JPA 查询通过别名转实体

首先说缺点：映射的对象如果引用另外一个实体，是没办法映射。

使用的规则：别名和实体的属性要一一对应。

public class test｛
     private String name;

      private String password;

      //必须有get set方法，我这里就不写了
｝

sql 这样写: select aaa as name,bbb as password from tableName;

使用的：

Page<ApppintmentDepositFlowingReportVO> tList =

	(Page<ApppintmentDepositFlowingReportVO>) this.query(sql, ApppintmentDepositFlowingReportVO.class, pageable, "A");

最后一个参数 是 为 求 count 用的。后面我会 标出来。

public Page<?> query(String sql, Class<?> classs, Pageable pageable, String header) {

		EntityManager em = entityManagerFactory.createEntityManager();
		Session session = (Session) em.getDelegate();
		Sort sort = pageable.getSort();
		StringBuilder orderString = new StringBuilder();

		if (sort != null) {
			Iterator<Order> it = sort.iterator();
			if (it != null && it.hasNext()) {
				Order order = it.next();
				String dir = order.getDirection().toString();
				String name = order.getProperty();
				orderString.append(" order by ").append(name).append(" ").append(dir);
			}
		}

		SQLQuery query = session.createSQLQuery(sql + orderString.toString());

		String countSql = this.getSqlForCount(sql, header);
		SQLQuery query2 = session.createSQLQuery(countSql);
		Object obj = query2.uniqueResult();
		Long totleDatas = SqlResultUtil.getSqlResultLong(obj);
		query.setResultTransformer(new XaAliasToBeanResultTransformer(classs));
		query.setFirstResult((pageable.getPageNumber()) * pageable.getPageSize());
		query.setMaxResults(pageable.getPageSize());
		List<?> list = query.list();
		PageImpl<?> page = new PageImpl<>(list, pageable, totleDatas.longValue());
		em.close();
		return page;
	}

private String getSqlForCount(String sql, String header) {
		int d = sql.indexOf("from");
		return "select count(" + header + ".id) " + sql.substring(d);
	}

其实关键是这个类：

package com.baihui.base.util;

import java.util.Arrays;

import org.apache.commons.lang.StringUtils;
import org.hibernate.HibernateException;
import org.hibernate.property.ChainedPropertyAccessor;
import org.hibernate.property.PropertyAccessor;
import org.hibernate.property.PropertyAccessorFactory;
import org.hibernate.property.Setter;
import org.hibernate.transform.AliasToBeanResultTransformer;

public class XaAliasToBeanResultTransformer extends AliasToBeanResultTransformer {
	
	public Xa3itAliasToBeanResultTransformer(Class resultClasss) {
		super(resultClasss);
		this.resultClass = resultClasss;
	}

	private final Class resultClass;
	private boolean isInitialized;
	private String[] aliases;
	private Setter[] setters;


	@Override
	public boolean isTransformedValueATupleElement(String[] aliases, int tupleLength) {
		return false;
	}

	@Override
	public Object transformTuple(Object[] tuple, String[] aliases) {
		Object result;
		try {
			if ( ! isInitialized ) {
				initialize( aliases );
			}
			else {
				//check( aliases );
			}
			
			result = resultClass.newInstance();

			for ( int i = 0; i < aliases.length; i++ ) {
				Setter setter = setters[i];
				if ( setter != null ) 
				{
					Class[] clas = setter.getMethod().getParameterTypes();
					Object obj = this.getNewValObject(clas[0], tuple[i]);
					setter.set( result, obj, null );
				}
			}
		}
		catch ( InstantiationException e ) {
			throw new HibernateException( "Could not instantiate resultclass: " + resultClass.getName() );
		}
		catch ( IllegalAccessException e ) {
			throw new HibernateException( "Could not instantiate resultclass: " + resultClass.getName() );
		}

		return result;
	}

	private Object getNewValObject(Class clas,Object val)
	{
		if(val == null)
		{
			return null;
		}
		String name = clas.getName();
		if(StringUtils.equals(name, "java.lang.Long"))
		{
			return SqlResultUtil.getSqlResultLong(val);
		}
		else if(StringUtils.equals(name,"java.lang.Double"))
		{
			return SqlResultUtil.getSqlResultDouble(val);
		}
		else if(StringUtils.equals(name,"java.lang.Integer"))
		{
			return SqlResultUtil.getSqlResultInteger(val);
		}
		else if(StringUtils.equals(name,"java.util.Date"))
		{
			return SqlResultUtil.getSqlResultDate(val);
		}
		else if(StringUtils.equals(name,"boolean"))
		{
			String v = SqlResultUtil.getSqlResultString(val);
			return Boolean.parseBoolean(v);
		}
		
