jdbcTemplate.queryForList的返回类型（sql，object，classType）

我正在使用jdbcTemplate.queryForList以下列方式执行命名查询：

List conversations = jdbcTemplate.queryForList( SELECT_ALL_CONVERSATIONS_SQL_FULL, new Object[] {userId, dateFrom, dateTo}); 

SQL查询是：

 private final String SELECT_ALL_CONVERSATIONS_SQL_FULL = "select conversation.conversationID, conversation.room, " + "conversation.isExternal, conversation.startDate, " + "conversation.lastActivity, conversation.messageCount " + "from openfire.ofconversation conversation " + "WHERE conversation.conversationid IN " + "(SELECT conversation.conversationID " + "FROM openfire.ofconversation conversation, " + "openfire.ofconparticipant participant " + "WHERE conversation.conversationID = participant.conversationID " + "AND participant.bareJID LIKE ? " + "AND conversation.startDate between ? AND ?)"; 

但是，当以下列方式提取列表的内容时：

 for (Conversation conversation : conversations) { builder.append(conversation.getId()); builder.append(","); builder.append(conversation.getRoom()); builder.append(","); builder.append(conversation.getIsExternal()); builder.append(","); builder.append(conversation.getStartDate()); builder.append(","); builder.append(conversation.getEndDate()); builder.append(","); builder.append(conversation.getMsgCount()); out.write(builder.toString()); } 

我收到一个错误：

 java.util.LinkedHashMap cannot be cast to net.org.messagehistory.model.Conversation 

如何将此linkedMap转换为所需的Object？

谢谢

Answer 1

为了将查询的结果集映射到特定的Java类，您可能最好（假设您有兴趣在其他地方使用该对象）与RowMapper一起将结果集中的列转换为对象实例。

有关如何使用行映射器的信息，请参见使用JDBC访问数据的第12.2.1.1节 。

简而言之，你需要这样的东西：

 List actors = jdbcTemplate.query( SELECT_ALL_CONVERSATIONS_SQL_FULL, new Object[] {userId, dateFrom, dateTo}, new RowMapper() { public Conversation mapRow(ResultSet rs, int rowNum) throws SQLException { Conversation c = new Conversation(); c.setId(rs.getLong(1)); c.setRoom(rs.getString(2)); [...] return c; } }); 

Answer 2

JdbcTemplate，NamedParameterJdbcTemplate的完整解决方案，带或不带RowMapper示例。

//创建一个Employee表

 create table employee( id number(10), name varchar2(100), salary number(10) ); 

================================================== ===================== //Employee.java

 public class Employee { private int id; private String name; private float salary; //no-arg and parameterized constructors public Employee(){}; public Employee(int id, String name, float salary){ this.id=id; this.name=name; this.salary=salary; } //getters and setters public int getId() { return id; } public void setId(int id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public float getSalary() { return salary; } public void setSalary(float salary) { this.salary = salary; } public String toString(){ return id+" "+name+" "+salary; } } 

================================================== ======================= //EmployeeDao.java

