JAVA 入门12 HttpServlet

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最新推荐文章于 2023-09-24 15:17:16 发布

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分类专栏： Java基础

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本文介绍了一个使用 Java Servlet 处理 HTTP 请求的示例，包括无参数和有参数两种情况，并展示了如何利用 FastJSON 将查询结果转换为 JSON 格式返回。

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效果展示

无参
有参

实现步骤

导包

<dependencies>
  <!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>8.0.15</version>
</dependency>
  
  <!-- https://mvnrepository.com/artifact/javax.servlet/javax.servlet-api -->
<dependency>
    <groupId>javax.servlet</groupId>
    <artifactId>javax.servlet-api</artifactId>
    <version>4.0.1</version>
    <scope>provided</scope>
</dependency>
  
  <!-- https://mvnrepository.com/artifact/com.alibaba/fastjson -->
<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>fastjson</artifactId>
    <version>1.2.47</version>
</dependency>
  </dependencies>

创建 servlet -无参

package com.base.day10;

import java.io.IOException;
import java.util.ArrayList;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.alibaba.fastjson.JSONObject;
import com.base.day9.ProductService;
/**
 * Servlet implementation class StudentServlet
 */
public class StudentServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public StudentServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		ProductService ps=new ProductService();
		ArrayList ls=ps.selectAll();
		//对象，转json格式字符串
		String rs=JSONObject.toJSONString(ls);
		//解决中文乱码问题
		response.setCharacterEncoding("utf-8");
		response.setContentType("text/html;charset=utf-8");
		response.getWriter().append(rs);
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(request, response);
	}

}

有参 servlet

package com.base.day10;

import java.io.IOException;
import java.util.ArrayList;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.alibaba.fastjson.JSONObject;
import com.base.day9.Product;
import com.base.day9.ProductService;

/**
 * Servlet implementation class StudentServlet2
 */
public class StudentServlet2 extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public StudentServlet2() {
        super();
        // TODO Auto-generated constructor stub
    }

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		//取出请求中的参数
		String productname=request.getParameter("pname");
		
		ProductService ps=new ProductService();
		Product p1=ps.findByName(productname);
		//对象，转json格式字符串
		String rs=JSONObject.toJSONString(p1);
		response.setCharacterEncoding("utf-8");
		response.setContentType("text/html;charset=utf-8");
		response.getWriter().append(rs);
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(request, response);
	}

}