Java tutorial
/* * Copyright (c) 2003, 2019, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package javax.sql.rowset.serial; import java.sql.*; import java.io.*; import java.util.Map; import java.net.URL; import java.util.Arrays; /** * A serialized version of an <code>Array</code> * object, which is the mapping in the Java programming language of an SQL * <code>ARRAY</code> value. * <P> * The <code>SerialArray</code> class provides a constructor for creating * a <code>SerialArray</code> instance from an <code>Array</code> object, * methods for getting the base type and the SQL name for the base type, and * methods for copying all or part of a <code>SerialArray</code> object. * <P> * * Note: In order for this class to function correctly, a connection to the * data source * must be available in order for the SQL <code>Array</code> object to be * materialized (have all of its elements brought to the client server) * if necessary. At this time, logical pointers to the data in the data source, * such as locators, are not currently supported. * * <h2> Thread safety </h2> * * A SerialArray is not safe for use by multiple concurrent threads. If a * SerialArray is to be used by more than one thread then access to the * SerialArray should be controlled by appropriate synchronization. * * @since 1.5 */ public class SerialArray implements Array, Serializable, Cloneable { /** * A serialized array in which each element is an <code>Object</code> * in the Java programming language that represents an element * in the SQL <code>ARRAY</code> value. * @serial */ private Object[] elements; /** * The SQL type of the elements in this <code>SerialArray</code> object. The * type is expressed as one of the constants from the class * <code>java.sql.Types</code>. * @serial */ private int baseType; /** * The type name used by the DBMS for the elements in the SQL <code>ARRAY</code> * value that this <code>SerialArray</code> object represents. * @serial */ private String baseTypeName; /** * The number of elements in this <code>SerialArray</code> object, which * is also the number of elements in the SQL <code>ARRAY</code> value * that this <code>SerialArray</code> object represents. * @serial */ private int len; /** * Constructs a new <code>SerialArray</code> object from the given * <code>Array</code> object, using the given type map for the custom * mapping of each element when the elements are SQL UDTs. * <P> * This method does custom mapping if the array elements are a UDT * and the given type map has an entry for that UDT. * Custom mapping is recursive, * meaning that if, for instance, an element of an SQL structured type * is an SQL structured type that itself has an element that is an SQL * structured type, each structured type that has a custom mapping will be * mapped according to the given type map. * <P> * The new <code>SerialArray</code> * object contains the same elements as the <code>Array</code> object * from which it is built, except when the base type is the SQL type * <code>STRUCT</code>, <code>ARRAY</code>, <code>BLOB</code>, * <code>CLOB</code>, <code>DATALINK</code> or <code>JAVA_OBJECT</code>. * In this case, each element in the new * <code>SerialArray</code> object is the appropriate serialized form, * that is, a <code>SerialStruct</code>, <code>SerialArray</code>, * <code>SerialBlob</code>, <code>SerialClob</code>, * <code>SerialDatalink</code>, or <code>SerialJavaObject</code> object. * <P> * Note: (1) The <code>Array</code> object from which a <code>SerialArray</code> * object is created must have materialized the SQL <code>ARRAY</code> value's * data on the client before it is passed to the constructor. Otherwise, * the new <code>SerialArray</code> object will contain no data. * <p> * Note: (2) If the <code>Array</code> contains <code>java.sql.Types.JAVA_OBJECT</code> * types, the <code>SerialJavaObject</code> constructor is called where checks * are made to ensure this object is serializable. * <p> * Note: (3) The <code>Array</code> object supplied to this constructor cannot * return <code>null</code> for any <code>Array.getArray()</code> methods. * <code>SerialArray</code> cannot serialize null array values. * * * @param array the <code>Array</code> object to be serialized * @param map a <code>java.util.Map</code> object in which * each entry consists of 1) a <code>String</code> object * giving the fully qualified name of a UDT (an SQL structured type or * distinct type) and 2) the * <code>Class</code> object for the <code>SQLData</code> implementation * that defines how the UDT is to be mapped. The <i>map</i> * parameter does not have any effect for <code>Blob</code>, * <code>Clob</code>, <code>DATALINK</code>, or * <code>JAVA_OBJECT</code> types. * @throws SerialException if an error occurs serializing the * <code>Array</code> object * @throws SQLException if a database access error occurs or if the * <i>array</i> or the <i>map</i> values are <code>null</code> */ public SerialArray(Array array, Map<String, Class<?