p> * * @param rs ResultSet that supplies the bean data * @param type Class from which to create the bean instance * @throws SQLException if a database access error occurs * @return the newly created bean */ public Object toBean(ResultSet rs, Class type) throws SQLException { PropertyDescriptor[] props = this.propertyDescriptors(type); ResultSetMetaData rsmd = rs.getMetaData(); int[] columnToProperty = this.mapColumnsToProperties(rsmd, props); return this.createBean(rs, type, props, columnToProperty); } /** * Convert a <code>ResultSet</code> into a <code>List</code> of JavaBeans. * This implementation uses reflection and <code>BeanInfo</code> classes to * match column names to bean property names. Properties are matched to * columns based on several factors: * <br/> * <ol> * <li> * The class has a writable property with the same name as a column. * The name comparison is case insensitive. * </li> * * <li> * The column type can be converted to the property's set method * parameter type with a ResultSet.get* method. If the conversion fails * (ie. the property was an int and the column was a Timestamp) an * SQLException is thrown. * </li> * </ol> * * <p> * Primitive bean properties are set to their defaults when SQL NULL is * returned from the <code>ResultSet</code>. Numeric fields are set to 0 * and booleans are set to false. Object bean properties are set to * <code>null</code> when SQL NULL is returned. This is the same behavior * as the <code>ResultSet</code> get* methods. * </p> * * @param rs ResultSet that supplies the bean data * @param type Class from which to create the bean instance * @throws SQLException if a database access error occurs * @return the newly created List of beans */ public List toBeanList(ResultSet rs, Class type) throws SQLException { List results = new ArrayList(); if (!rs.next()) { return results; } PropertyDescriptor[] props = this.propertyDescriptors(type); ResultSetMetaData rsmd = rs.getMetaData(); int[] columnToProperty = this.mapColumnsToProperties(rsmd, props); do { results.add(this.createBean(rs, type, props, columnToProperty)); } while (rs.next()); return results; } /** * Creates a new object and initializes its fields from the ResultSet. * * @param rs The result set. * @param type The bean type (the return type of the object). * @param props The property descriptors. * @param columnToProperty The column indices in the result set. * @return An initialized object. * @throws SQLException if a database error occurs. */ private Object createBean(ResultSet rs, Class type, PropertyDescriptor[] props, int[] columnToProperty) throws SQLException { Object bean = this.newInstance(type); for (int i = 1; i < columnToProperty.length; i++) { if (columnToProperty[i] == PROPERTY_NOT_FOUND) { continue; } PropertyDescriptor prop = props[columnToProperty[i]]; Class propType = prop.getPropertyType(); Object value = this.processColumn(rs, i, propType); if (propType != null && value == null && propType.isPrimitive()) { value = primitiveDefaults.get(propType); } this.callSetter(bean, prop, value); } return bean; } /** * Calls the setter method on the target object for the given property. * If no setter method exists for the property, this method does nothing. * @param target The object to set the property on. * @param prop The property to set. * @param value The value to pass into the setter. * @throws SQLException if an error occurs setting the property. */ private void callSetter(Object target, PropertyDescriptor prop, Object value) throws SQLException { Method setter = prop.getWriteMethod(); if (setter == null) { return; } Class[] params = setter.getParameterTypes(); try { // convert types for some popular ones if (value != null) { if (value instanceof java.util.Date) { if (params[0].getName().equals("java.sql.Date")) { value = new java.sql.Date(((java.util.Date) value).getTime()); } else if (params[0].getName().equals("java.sql.Time")) { value = new java.sql.Time(((java.util.Date) value).getTime()); } else if (params[0].getName().equals("java.sql.Timestamp")) { value = new java.sql.Timestamp(((java.util.Date) value).getTime()); } } } // Don't call setter if the value object isn't the right type if (this.isCompatibleType(value, params[0])) { setter.invoke(target, new Object[] { value }); } else { throw new SQLException("Cannot set " + prop.getName() + ": incompatible types."); } } catch (IllegalArgumentException e) { throw new SQLException("Cannot set " + prop.getName() + ": " + e.getMessage()); } catch (IllegalAccessException e) { throw new SQLException("Cannot set " + prop.getName() + ": " + e.getMessage()); } catch (InvocationTargetException e) { throw new SQLException("Cannot set " + prop.getName() + ": " + e.getMessage()); } } /** * ResultSet.getObject() returns an Integer object for an INT column. The * setter method for the property might take an Integer or a primitive int. * This method returns true if the value can be successfully passed into * the setter method. Remember, Method.invoke() handles the unwrapping * of Integer into an int. * * @param value The value to be passed into the setter method. * @param type The setter's parameter type. * @return boolean True if the value is compatible. */ private boolean isCompatibleType(Object value, Class type) { // Do object check first, then primitives if (value == null || type.isInstance(value)) { return