java为每个请求提供一个DAO访问

3 周，3 日 Questions & Answers 182

对于到达RESTAPI的每个请求，我必须实现对数据库的一次数据访问（CRUD调用）。实现线程安全的最佳方法是什么。目前，对于RESTAPI，我收到了一个请求。我可以将它添加到队列中。然后返回。我可以创建一个消费者线程，从队列中进行轮询。但是，如果您能深入了解如何使用线程安全的使用者线程对请求进行数据库访问，我将不胜感激。我使用spring访问DAO。这是我的刀课

package dao;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;

import javax.sql.DataSource;

import org.apache.commons.dbcp2.BasicDataSource;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.jdbc.core.PreparedStatementSetter;
import org.springframework.jdbc.core.RowMapper;
import org.springframework.jdbc.core.namedparam.SqlParameterSource;
import org.springframework.jdbc.core.support.JdbcDaoSupport;
import org.springframework.stereotype.Service;

import java.sql.ResultSet;
import java.sql.SQLException;

import org.springframework.jdbc.core.RowMapper;
import org.springframework.jdbc.datasource.DriverManagerDataSource;

import com.mysql.jdbc.PreparedStatement;

public class UserDAOImpl extends JdbcDaoSupport implements UserDAO 
{


    @Autowired
    private DriverManagerDataSource datasource;

private void setDataSource(DriverManagerDataSource datasource)
    {
        this.datasource = datasource;
    }

    @Override
      public List<User> getUsers(String userid) {
        //String query;
        String database_name="tennis.";
        String sql = " select distinct ux.id as user_id , ux.first_name, ux.last_name , lvl.rating as rating , photo.filename as file_name"+
                 "  from mytable.user as ux, "+database_name+"profile as pf , "+database_name+"level as lvl, mytable.photo as photo "+
                 "  where "+
                 "  ux.id = pf.user_id  "+
                 "  and ux.id = photo.user_id"+
                 "  and pf.level_id = lvl.id"+
                 "  and ux.id in "+
                 "  (  select  distinct user_id from "+database_name+"profile "+ 
                 "    where "+database_name+"profile.level_id in "+ 
                 "    (select l.id as levelid  "+
                 "  from "+database_name+"level as l "+
                 "  where l.rating  between "+
                 "  ( ( select distinct level.rating "+
                 "      from  "+database_name+"level, "+database_name+"profile "+
                 "      where level.id = profile.level_id and profile.user_id = ?) -?)  "+
                 "  and  "+
                 "    ( ( select distinct level.rating "+
                 "      from  "+database_name+"level, "+database_name+"profile "+
                 "      where level.id = profile.level_id "+
                 "      and profile.user_id = ?)+?) )) ";

        PreparedStatementSetter ps2 = new PreparedStatementSetter() {
        @Override   
        public void setValues(java.sql.PreparedStatement ps) throws SQLException {
            ps.setString(1, userid);
            ps.setInt(2, 1);
            ps.setString(3, userid);
            ps.setInt(4, 1);
        }

        };

        List<User> users = getJdbcTemplate().query(sql,ps2,new RowMapper<User>()
       {

              @Override
              public User mapRow(ResultSet rs, int rowNum) throws SQLException 
              {

                User user = new User();
                user.setUserid(rs.getString(1));
                user.setFirstName(rs.getString(2));
                user.setLastName(rs.getString(3));
                user.setRating( rs.getString(4));
                //user.setPhoto_file_path(rs.getString(5));
                return user;
              }});
        System.out.println(users.size());
      //  for(User user: users)
    //      System.out.println(user);
        return users;

      }

}

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java为每个请求提供一个DAO访问

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