		else if(StringUtils.equals(name, "java.lang.Boolean"))
		{
			String v = SqlResultUtil.getSqlResultString(val);
			if(v.toLowerCase().equals("true") || v.toLowerCase().equals("false"))
			{
				return Boolean.parseBoolean(v);
			}
			else
			{
				if(v.equals("1"))
				{
					return Boolean.TRUE;
				}
				else
				{
					return Boolean.FALSE;
				}
			}
		}
		else if(StringUtils.equals(name,"java.lang.String"))
		{
			return SqlResultUtil.getSqlResultString(val);
		}
		return null;
	}
	private void initialize(String[] aliases) {
		PropertyAccessor propertyAccessor = new ChainedPropertyAccessor(
				new PropertyAccessor[] {
						PropertyAccessorFactory.getPropertyAccessor( resultClass, null ),
						PropertyAccessorFactory.getPropertyAccessor( "field" )
				}
		);
		this.aliases = new String[ aliases.length ];
		setters = new Setter[ aliases.length ];
		for ( int i = 0; i < aliases.length; i++ ) {
			String alias = aliases[ i ];
			if ( alias != null ) {
//				this.aliases[ i ] = alias;
				this.aliases[i] = this.getSqlAliasToJavaAlias(alias);
				setters[ i ] = propertyAccessor.getSetter( resultClass, this.aliases[i] );
			}
		}
		isInitialized = true;
	}
	
	private String getSqlAliasToJavaAlias(String s)
	{
		if(s.indexOf("_") > 0)
		{
			String[] sss = s.split("_");
			StringBuilder sb = new StringBuilder(sss[0]);
			for(int i = 1 ; i < sss.length;i++)
			{
				String ss = sss[i];
				String head = ss.substring(0,1);
				sb.append(head.toUpperCase()).append(ss.substring(1));
			}
			return sb.toString();
		}
		else
		{
			return s;
		}
	}
	
	private void check(String[] aliases) {
		if ( ! Arrays.equals( aliases, this.aliases ) ) {
			throw new IllegalStateException(
					"aliases are different from what is cached; aliases=" + Arrays.asList( aliases ) +
							" cached=" + Arrays.asList( this.aliases ) );
		}
	}

	@Override
	public boolean equals(Object o) {
		if ( this == o ) {
			return true;
		}
		if ( o == null || getClass() != o.getClass() ) {
			return false;
		}

		Xa3itAliasToBeanResultTransformer that = ( Xa3itAliasToBeanResultTransformer ) o;

		if ( ! resultClass.equals( that.resultClass ) ) {
			return false;
		}
		if ( ! Arrays.equals( aliases, that.aliases ) ) {
			return false;
		}

		return true;
	}

	@Override
	public int hashCode() {
		int result = resultClass.hashCode();
		result = 31 * result + ( aliases != null ? Arrays.hashCode( aliases ) : 0 );
		return result;
	}
}

就是参数中有个 page 因为用的是 spring data：

@ResponseBody
@RequestMapping(value = "operationOrderr", method = RequestMethod.POST)
public XaResult<Page<OperationOrderCashierFlowingReportForAOuterVO>> operationOrderCashierFlowingReportForAOuter(
HttpServletRequest request,
@RequestParam(defaultValue = "0") Integer nextPage,
@RequestParam(defaultValue = "10") Integer pageSize,
@RequestParam(defaultValue = "[{property:'A.id',direction:'DESC'}]") String sortData,
@RequestParam(defaultValue = "{}") String jsonFilter)
throws BusinessException {
Pageable pageable = WebUitl.buildPageRequest(nextPage, pageSize,sortData);
Map<String, Object> filterParams = WebUitl.getParametersStartingWith(jsonFilter, "search_");
XaResult<Page<OperationOrderCashierFlowingReportForAOuterVO>> xa = new XaResult<>();
try
{
Page<OperationOrderCashierFlowingReportForAOuterVO> p = this.operationOrderCashierFlowingReportForAOuterService.getResult(pageable, filterParams);
xa.success(p);
}catch(Exception e)
{
xa.error("数据查询出错");
}
return xa;
}

JPA 查询通过别名 转实体

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JPA 查询通过别名转实体