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An extremely lightweight data access layer over JDBC
package com.dieselpoint.norm;
import java.beans.BeanInfo;
import java.beans.IntrospectionException;
import java.beans.Introspector;
import java.beans.PropertyDescriptor;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.util.ArrayList;
import java.util.Collection;
import java.util.LinkedHashMap;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.Table;
import javax.persistence.Transient;
/**
* Provides means of reading and writing properties in a pojo.
*/
public class PojoInfo {
/*
* annotations recognized: @ Id, @ GeneratedValue @ transient @ table
*/
private LinkedHashMap propertyMap = new LinkedHashMap();
private String table;
private String primaryKeyName;
private String generatedColumnName;
//private String [] columns;
//private String commaColumns;
private String insertSql;
private int insertSqlArgCount;
private String [] insertColumnNames;
private String selectColumns;
private String updateSql;
private String[] updateColumnNames;
private int updateSqlArgCount;
static class Property {
String name;
Method readMethod;
Method writeMethod;
Field field;
Class dataType;
boolean isGenerated;
boolean isPrimaryKey;
boolean isEnumField;
Class enumClass;
}
public PojoInfo(Class clazz) throws IntrospectionException {
for (Field field: clazz.getFields()) {
if (Modifier.isPublic(field.getModifiers())) {
if (field.getAnnotation(Transient.class) != null) {
continue;
}
Property pair = new Property();
pair.name = field.getName();
pair.field = field;
pair.dataType = field.getType();
if (field.getAnnotation(Id.class) != null) {
pair.isPrimaryKey = true;
primaryKeyName = field.getName();
}
if (field.getAnnotation(GeneratedValue.class) != null) {
generatedColumnName = field.getName();
pair.isGenerated = true;
}
if (field.getType().isEnum()) {
pair.isEnumField = true;
pair.enumClass = (Class) field.getType();
}
propertyMap.put(pair.name, pair);
}
}
BeanInfo beanInfo = Introspector.getBeanInfo(clazz, Object.class);
PropertyDescriptor[] descriptors = beanInfo.getPropertyDescriptors();
for (PropertyDescriptor descriptor : descriptors) {
String name = descriptor.getName();
Property pair = new Property();
pair.name = name;
pair.readMethod = getMethod(descriptor.getReadMethod(), name, pair);
pair.writeMethod = getMethod(descriptor.getWriteMethod(), name, pair);
pair.dataType = descriptor.getPropertyType();
propertyMap.put(name, pair);
}
Table annot = (Table) clazz.getAnnotation(Table.class);
if (annot != null) {
table = annot.name();
} else {
table = clazz.getSimpleName();
}
makeInsertSql();
makeUpdateSql();
makeSelectColumns();
}
/*
private void makeColumns() {
columns = new String [map.size()];
map.keySet().toArray(columns);
StringBuilder buf = new StringBuilder();
for (int i = 0; i < columns.length; i++) {
if (buf.length() > 0) {
buf.append(',');
}
buf.append(columns[i]);
}
commaColumns = buf.toString();
}
*/
private Method getMethod(Method meth, String propertyName, Property pair) {
if (meth == null) {
return null;
}
if (meth.getAnnotation(Transient.class) != null) {
return null;
}
if (meth.getAnnotation(Id.class) != null) {
this.primaryKeyName = propertyName;
pair.isPrimaryKey = true;
}
if (meth.getAnnotation(GeneratedValue.class) != null) {
this.generatedColumnName = propertyName;
pair.isGenerated = true;
}
return meth;
}
public Object getValue(Object pojo, String name) throws NoSuchFieldException, IllegalAccessException, IllegalArgumentException, InvocationTargetException {
Property prop = propertyMap.get(name);
if (prop == null) {
throw new NoSuchFieldException(name);
}