 import java.sql.ResultSet; import java.sql.SQLException; import java.util.HashMap; import java.util.Iterator; import java.util.List; import java.util.Map; import org.springframework.jdbc.core.JdbcTemplate; import org.springframework.jdbc.core.RowMapper; import org.springframework.jdbc.core.namedparam.NamedParameterJdbcTemplate; public class EmployeeDao { private JdbcTemplate jdbcTemplate; private NamedParameterJdbcTemplate nameTemplate; public void setnameTemplate(NamedParameterJdbcTemplate template) { this.nameTemplate = template; } public void setJdbcTemplate(JdbcTemplate jdbcTemplate) { this.jdbcTemplate = jdbcTemplate; } // BY using JdbcTemplate public int saveEmployee(Employee e){ int id = e.getId(); String name = e.getName(); float salary = e.getSalary(); Object p[] = {id, name, salary}; String query="insert into employee values(?,?,?)"; return jdbcTemplate.update(query, p); /*String query="insert into employee values('"+e.getId()+"','"+e.getName()+"','"+e.getSalary()+"')"; return jdbcTemplate.update(query); */ } //By using NameParameterTemplate public void insertEmploye(Employee e) { String query="insert into employee values (:id,:name,:salary)"; Map map=new HashMap(); map.put("id",e.getId()); map.put("name",e.getName()); map.put("salary",e.getSalary()); nameTemplate.execute(query,map,new MyPreparedStatement()); } // Updating Employee public int updateEmployee(Employee e){ String query="update employee set name='"+e.getName()+"',salary='"+e.getSalary()+"' where id='"+e.getId()+"' "; return jdbcTemplate.update(query); } // Deleting a Employee row public int deleteEmployee(Employee e){ String query="delete from employee where id='"+e.getId()+"' "; return jdbcTemplate.update(query); } //Selecting Single row with condition and also all rows public int selectEmployee(Employee e){ //String query="select * from employee where id='"+e.getId()+"' "; String query="select * from employee"; List> rows = jdbcTemplate.queryForList(query); for(Map row : rows){ String id = row.get("id").toString(); String name = (String)row.get("name"); String salary = row.get("salary").toString(); System.out.println(id + " " + name + " " + salary ); } return 1; } // Can use MyrowMapper class an implementation class for RowMapper interface public void getAllEmployee() { String query="select * from employee"; List l = jdbcTemplate.query(query, new MyrowMapper()); Iterator it=l.iterator(); while(it.hasNext()) { Employee e=(Employee)it.next(); System.out.println(e.getId()+" "+e.getName()+" "+e.getSalary()); } } //Can use directly a RowMapper implementation class without an object creation public List getAllEmployee1(){ return jdbcTemplate.query("select * from employee",new RowMapper(){ @Override public Employee mapRow(ResultSet rs, int rownumber) throws SQLException { Employee e=new Employee(); e.setId(rs.getInt(1)); e.setName(rs.getString(2)); e.setSalary(rs.getFloat(3)); return e; } }); } // End of all the function } 

================================================== ============== //MyrowMapper.java

  import java.sql.ResultSet; import java.sql.SQLException; import org.springframework.jdbc.core.RowMapper; public class MyrowMapper implements RowMapper { @Override public Employee mapRow(ResultSet rs, int rownumber) throws SQLException { System.out.println("mapRow()====:"+rownumber); Employee e=new Employee(); e.setId(rs.getInt("id")); e.setName(rs.getString("name")); e.setSalary(rs.getFloat("salary")); return e; } } 

================================================== ======== // MyPreparedStatement.java

 import java.sql.PreparedStatement; import java.sql.SQLException; import org.springframework.dao.DataAccessException; import org.springframework.jdbc.core.PreparedStatementCallback; public class MyPreparedStatement implements PreparedStatementCallback 

================================================== =================== //Test.java

 import java.util.List; import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext; public class Test { public static void main(String[] args) { ApplicationContext ctx=new ClassPathXmlApplicationContext("applicationContext.xml"); EmployeeDao dao=(EmployeeDao)ctx.getBean("edao"); // By calling constructor for insert /* int status=dao.saveEmployee(new Employee(103,"Ajay",35000)); System.out.println(status); */ // By calling PreparedStatement dao.insertEmploye(new Employee(103,"Roh",25000)); // By calling setter-getter for update /* Employee e=new Employee(); e.setId(102); e.setName("Rohit"); e.setSalary(8000000); int status=dao.updateEmployee(e); */ // By calling constructor for update /* int status=dao.updateEmployee(new Employee(102,"Sadhan",15000)); System.out.println(status); */ // Deleting a record /* Employee e=new Employee(); e.setId(102); int status=dao.deleteEmployee(e); System.out.println(status); */ // Selecting single or all rows /* Employee e=new Employee(); e.setId(102); int status=dao.selectEmployee(e); System.out.println(status); */ // Can use MyrowMapper class an implementation class for RowMapper interface dao.getAllEmployee(); // Can use directly a RowMapper implementation class without an object creation /* List list=dao.getAllEmployee1(); for(Employee e1:list) System.out.println(e1); */ } } 

================================================== ================ //applicationContext.xml

================================================== =================

Answer 3

 List> List = getJdbcTemplate().queryForList(SELECT_ALL_CONVERSATIONS_SQL_FULL, new Object[] {userId, dateFrom, dateTo}); for (Map rowMap : resultList) { DTO dTO = new DTO(); dTO.setrarchyID((Long) (rowMap.get("ID"))); } 

Answer 4

queryForList返回LinkedHashMap对象的List。

你需要像这样首先抛出它：

     List list = jdbcTemplate.queryForList（...）;
     for（Object o：list）{
       地图m =（地图）o;
        ...
     }