org.xillium.data.CachedResultSet Maven / Gradle / Ivy
package org.xillium.data;
import java.sql.*;
import java.util.*;
import java.lang.reflect.Field;
import org.xillium.base.beans.Beans;
import org.xillium.base.beans.Strings;
import org.xillium.base.beans.JSONBuilder;
import org.xillium.data.persistence.*;
import org.xillium.data.presentation.*;
/**
* A cached result set that is detached from any database connectivity.
*/
public class CachedResultSet {
public static final Builder BUILDER = new Builder();
/**
* The name of columns in the result set.
*/
public final String[] columns;
/**
* The rows of the result set with fields matching the column definition.
*/
public final List rows;
/**
* A ResultSetWorker implementation that builds a CachedResultSet.
*/
public static class Builder implements ResultSetWorker {
public CachedResultSet process(ResultSet rs) throws SQLException {
return new CachedResultSet(rs);
}
}
// for JAXB, Jackson, and possibly other libraries that use reflection to instantiate objects
private CachedResultSet() {
columns = null;
rows = null;
}
/**
* Retrieves the rows from a freshly obtained JDBC result set into a CachedResultSet.
* Closes the JDBC result set after retrieval.
*/
public CachedResultSet(ResultSet rset) throws SQLException {
try {
ResultSetMetaData metaData = rset.getMetaData();
int width = metaData.getColumnCount();
this.columns = new String[width];
for (int i = 0; i < width; ++i) {
columns[i] = Strings.toLowerCamelCase(metaData.getColumnLabel(i+1), '_');
}
if (rset.next()) {
this.rows = new ArrayList();
do {
Object[] row = new Object[width];
for (int i = 0; i < width; ++i) {
row[i] = rset.getObject(i+1);
}
rows.add(row);
} while (rset.next());
} else {
this.rows = null;
}
} finally {
rset.close();
}
}
/**
* Retrieves the rows from a collection of Objects, where the objects' (of type T) instance fields are taken as result set columns.
*/
public CachedResultSet(Collection collection) throws Exception {
this(collection, false);
}
/**
* Retrieves the rows from a collection of Objects, where the objects' (of type T) instance fields are taken as result set columns.
* Also performs presentation transformations if any is defined on the fields.
*/
public CachedResultSet(Collection collection, boolean forPresentation) throws Exception {
FieldRetriever[] retrievers = null;
this.rows = new ArrayList();
for (T object: collection) {
if (retrievers == null) {
if (forPresentation) {
retrievers = FieldFormatter.getFieldRetriever(Beans.getKnownInstanceFields(object.getClass()));
} else {
retrievers = FieldRetriever.getFieldRetriever(Beans.getKnownInstanceFields(object.getClass()));
}
}
Object[] row = new Object[retrievers.length];
for (int i = 0; i < retrievers.length; ++i) {
row[i] = retrievers[i].get(object);
}
rows.add(row);
}
int width = retrievers != null ? retrievers.length : 0;
this.columns = new String[width];
for (int i = 0; i < width; ++i) {
columns[i] = retrievers[i].field.getName();
}
}
/**
* Retrieves the rows from a collection of Objects, where the objects' (of type T) bean properties are taken as result set columns.
*/
public CachedResultSet(Collection collection, String... columns) {
this.columns = columns;
this.rows = new ArrayList();
for (T object: collection) {
Object[] row = new Object[columns.length];
for (int i = 0; i < columns.length; ++i) {
try {
Object value = columns[i].equals("-") ? object : Beans.invoke(object, "get"+Strings.capitalize(columns[i]));
if (value != null) {
if (value.getClass().isArray()) {
row[i] = Strings.join(value, ';');
} else {
row[i] = value.toString();
}
} else {
row[i] = null;
}
} catch (Exception x) {
row[i] = null;
}
}
rows.add(row);
}
}
/**
* Retrieves the rows from a collection of Objects, where a subset of the objects' (of type T) public fields are taken as result set columns.
*
* @param the type of the objects in the collection
* @param collection a collection of objects
* @param columns names of a select subset of each object's public fields
* @return the result set from the list of objects
*/
public static CachedResultSet chooseFields(Collection collection, String... columns) {
CachedResultSet rs = new CachedResultSet(columns, new ArrayList());
for (T object: collection) {
Object[] row = new Object[columns.length];
for (int i = 0; i < columns.length; ++i) {
try {
Object value = Beans.getKnownField(object.getClass(), columns[i]).get(object);
if (value != null) {
if (value.getClass().isArray()) {
row[i] = Strings.join(value, ';');
} else {
row[i] = value.toString();
}
} else {
row[i] = null;
}
} catch (Exception x) {
row[i] = null;
}
}
rs.rows.add(row);
}
return rs;
}
/**
* Retrieves the contents of this result set as a List of DataObjects.
*
* @param the type of the objects to be in the list
* @param type the class of the objects to be in the list
* @return the list of objects
* @throws InstantiationException if new instances of the given class can't be created
* @throws IllegalAccessException if the fields of the given type can't be read or updated
*/
public List asList(Class type) throws InstantiationException, IllegalAccessException {
Map fields = new HashMap();
for (String column: columns) try { fields.put(column, Beans.getKnownField(type, column)); } catch (Exception x) {}
List list = new ArrayList();
for (Object[] row: rows) {
T object = type.newInstance();
for (int i = 0; i < row.length; ++i) {
Field field = fields.get(columns[i]);
if (field != null) {
Beans.setValue(object, field, row[i]);
}
}
list.add(object);
}
return list;
}
/**
* Explicitly creates a CachedResultSet.
*
* @param columns the column names
* @param rows the data rows
*/
public CachedResultSet(String[] columns, List rows) {
this.columns = columns;
this.rows = rows;
}
/**
* Renames the columns of a CachedResultSet.
*
* @param names the new names of the columns, starting from the first column. If not enought new names are provided,
* the rest columns keep their original name.
* @return this object
*/
public CachedResultSet rename(String... names) {
for (int i = 0; i < names.length; ++i) {
this.columns[i] = names[i];
}
return this;
}
/**
* Builds a name-to-column index for quick access to data by columm names.
*
* @return a {@ Map} that maps column names to column positions starting from 0
*/
public Map buildIndex() {
Map index = new HashMap();
for (int i = 0; i < columns.length; ++i) {
index.put(columns[i], i);
}
return index;
}
/**
* Inside an object: serialized the cached result set into JSON.
*
* @param js a JSONBuilder to contain generated JSON text
* @return the JSONBuilder
*/
public JSONBuilder toJSON(JSONBuilder jb) {
return jb.append('{').serialize("columns", columns).append(',').serialize("rows", rows).append('}');
}
}