JavaEE-博客系统2（功能设计）

本部分内容：实现博客列表页；web程序问题的分析方法；实现博客详情页；

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该部分的代码如下：

@WebServlet("/blog")
public class BlogServlet extends HttpServlet {//Jackson ObjectMapper类(com.fasterxml.jackson.databind.ObjectMapper)解析JSON工具////序列化：      Java对象生成Json////反序列化：  Json解析为Java对象private ObjectMapper objectMapper=new ObjectMapper();@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {BlogDao blogDao=new BlogDao();List<Blog> blogs =blogDao.getblogs();String respJson=objectMapper.writeValueAsString(blogs);resp.setContentType("application/json;charset=utf8");resp.getWriter().write(respJson);}

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上述过程中的一些疑问

这部分的运行效果图如下：

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修改后的BlogServlet.java代码如下：

package api;import Dao.Blog;
import Dao.BlogDao;
import com.fasterxml.jackson.databind.ObjectMapper;import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.List;/*** Created with IntelliJ IDEA.* Description:* User: Home-pc* Date: 2023-10-28* Time: 16:56*/
@WebServlet("/blog")
public class BlogServlet extends HttpServlet {//Jackson ObjectMapper类(com.fasterxml.jackson.databind.ObjectMapper)解析JSON工具////序列化：      Java对象生成Json////反序列化：  Json解析为Java对象private ObjectMapper objectMapper=new ObjectMapper();@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {BlogDao blogDao=new BlogDao();//尝试获取blogId这个参数，根据是否能获取到这个参数，将其进行分支String blogId=req.getParameter("blogId");if(blogId==null){//说明此处是需要获取博客列表List<Blog> blogs =blogDao.getblogs();String respJson=objectMapper.writeValueAsString(blogs);resp.setContentType("application/json;charset=utf8");resp.getWriter().write(respJson);}else{//说明此处要获得某篇博客的详情页 获取一篇博客Blog blog=blogDao.getblog(Integer.parseInt(blogId));//如果该篇博客不存在，那么此时的blog==nullif(blog==null){blog=new Blog();}String respJson=objectMapper.writeValueAsString(blog);resp.setContentType("application/json;charset=utf8");resp.getWriter().write(respJson);}}
}