>> map) throws SerialException, SQLException { if ((array == null) || (map == null)) { throw new SQLException("Cannot instantiate a SerialArray " + "object with null parameters"); } if ((elements = (Object[]) array.getArray()) == null) { throw new SQLException("Invalid Array object. Calls to Array.getArray() " + "return null value which cannot be serialized"); } elements = (Object[]) array.getArray(map); baseType = array.getBaseType(); baseTypeName = array.getBaseTypeName(); len = elements.length; switch (baseType) { case java.sql.Types.STRUCT: for (int i = 0; i < len; i++) { elements[i] = new SerialStruct((Struct) elements[i], map); } break; case java.sql.Types.ARRAY: for (int i = 0; i < len; i++) { elements[i] = new SerialArray((Array) elements[i], map); } break; case java.sql.Types.BLOB: for (int i = 0; i < len; i++) { elements[i] = new SerialBlob((Blob) elements[i]); } break; case java.sql.Types.CLOB: for (int i = 0; i < len; i++) { elements[i] = new SerialClob((Clob) elements[i]); } break; case java.sql.Types.DATALINK: for (int i = 0; i < len; i++) { elements[i] = new SerialDatalink((URL) elements[i]); } break; case java.sql.Types.JAVA_OBJECT: for (int i = 0; i < len; i++) { elements[i] = new SerialJavaObject(elements[i]); } } } /** * This method frees the {@code SerialArray} object and releases the * resources that it holds. The object is invalid once the {@code free} * method is called. <p> If {@code free} is called multiple times, the * subsequent calls to {@code free} are treated as a no-op. </P> * * @throws SQLException if an error occurs releasing the SerialArray's resources * @since 1.6 */ public void free() throws SQLException { if (elements != null) { elements = null; baseTypeName = null; } } /** * Constructs a new <code>SerialArray</code> object from the given * <code>Array</code> object. * <P> * This constructor does not do custom mapping. If the base type of the array * is an SQL structured type and custom mapping is desired, the constructor * <code>SerialArray(Array array, Map map)</code> should be used. * <P> * The new <code>SerialArray</code> * object contains the same elements as the <code>Array</code> object * from which it is built, except when the base type is the SQL type * <code>BLOB</code>, * <code>CLOB</code>, <code>DATALINK</code> or <code>JAVA_OBJECT</code>. * In this case, each element in the new * <code>SerialArray</code> object is the appropriate serialized form, * that is, a <code>SerialBlob</code>, <code>SerialClob</code>, * <code>SerialDatalink</code>, or <code>SerialJavaObject</code> object. * <P> * Note: (1) The <code>Array</code> object from which a <code>SerialArray</code> * object is created must have materialized the SQL <code>ARRAY</code> value's * data on the client before it is passed to the constructor. Otherwise, * the new <code>SerialArray</code> object will contain no data. * <p> * Note: (2) The <code>Array</code> object supplied to this constructor cannot * return <code>null</code> for any <code>Array.getArray()</code> methods. * <code>SerialArray</code> cannot serialize <code>null</code> array values. * * @param array the <code>Array</code> object to be serialized * @throws SerialException if an error occurs serializing the * <code>Array</code> object * @throws SQLException if a database access error occurs or the * <i>array</i> parameter is <code>null</code>. */ public SerialArray(Array array) throws SerialException, SQLException { if (array == null) { throw new SQLException("Cannot instantiate a SerialArray " + "object with a null Array object"); } if ((elements = (Object[]) array.getArray()) == null) { throw new SQLException("Invalid Array object. Calls to Array.getArray() " + "return null value which cannot be serialized"); } //elements = (Object[])array.getArray(); baseType = array.getBaseType(); baseTypeName = array.getBaseTypeName(); len = elements.length; switch (baseType) { case java.sql.Types.BLOB: for (int i = 0; i < len; i++) { elements[i] = new