JdbcRowMapper-JDBC泛型查询对象封装

JdbcRowMapper-JDBC泛型查询对象封装

@Table(name = "user")
@Column(name="last_name")

package com.sun4j.data.jdbc.util;

import java.beans.PropertyDescriptor;
import java.lang.reflect.Field;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Locale;
import java.util.Map;
import java.util.Set;
import javax.persistence.Column;
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.ClassUtils;
import org.springframework.util.StringUtils;

public class JdbcRowMapper<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 {@code BeanPropertyRowMapper} for bean-style configuration.
* @see #setMappedClass
* @see #setCheckFullyPopulated
*/
public JdbcRowMapper() {
}

/**
* Create a new {@code 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 JdbcRowMapper(Class<T> mappedClass) {
initialize(mappedClass);
}

/**
* Create a new {@code 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 JdbcRowMapper(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 != mappedClass) {
throw new InvalidDataAccessApiUsageException("The mapped class can not be reassigned to map to " +
mappedClass + " since it is already providing mapping for " + this.mappedClass);
}
}
}

/**
* 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 this.primitivesDefaultedForNullValue;
}

/**
* 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) {
String name=pd.getName();
try {
Field field =mappedClass.getDeclaredField(pd.getName());
if (field!=null) {
Column column=field.getAnnotation(Column.class);
if (column!=null) {
name=column.name();
}
}
} catch (NoSuchFieldException e) {
e.printStackTrace();
} catch (SecurityException e) {
e.printStackTrace();
}
this.mappedFields.put(lowerCaseName(name), pd);
String underscoredName = underscoreName(name);
if (!lowerCaseName(name).equals(underscoredName)) {
this.mappedFields.put(underscoredName, pd);
}
this.mappedProperties.add(name);
}
}
}

/**
* 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 original name
* @return the converted name
* @since 4.2
* @see #lowerCaseName
*/
protected String underscoreName(String name) {
if (!StringUtils.hasLength(name)) {
return "";
}
StringBuilder result = new StringBuilder();
result.append(lowerCaseName(name.substring(0, 1)));
for (int i = 1; i < name.length(); i++) {
String s = name.substring(i, i + 1);
String slc = lowerCaseName(s);
if (!s.equals(slc)) {
result.append("_").append(slc);
}
else {
result.append(s);
}
}
return result.toString();
}

/**
* Convert the given name to lower case.
* By default, conversions will happen within the US locale.
* @param name the original name
* @return the converted name
* @since 4.2
*/
protected String lowerCaseName(String name) {
return name.toLowerCase(Locale.US);
}

/**
* 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);
String field = lowerCaseName(column.replaceAll(" ", ""));
PropertyDescriptor pd = this.mappedFields.get(field);
if (pd != null) {
try {
Object value = getColumnValue(rs, index, pd);
if (rowNumber == 0 && logger.isDebugEnabled()) {
logger.debug("Mapping column '" + column + "' to property '" + pd.getName() +
"' of type [" + ClassUtils.getQualifiedName(pd.getPropertyType()) + "]");
}
try {
bw.setPropertyValue(pd.getName(), value);
}
catch (TypeMismatchException ex) {
if (value == null && this.primitivesDefaultedForNullValue) {
if (logger.isDebugEnabled()) {
logger.debug("Intercepted TypeMismatchException for row " + rowNumber +
" and column '" + column + "' with null value when setting property '" +
pd.getName() + "' of type [" +
ClassUtils.getQualifiedName(pd.getPropertyType()) +
"] on object: " + mappedObject, ex);
}
}
else {
throw ex;
}
}
if (populatedProperties != null) {
populatedProperties.add(pd.getName());
}
}
catch (NotWritablePropertyException ex) {
throw new DataRetrievalFailureException(
"Unable to map column '" + column + "' to property '" + pd.getName() + "'", ex);
}
}
else {
// No PropertyDescriptor found
if (rowNumber == 0 && logger.isDebugEnabled()) {
logger.debug("No property found for column '" + column + "' mapped to field '" + field + "'");
}
}
}

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.getName() + "]: " +
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 {@code BeanPropertyRowMapper}
* (with the mapped class specified only once).
* @param mappedClass the class that each row should be mapped to
*/
public static <T> JdbcRowMapper<T> newInstance(Class<T> mappedClass) {
return new JdbcRowMapper<T>(mappedClass);
}
}

使用示例：

@Override
public T load(Serializable id) {
String sql = "SELECT * FROM " + getTableName() + " WHERE id=?";
return jdbcTemplate.query(sql, JdbcRowMapper.newInstance(entityClass()), id).get(0);
}

@Override
public List<T> findAll(String sql, Object... args) {
return jdbcTemplate.query(sql, JdbcRowMapper.newInstance(entityClass()), args);
}

获取泛型类：

private Class<T> entityClass() {
return entityInformation.getJavaType(); //此处可以使用正常的获取泛型类的方式
}

**或者**

private Class<T> entityClass;
@SuppressWarnings("unchecked")
public JdbcBaseDaoImpl() {
ParameterizedType type = (ParameterizedType) getClass().getGenericSuperclass();
entityClass = (Class<T>) type.getActualTypeArguments()[0];
System.out.println("Dao实现类是：" + entityClass.getName());
}

获取表名：

private String getTableName() {
String name = entityClass().getAnnotation(Table.class).name();
if (StringUtils.isNotBlank(name)) {
return name;
} else {
return entityClass().getSimpleName();
}
}