true; } else if (type.equals(Integer.TYPE) && Integer.class.isInstance(value)) { return true; } else if (type.equals(Long.TYPE) && Long.class.isInstance(value)) { return true; } else if (type.equals(Double.TYPE) && Double.class.isInstance(value)) { return true; } else if (type.equals(Float.TYPE) && Float.class.isInstance(value)) { return true; } else if (type.equals(Short.TYPE) && Short.class.isInstance(value)) { return true; } else if (type.equals(Byte.TYPE) && Byte.class.isInstance(value)) { return true; } else if (type.equals(Character.TYPE) && Character.class.isInstance(value)) { return true; } else if (type.equals(Boolean.TYPE) && Boolean.class.isInstance(value)) { return true; } else { return false; } } /** * Factory method that returns a new instance of the given Class. This * is called at the start of the bean creation process and may be * overridden to provide custom behavior like returning a cached bean * instance. * * @param c The Class to create an object from. * @return A newly created object of the Class. * @throws SQLException if creation failed. */ protected Object newInstance(Class c) throws SQLException { try { return c.newInstance(); } catch (InstantiationException e) { throw new SQLException("Cannot create " + c.getName() + ": " + e.getMessage()); } catch (IllegalAccessException e) { throw new SQLException("Cannot create " + c.getName() + ": " + e.getMessage()); } } /** * Returns a PropertyDescriptor[] for the given Class. * * @param c The Class to retrieve PropertyDescriptors for. * @return A PropertyDescriptor[] describing the Class. * @throws SQLException if introspection failed. */ private PropertyDescriptor[] propertyDescriptors(Class c) throws SQLException { // Introspector caches BeanInfo classes for better performance BeanInfo beanInfo = null; try { beanInfo = Introspector.getBeanInfo(c); } catch (IntrospectionException e) { throw new SQLException("Bean introspection failed: " + e.getMessage()); } return beanInfo.getPropertyDescriptors(); } /** * The positions in the returned array represent column numbers. The * values stored at each position represent the index in the * <code>PropertyDescriptor[]</code> for the bean property that matches * the column name. If no bean property was found for a column, the * position is set to <code>PROPERTY_NOT_FOUND</code>. * * @param rsmd The <code>ResultSetMetaData</code> containing column * information. * * @param props The bean property descriptors. * * @throws SQLException if a database access error occurs * * @return An int[] with column index to property index mappings. The 0th * element is meaningless because JDBC column indexing starts at 1. */ protected int[] mapColumnsToProperties(ResultSetMetaData rsmd, PropertyDescriptor[] props) throws SQLException { int cols = rsmd.getColumnCount(); int columnToProperty[] = new int[cols + 1]; Arrays.fill(columnToProperty, PROPERTY_NOT_FOUND); for (int col = 1; col <= cols; col++) { String columnName = rsmd.getColumnName(col); for (int i = 0; i < props.length; i++) { if (columnName.equalsIgnoreCase(props[i].getName())) { columnToProperty[col] = i; break; } } } return columnToProperty; } /** * Convert a <code>ResultSet</code> column into an object. Simple * implementations could just call <code>rs.getObject(index)</code> while * more complex implementations could perform type manipulation to match * the column's type to the bean property type. * * <p> * This implementation calls the appropriate <code>ResultSet</code> getter * method for the given property type to perform the type conversion. If * the property type doesn't match one of the supported * <code>ResultSet</code> types, <code>getObject</code> is called. * </p> * * @param rs The <code>ResultSet</code> currently being processed. It is * positioned on a valid row before being passed into this method. * * @param index The current column index being processed. * * @param propType The bean property type that this column needs to be * converted into. * * @throws SQLException if a database access error occurs * * @return The object from the <code>ResultSet</code> at the given column * index after optional type processing or <code>null</code> if the column * value was SQL NULL. */ protected Object processColumn(ResultSet rs, int index, Class propType) throws SQLException { if (!propType.isPrimitive() && rs.getObject(index) == null) { return null; } if (propType.equals(String.class)) { return rs.getString(index); } else if (propType.equals(Integer.TYPE) || propType.equals(Integer.class)) { return new Integer(rs.getInt(index)); } else if (propType.equals(Boolean.TYPE) || propType.equals(Boolean.class)) { return new Boolean(rs.getBoolean(index)); } else if (propType.equals(Long.TYPE) || propType.equals(Long.class)) { return new Long(rs.getLong(index)); } else if (propType.equals(Double.TYPE) || propType.equals(Double.class)) { return new Double(rs.getDouble(index)); } else if (propType.equals(Float.TYPE) || propType.equals(Float.class)) { return new Float(rs.getFloat(index)); } else if (propType.equals(Short.TYPE) || propType.equals(Short.class)) { return new Short(rs.getShort(index)); } else if (propType.equals(Byte.TYPE) || propType.equals(Byte.class)) { return new Byte(rs.getByte(index)); } else if (propType.equals(Timestamp.class)) { return rs.getTimestamp(index); } else { return rs.getObject(index); } } }