SerialBlob((Blob) elements[i]); } break; case java.sql.Types.CLOB: for (int i = 0; i < len; i++) { elements[i] = new SerialClob((Clob) elements[i]); } break; case java.sql.Types.DATALINK: for (int i = 0; i < len; i++) { elements[i] = new SerialDatalink((URL) elements[i]); } break; case java.sql.Types.JAVA_OBJECT: for (int i = 0; i < len; i++) { elements[i] = new SerialJavaObject(elements[i]); } break; } } /** * Returns a new array that is a copy of this <code>SerialArray</code> * object. * * @return a copy of this <code>SerialArray</code> object as an * <code>Object</code> in the Java programming language * @throws SerialException if an error occurs; * if {@code free} had previously been called on this object */ public Object getArray() throws SerialException { isValid(); Object dst = new Object[len]; System.arraycopy((Object) elements, 0, dst, 0, len); return dst; } /** * Returns a new array that is a copy of this <code>SerialArray</code> * object, using the given type map for the custom * mapping of each element when the elements are SQL UDTs. * <P> * This method does custom mapping if the array elements are a UDT * and the given type map has an entry for that UDT. * Custom mapping is recursive, * meaning that if, for instance, an element of an SQL structured type * is an SQL structured type that itself has an element that is an SQL * structured type, each structured type that has a custom mapping will be * mapped according to the given type map. * * @param map a <code>java.util.Map</code> object in which * each entry consists of 1) a <code>String</code> object * giving the fully qualified name of a UDT and 2) the * <code>Class</code> object for the <code>SQLData</code> implementation * that defines how the UDT is to be mapped * @return a copy of this <code>SerialArray</code> object as an * <code>Object</code> in the Java programming language * @throws SerialException if an error occurs; * if {@code free} had previously been called on this object */ public Object getArray(Map<String, Class<?>> map) throws SerialException { isValid(); Object dst[] = new Object[len]; System.arraycopy((Object) elements, 0, dst, 0, len); return dst; } /** * Returns a new array that is a copy of a slice * of this <code>SerialArray</code> object, starting with the * element at the given index and containing the given number * of consecutive elements. * * @param index the index into this <code>SerialArray</code> object * of the first element to be copied; * the index of the first element is <code>0</code> * @param count the number of consecutive elements to be copied, starting * at the given index * @return a copy of the designated elements in this <code>SerialArray</code> * object as an <code>Object</code> in the Java programming language * @throws SerialException if an error occurs; * if {@code free} had previously been called on this object */ public Object getArray(long index, int count) throws SerialException { isValid(); Object dst = new Object[count]; System.arraycopy((Object) elements, (int) index, dst, 0, count); return dst; } /** * Returns a new array that is a copy of a slice * of this <code>SerialArray</code> object, starting with the * element at the given index and containing the given number * of consecutive elements. * <P> * This method does custom mapping if the array elements are a UDT * and the given type map has an entry for that UDT. * Custom mapping is recursive, * meaning that if, for instance, an element of an SQL structured type * is an SQL structured type that itself has an element that is an SQL * structured type, each structured type that has a custom mapping will be * mapped according to the given type map. * * @param index the index into this <code>SerialArray</code> object * of the first element to be copied; the index of the * first element in the array is <code>0</code> * @param count the number of consecutive elements to be copied, starting * at the given index * @param map a <code>java.util.Map</code> object in which * each entry consists of 1) a <code>String</code> object * giving the fully qualified name of a UDT and 2) the * <code>Class</code> object for the <code>SQLData</code> implementation * that defines how the UDT is to be mapped * @return a copy of the designated elements in this <code>SerialArray</code> * object as an <code>Object</code> in the Java programming language * @throws SerialException if an error occurs; * if {@code free} had previously been called on this object */ public Object getArray(long index, int count, Map<String, Class<?