spring data jpa 想使用EntityManager 对sql 进行处理四种方式（第四种本人改写的）

た入场券 2022-06-18 05:29 128阅读 0赞

下面看看主体的一个类：

package com.chinait.service.impl;
    
    import java.util.List;
    
    import javax.persistence.EntityManager;
    import javax.persistence.PersistenceContext;
    import javax.websocket.server.ServerEndpoint;
    
    import org.hibernate.SQLQuery;
    import org.hibernate.Session;
    import org.hibernate.transform.Transformers;
    import org.springframework.stereotype.Service;
    
    import com.chinait.service.TestService;
    import com.chinait.utils.Testtrans;
    import com.chinait.vo.Test;
    
    @Service
    public class TestServiceImpl implements TestService{
    	@PersistenceContext
    	private EntityManager entityManager;
    	@Override	
    	public void getTest(){
    		String sql = "select apps.appName,source.cutPath,sourcetype.sourceTypeName from apps join source on source.apps_id = apps.id join sourcetype on sourcetype.id = source.sourceType_id";
    		Session session = entityManager.unwrap(org.hibernate.Session.class);
    		//返回类型是List<map>
    		SQLQuery query2 = session.createSQLQuery(sql);
    		query2.setResultTransformer(Transformers.ALIAS_TO_ENTITY_MAP);
    		System.out.println("查询数据返回map"+query2.list());
    		//返回数据是list<List<Object>>
    		SQLQuery query3 = session.createSQLQuery(sql);
    		query2.setResultTransformer(Transformers.TO_LIST);
    		System.out.println("查询数据返回map"+query2.list());
    		//返回类型是可定制化对象
    		SQLQuery query = session.createSQLQuery(sql);
    		Testtrans Testtrans = new Testtrans(Test.class);
    		query.setResultTransformer(Testtrans);
    		List<Test> list = (List<Test>)query.list();
    		System.out.println("查询数据返回对象"+list);
    		//返回数据是对象,首先这个方法有点坑，因为它需要去找寻bean 对应的对象是否是放在spring data jpa 的entity 如果不是的话回报错
    		/*SQLQuery query4 = session.createSQLQuery(sql);
    		query.setResultTransformer(Transformers.aliasToBean(Test.class));
    		List<Test> list3 = (List<Test>)query.list();
    		System.out.println("查询数据返回对象"+list);*/
    	}
    }

下面则是：我重写的一个类的源码：

package com.chinait.utils;
    
    import java.lang.reflect.Method;
    import java.lang.reflect.Modifier;
    import java.util.ArrayList;
    import java.util.List;
    
    import org.hibernate.transform.AliasToBeanResultTransformer;
    
    
    public class Testtrans extends AliasToBeanResultTransformer{
    	private Class resultClass;
    	public Testtrans(Class resultClass) {
    		super(resultClass);
    		this.resultClass = resultClass;
    	}
    
    	private static final long serialVersionUID = 1L;
    
    	public List transformTuple(Object[] tuple, String[] aliases) {
    		  List list = new ArrayList();
    		  Object obj = null;
    			try {
    				obj = resultClass.newInstance();
    			} catch (InstantiationException e1) {
    				e1.printStackTrace();
    			} catch (IllegalAccessException e1) {
    				e1.printStackTrace();
    			}
    		  Method[] methods = resultClass.getMethods();// 返回这个类里面方法的集合  
    		  for(int k=0;k<aliases.length;k++){
    			  String aliase=aliases[k];
    			  char[] ch = aliase.toCharArray();  
    			  ch[0] = Character.toUpperCase(ch[0]);  
    			  String s = new String(ch);  
    			  String[] names = new String[] { ("set" + s).intern(),  
    			    ("get" + s).intern(), ("is" + s).intern(),  
    			    ("read" + s).intern() };  
    			  Method setter = null;  
    			  Method getter = null;  
    			  int length = methods.length;  
    			  for (int i = 0; i < length; ++i) {  
    			   Method method = methods[i];  
    			   /** 
    			    * 检查该方法是否为公共方法,如果非公共方法就继续 
    			    */  
    			   if (!Modifier.isPublic(method.getModifiers()))  
    			    continue;  
    			   String methodName = method.getName();  
    			  
    			   for (String name : names) {  
    			    if (name.equals(methodName)) {  
    			     if (name.startsWith("set") || name.startsWith("read"))  
    			      setter = method;  
    			     else if (name.startsWith("get") || name.startsWith("is"))  
    			      getter = method;  
    			  
    			    }  
    			   }  
    			  }
    			  if(getter!=null){
    				  Object[] param = buildParam(getter.getReturnType().getName(), tuple[k]);  
    				  try {  
    				   setter.invoke(obj, param);
    				  } catch (Exception e) {  
    				   e.printStackTrace();  
    				  }
    			  }
    		  }
    		  list.add(obj);
    		  return list;
    	}
    	private final static Object[] buildParam(String paramType, Object value) {  
    		  Object[] param = new Object[1];  
    		  if (paramType.equalsIgnoreCase("java.lang.String")) {  
    		   param[0] = (String)(value);  
    		  } else if (paramType.equalsIgnoreCase("int")  
    		    || paramType.equalsIgnoreCase("java.lang.Integer")) {  
    		   param[0] = (Integer)(value);  
    		  } else if (paramType.equalsIgnoreCase("long")|| paramType.equalsIgnoreCase("java.lang.Long")) {  
    		   param[0] = (Long)(value);  
    		  } else if (paramType.equalsIgnoreCase("double")|| paramType.equalsIgnoreCase("java.lang.Double")) {  
    		   param[0] = (Double)(value);  
    		  } else if (paramType.equalsIgnoreCase("float")|| paramType.equalsIgnoreCase("java.lang.Float")) {  
    		   param[0] = (Float)(value);  
    		  } else if (paramType.equalsIgnoreCase("char")  
    		    || paramType.equalsIgnoreCase("Character")) {  
    		   param[0] = (char)(value);  
    		  }  
    		  return param;  
    	}  
    }

注意Test 的实体类：

package com.chinait.vo;
    //apps.appName,source.cutPath,sourcetype.sourceTypeName
    public class Test {
    	private String appName;
    	private String cutPath;
    	private String sourceTypeName;
    	public String getAppName() {
    		return appName;
    	}
    	public void setAppName(String appName) {
    		this.appName = appName;
    	}
    	public String getCutPath() {
    		return cutPath;
    	}
    	public void setCutPath(String cutPath) {
    		this.cutPath = cutPath;
    	}
    	public String getSourceTypeName() {
    		return sourceTypeName;
    	}
    	public void setSourceTypeName(String sourceTypeName) {
    		this.sourceTypeName = sourceTypeName;
    	}
    	@Override
    	public String toString() {
    		return "Test [appName=" + appName + ", cutPath=" + cutPath + ", sourceTypeName=" + sourceTypeName + "]";
    	}
    }

输出结果：

![Center][]

\*注意这里还有一个bug，那就是select \* 这里会报错，因为sqlquery 是按照字段的别名来判断数据与实体的对应关系。所以这里如果写成是select \* 回报一个异常是指无法匹配  
  
这边有兴趣的就是看这个源码。spring data jpa 想使用entityManager 对sql 进行处理四种方式（第四种本人改写的）。

[Center]: /images/20220618/b575adcc95604dae84a2cea62dd9129e.png