if (prop.readMethod != null) {
return prop.readMethod.invoke(pojo);
}
if (prop.isEnumField) {
// convert all enums to string
Object o = prop.field.get(pojo);
if (o == null) {
return null;
} else {
return o.toString();
}
}
if (prop.field != null) {
return prop.field.get(pojo);
}
return null;
}
public void putValue(Object pojo, String name, Object value) throws NoSuchFieldException, IllegalAccessException, IllegalArgumentException, InvocationTargetException {
Property pair = propertyMap.get(name);
if (pair == null) {
throw new NoSuchFieldException(name);
}
if (pair.writeMethod != null) {
pair.writeMethod.invoke(pojo, value);
return;
}
if (pair.field != null) {
Object val = value;
if (pair.isEnumField) {
// convert to enum const
val = getEnumConst(pair.enumClass, value.toString());
}
pair.field.set(pojo, val);
return;
}
}
private > Object getEnumConst(Class enumType, String o) {
return Enum.valueOf(enumType, o);
}
public String getTable() {
return table;
}
public Collection getProperties() {
return propertyMap.values();
}
public Property getProperty(String columnName) {
return propertyMap.get(columnName);
}
public String getPrimaryKeyName() {
return primaryKeyName;
}
//public String[] getColumns() {
// return columns;
//}
//public String getCommaColumns() {
// return commaColumns;
//}
public String getGeneratedColumnName() {
return generatedColumnName;
}
private void makeInsertSql() {
ArrayList cols = new ArrayList();
for (Property prop: propertyMap.values()) {
if (prop.isGenerated) {
continue;
}
cols.add(prop.name);
}
insertColumnNames = cols.toArray(new String [cols.size()]);
insertSqlArgCount = insertColumnNames.length;
StringBuilder buf = new StringBuilder();
buf.append("insert into ");
buf.append(getTable());
buf.append(" (");
buf.append(Util.join(insertColumnNames)); // comma sep list?
buf.append(") values (");
buf.append(Util.getQuestionMarks(insertSqlArgCount));
buf.append(")");
insertSql = buf.toString();
}
private void makeUpdateSql() {
ArrayList cols = new ArrayList();
for (Property prop: propertyMap.values()) {
if (prop.isPrimaryKey) {
continue;
}
if (prop.isGenerated) {
continue;
}
cols.add(prop.name);
}
updateColumnNames = cols.toArray(new String [cols.size()]);
updateSqlArgCount = updateColumnNames.length + 1; // + 1 for the where arg
StringBuilder buf = new StringBuilder();
buf.append("update ");
buf.append(getTable());
buf.append(" set ");
for (int i = 0; i < cols.size(); i++) {
if (i > 0) {
buf.append(',');
}
buf.append(cols.get(i) + "=?");
}
buf.append(" where " + primaryKeyName + "=?");
updateSql = buf.toString();
}
public Object[] getInsertArgs(Object row) throws NoSuchFieldException, IllegalAccessException, IllegalArgumentException, InvocationTargetException {
Object [] args = new Object[insertSqlArgCount];
for (int i = 0; i < insertSqlArgCount; i++) {
args[i] = getValue(row, insertColumnNames[i]);
}
return args;
}
public Object[] getUpdateArgs(Object row) throws NoSuchFieldException, IllegalAccessException, IllegalArgumentException, InvocationTargetException {
Object [] args = new Object[updateSqlArgCount];
for (int i = 0; i < updateSqlArgCount - 1; i++) {
args[i] = getValue(row, updateColumnNames[i]);
}
// add the value for the where clause to the end
Object pk = getValue(row, primaryKeyName);
args[updateSqlArgCount - 1] = pk;
return args;
}
public String getInsertSql() {
return insertSql;
}
private void makeSelectColumns() {
ArrayList cols = new ArrayList();
for (Property prop: propertyMap.values()) {
cols.add(prop.name);
}
selectColumns = Util.join(cols);
}
public String getSelectColumns() {
return selectColumns;
}
public String getUpdateSql() {
return updateSql;
}
}