>> map) throws SerialException { isValid(); Object dst = new Object[count]; System.arraycopy((Object) elements, (int) index, dst, 0, count); return dst; } /** * Retrieves the SQL type of the elements in this <code>SerialArray</code> * object. The <code>int</code> returned is one of the constants in the class * <code>java.sql.Types</code>. * * @return one of the constants in <code>java.sql.Types</code>, indicating * the SQL type of the elements in this <code>SerialArray</code> object * @throws SerialException if an error occurs; * if {@code free} had previously been called on this object */ public int getBaseType() throws SerialException { isValid(); return baseType; } /** * Retrieves the DBMS-specific type name for the elements in this * <code>SerialArray</code> object. * * @return the SQL type name used by the DBMS for the base type of this * <code>SerialArray</code> object * @throws SerialException if an error occurs; * if {@code free} had previously been called on this object */ public String getBaseTypeName() throws SerialException { isValid(); return baseTypeName; } /** * Retrieves a <code>ResultSet</code> object holding the elements of * the subarray that starts at * index <i>index</i> and contains up to <i>count</i> successive elements. * This method uses the connection's type map to map the elements of * the array if the map contains * an entry for the base type. Otherwise, the standard mapping is used. * * @param index the index into this <code>SerialArray</code> object * of the first element to be copied; the index of the * first element in the array is <code>0</code> * @param count the number of consecutive elements to be copied, starting * at the given index * @return a <code>ResultSet</code> object containing the designated * elements in this <code>SerialArray</code> object, with a * separate row for each element * @throws SerialException if called with the cause set to * {@code UnsupportedOperationException} */ public ResultSet getResultSet(long index, int count) throws SerialException { SerialException se = new SerialException(); se.initCause(new UnsupportedOperationException()); throw se; } /** * * Retrieves a <code>ResultSet</code> object that contains all of * the elements of the SQL <code>ARRAY</code> * value represented by this <code>SerialArray</code> object. This method uses * the specified map for type map customizations unless the base type of the * array does not match a user-defined type (UDT) in <i>map</i>, in * which case it uses the * standard mapping. This version of the method <code>getResultSet</code> * uses either the given type map or the standard mapping; it never uses the * type map associated with the connection. * * @param map a <code>java.util.Map</code> object in which * each entry consists of 1) a <code>String</code> object * giving the fully qualified name of a UDT and 2) the * <code>Class</code> object for the <code>SQLData</code> implementation * that defines how the UDT is to be mapped * @return a <code>ResultSet</code> object containing all of the * elements in this <code>SerialArray</code> object, with a * separate row for each element * @throws SerialException if called with the cause set to * {@code UnsupportedOperationException} */ public ResultSet getResultSet(Map<String, Class<?>> map) throws SerialException { SerialException se = new SerialException(); se.initCause(new UnsupportedOperationException()); throw se; } /** * Retrieves a <code>ResultSet</code> object that contains all of * the elements in the <code>ARRAY</code> value that this * <code>SerialArray</code> object represents. * If appropriate, the elements of the array are mapped using the connection's * type map; otherwise, the standard mapping is used. * * @return a <code>ResultSet</code> object containing all of the * elements in this <code>SerialArray</code> object, with a * separate row for each element * @throws SerialException if called with the cause set to * {@code UnsupportedOperationException} */ public ResultSet getResultSet() throws SerialException { SerialException se = new SerialException(); se.initCause(new UnsupportedOperationException()); throw se; } /** * Retrieves a result set holding the elements of the subarray that starts at * Retrieves a <code>ResultSet</code> object that contains a subarray of the * elements in this <code>SerialArray</code> object, starting at * index <i>index</i> and containing up to <i>count</i> successive * elements. This method uses * the specified map for type map customizations unless the base type of the * array does not match a user-defined type (UDT) in <i>map</i>, in * which case it uses the * standard mapping. This version of the method <code>getResultSet</code> uses * either the given type map or the standard mapping; it never uses the type * map associated with the connection. * * @param index the index into this <code>SerialArray</code> object * of the first element to be copied; the index of the * first element in the array is <code>0</code> * @param count the number of consecutive elements to be copied, starting * at the given index * @param map a <code>java.util.Map</code> object in which * each entry consists of 1) a <code>String</code> object * giving the fully qualified name of a UDT and 2) the * <code>Class</code> object for the <code>SQLData</code> implementation * that defines how the UDT is to be mapped * @return a <code>ResultSet</code> object containing the designated * elements in this <code>SerialArray</code> object, with a * separate row for each element * @throws SerialException if called with the cause set to * {@code UnsupportedOperationException} */ public ResultSet getResultSet(long index, int count, Map<String, Class<?>> map) throws SerialException { SerialException se = new SerialException(); se.initCause(new UnsupportedOperationException()); throw se; } /** * Compares this SerialArray to the specified object. The result is {@code * true} if and only if the argument is not {@code null} and is a {@code * SerialArray} object whose elements are identical to this object's elements * * @param obj The object to compare this {@code SerialArray} against * * @return {@code true} if the given object represents a {@code SerialArray} * equivalent to this SerialArray, {@code false} otherwise * */ public boolean equals(Object obj) { if (this == obj) { return true; } if (obj instanceof SerialArray) { SerialArray sa = (SerialArray) obj; return baseType == sa.baseType && baseTypeName.equals(sa.baseTypeName) && Arrays.equals(elements, sa.elements); } return false; } /** * Returns a hash code for this SerialArray. The hash code for a * {@code SerialArray} object is computed using the hash codes * of the elements of the {@code SerialArray} object * * @return a hash code value for this object. */ public int hashCode() { return (((31 + Arrays.hashCode(elements)) * 31 + len) * 31 + baseType) * 31 + baseTypeName.hashCode(); } /** * Returns a clone of this {@code SerialArray}. The copy will contain a * reference to a clone of the underlying objects array, not a reference * to the original underlying object array of this {@code SerialArray} object. * * @return a clone of this SerialArray */ public Object clone() { try { SerialArray sa = (SerialArray) super.clone(); sa.elements = (elements != null) ? Arrays.copyOf(elements, len) : null; return sa; } catch (CloneNotSupportedException ex) { // this shouldn't happen, since we are Cloneable throw new InternalError(); } } /** * readObject is called to restore the state of the {@code SerialArray} from * a stream. */ private void readObject(ObjectInputStream s) throws IOException, ClassNotFoundException { ObjectInputStream.GetField fields = s.readFields(); Object[] tmp = (Object[]) fields.get("elements", null); if (tmp == null) throw new InvalidObjectException("elements is null and should not be!"); elements = tmp.clone(); len = fields.get("len", 0); if (elements.length != len) throw new InvalidObjectException("elements is not the expected size"); baseType = fields.get("baseType", 0); baseTypeName = (String) fields.get("baseTypeName", null); } /** * writeObject is called to save the state of the {@code SerialArray} * to a stream. */ private void writeObject(ObjectOutputStream s) throws IOException { ObjectOutputStream.PutField fields = s.putFields(); fields.put("elements", elements); fields.put("len", len); fields.put("baseType", baseType); fields.put("baseTypeName", baseTypeName); s.writeFields(); } /** * Check to see if this object had previously had its {@code free} method * called * * @throws SerialException */ private void isValid() throws SerialException { if (elements == null) { throw new SerialException( "Error: You cannot call a method on a " + "SerialArray instance once free() has been called."); } } /** * The identifier that assists in the serialization of this <code>SerialArray</code> * object. */ static final long serialVersionUID = -8466174297270688520L; }