模板方法精讲

package pattern.template.entity;
import java.io.Serializable;
public class Member implements Serializable {
    private String username;
    private String password;
    private String nickName;
    private int age;
    private String addr;

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public String getNickName() {
        return nickName;
    }

    public void setNickName(String nickName) {
        this.nickName = nickName;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public String getAddr() {
        return addr;
    }

    public void setAddr(String addr) {
        this.addr = addr;
    }
}

package pattern.template.dao;
import pattern.template.JdbcTemplate;
import pattern.template.RowMapper;
import pattern.template.entity.Member;
import java.sql.ResultSet;
import java.util.List;

public class MemberDao {

    //像是静态代理
    private JdbcTemplate JdbcTemplate=new JdbcTemplate(null);
    public List<?> query(){
        String sql="select * from t_member";
       return JdbcTemplate.executeQuery(sql,new RowMapper<Member>(){
           @Override
           public Member mapRow(ResultSet rs, int rowNum) throws Exception{
               Member member=new Member();
               member.setUsername(rs.getString("username"));
               member.setPassword(rs.getString("password"));
               member.setAge(rs.getInt("username"));
               member.setAddr(rs.getString("addr"));
               return member;
           }
       },null);
   }
}

package pattern.template;
import javax.sql.DataSource;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.util.ArrayList;
import java.util.List;
public class JdbcTemplate {
    private DataSource dataSource;
    public JdbcTemplate(DataSource dataSource){
       this.dataSource=dataSource;
    }

    private Connection getConnection() throws Exception{
        return this.dataSource.getConnection();
    }

    private ResultSet executeQuery(PreparedStatement pstmt,Object[] values) throws Exception{
        for (int i=0;i<values.length;i++){
          pstmt.setObject(i,values[i]);
        }
        return pstmt.executeQuery();
    }

    private PreparedStatement createPreparedStatement(Connection conn,String sql) throws Exception{
        return conn.prepareStatement(sql);
    }

    private void closeStatement(PreparedStatement pstmt) throws Exception{
      pstmt.close();
    }

    private void closeResultSet(ResultSet rs) throws Exception{
       rs.close();
    }

    private void closeConnection(Connection conn) throws Exception{
       //一般不会关闭
    }

    private List<?> parseResultSet(ResultSet rs,RowMapper rowMapper) throws Exception{
        List<Object> result=new ArrayList<>();
            int rowNum=1;
            while (rs.next()){
                result.add(rowMapper.mapRow(rs,rowNum++));
            }
            return result;
    }

    public List<?> executeQuery(String sql,RowMapper<?> rowMapper,Object[] values)  {
        try {
            //1、获取连接
             Connection conn=this.getConnection();
            //2、创建语句集
            PreparedStatement pstmt=this.createPreparedStatement(conn,sql);
            //3、执行语句集,并且获得结果集
            ResultSet rs=this.executeQuery(pstmt,values);
            //4、解析语句集
            List<?> result=this.parseResultSet(rs,rowMapper);
            //5、关闭结果集
            this.closeResultSet(rs);
            //6、关闭语句集
            this.closeStatement(pstmt);
            //7、关闭连接
            this.closeConnection(conn);
         return result;
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

    //public Object processResult(ResultSet rs,int rowNum) throws SQLException;

}

package pattern.template;
import java.sql.ResultSet;
public interface RowMapper<T> {

    public T mapRow(ResultSet rs,int rowNum) throws Exception;

}

package pattern.template;
import pattern.template.dao.MemberDao;
public class MemberDaoTest {
    public static void main(String[] args) {
        MemberDao memberDao = new MemberDao();
        memberDao.query();
    }
}