Question

我的RequestParam存在很大问题。我读了一些其他问题同样的问题，但我检查了语法一百次，我不知道我的代码有什么问题。我是春天的新人，如果有人能查看我的代码并帮我找出错误，那将是非常好的。

我有一个带有表单标记的jsp文件。在该形式中，用户可以选择他想要创建的图表类型。我的jsp文件：

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Insert title here</title>
</head>
<body>
<form   action="piechart" method="get">
<input type="radio" name="pieChart" value="pie">pie<br>
<input type="radio" name="barChart" value="bar">bar<br>
<input type="submit" value="Submit">
</form> 

<img src="/piechart" />
</body>
</html>

我的控制器看起来像这样：

package net.codejava.springmvc;

import java.awt.Color;
import java.awt.Font;
import java.io.IOException;

import javax.servlet.http.HttpServletResponse;

import org.jfree.chart.ChartFactory;
import org.jfree.chart.ChartUtilities;
import org.jfree.chart.JFreeChart;
import org.jfree.chart.plot.PiePlot;
import org.jfree.data.general.DefaultPieDataset;
import org.jfree.data.general.PieDataset;
import org.jfree.util.Rotation;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;


@Controller
public class ResultController {


      private double value1 = 20.0;
      private double value2 = 20.0;
      private double value3 = 20.0;
      private double value4 = 20.0;
      private double value5 = 20.0;

      private String answer1 = "very good: " + value1 + "%";
      private String answer2 = "good: " + value2 + "%";
      private String answer3 = "bad: " + value3 + "%";
      private String answer4 = "very bad: " + value4 + "%";
      private String answer5 ="no answer: " + value5 + "%";

      @RequestMapping(value="/result", method= RequestMethod.GET)
      public String test() {
          return "jsp/result/pieChart";
      }

    @RequestMapping(value= "/piechart", method= RequestMethod.GET)
    public void createChart(@RequestParam("pie") String pie, @RequestParam("bar") String bar, HttpServletResponse response) {
        response.setContentType("image/png");
        PieDataset pieDataset = createDataset();
        JFreeChart pieChart = createChart(pieDataset, "Question");
        try {
            ChartUtilities.writeChartAsPNG(response.getOutputStream(), pieChart, 750, 400);
        } catch(IOException ex){
            ex.printStackTrace();
        }

    }
    /** * set Data*/

    public  PieDataset createDataset() {
        DefaultPieDataset result = new DefaultPieDataset();
        result.setValue(answer1, 20);
        result.setValue(answer2, 20);
        result.setValue(answer3, 20);
        result.setValue(answer4, 20);
        result.setValue(answer5, 20 );
        return result;

    }


/** * Creates a chart */

    @SuppressWarnings("deprecation")
    public JFreeChart createChart(PieDataset dataset, String title) {

        JFreeChart chart = ChartFactory.createPieChart(title,   
            dataset,                
            true,                   
            true,
            false);

        PiePlot plot = (PiePlot) chart.getPlot();
        plot.setStartAngle(290); 
        plot.setDirection(Rotation.CLOCKWISE);
        plot.setForegroundAlpha(0.9f);
        plot.setLabelBackgroundPaint(Color.white);
        plot.setBackgroundPaint(Color.LIGHT_GRAY);
        plot.setLabelFont(new Font("SansSerif", Font.ITALIC, 12));
        plot.setLabelLinksVisible(true);
        plot.setBackgroundPaint(null);
        plot.setInteriorGap(0.04);
        plot.setOutlineVisible(true);
        Color[] colors = {new Color(153,204,255), new Color(153,153,255), new Color(204,153,255), new Color(255,153,255), new Color(255,153,204)}; 
        for (int i = 0; i < 5; i++) {
            plot.setSectionPaint(i, colors[i]);
        }



        return chart;


    }

}

目前只能创建一个饼图。我选择radiobutton后，@ RequestParam会显示我的饼图，我会很高兴。

谢谢：）

Answer 1

您需要更改@RequestParam中使用的名称，以反映您在表单中使用的名称。

public void createChart(@RequestParam(value ="pieChart", required = false) String pie, @RequestParam(value = "barChart", required = false) String bar, HttpServletResponse response)

由于浏览器不允许选择两个无线电，我们需要向两者添加required = false。

在createChart内，你需要确保至少有一个参数被填充

spring mvc @RequestParam客户端发送的请求在语法上是不正确的

1 个答案: