基于Spring MVC的Web应用开发(八) - Convert

基于Spring MVC的Web应用开发(8) - Convert

本文介绍SpringMVC中的Convert，Convert是我认为的SpringMVC最吸引人，最优雅的特性，下面通过例子程序领略一下：

package org.springframework.samples.mvc.convert;

import java.util.Collection;
import java.util.Date;

import org.springframework.format.annotation.DateTimeFormat;
import org.springframework.format.annotation.DateTimeFormat.ISO;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.ResponseBody;

@Controller
@RequestMapping("/convert/*")
public class ConvertController {

	@RequestMapping("primitive")
	public @ResponseBody String primitive(@RequestParam Integer value) {
		return "Converted primitive " + value;
	}

	// requires Joda-Time on the classpath
	@RequestMapping("date/{value}")
	public @ResponseBody String date(@PathVariable @DateTimeFormat(iso=ISO.DATE) Date value) {
		return "Converted date " + value;
	}
	
	@RequestMapping("collection")
	public @ResponseBody String collection(@RequestParam Collection<Integer> values) {
		return "Converted collection " + values;
	}

	@RequestMapping("formattedCollection")
	public @ResponseBody String formattedCollection(@RequestParam @DateTimeFormat(iso=ISO.DATE) Collection<Date> values) {
		return "Converted formatted collection " + values;
	}

	@RequestMapping("bean")
	public @ResponseBody String bean(JavaBean bean) {
		return "Converted " + bean;
	}

	@RequestMapping("value")
	public @ResponseBody String valueObject(@RequestParam SocialSecurityNumber value) {
		return "Converted value object " + value;
	}

	@RequestMapping("custom")
	public @ResponseBody String customConverter(@RequestParam @MaskFormat("###-##-####") String value) {
		return "Converted '" + value + "' with a custom converter";
	}

}

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逐一方法看过来：

1.

	@RequestMapping("primitive")
	public @ResponseBody String primitive(@RequestParam Integer value) {
		return "Converted primitive " + value;
	}

@RequestParam自动获取URL提交的参数名为value的值并赋值到Integer value变量，

访问"http://localhost:8080/web/convert/primitive?value=1"

浏览器显示"Converted primitive 1"

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2.

	// requires Joda-Time on the classpath
	@RequestMapping("date/{value}")
	public @ResponseBody String date(@PathVariable @DateTimeFormat(iso=ISO.DATE) Date value) {
		return "Converted date " + value;
	}

@PathVariable自动获取URL路径中date/后面的值，判断该值是否满足ISO.DATE的类型（yyyy-MM-dd），最后将这个字符串转成Date value，

访问"http://localhost:8080/web/convert/date/2012-03-30"

浏览器显示"Converted date Fri Mar 30 00:00:00 CST 2012"

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3.

	@RequestMapping("collection")
	public @ResponseBody String collection(@RequestParam Collection<Integer> values) {
		return "Converted collection " + values;
	}

如果提交了同名参数的多个值（例如html的多选框），这些值会自动的封装到Collection<Integer> values里，

访问"http://localhost:8080/web/convert/collection?values=1&values=2"??

浏览器显示"Converted collection [1, 2]"

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4.

	@RequestMapping("formattedCollection")
	public @ResponseBody String formattedCollection(@RequestParam @DateTimeFormat(iso=ISO.DATE) Collection<Date> values) {
		return "Converted formatted collection " + values;
	}

访问"http://localhost:8080/web/convert/formattedCollection?values=2012-03-30&values=2012-12-25"

浏览器显示"Converted formatted collection [Fri Mar 30 00:00:00 CST 2012, Tue Dec 25 00:00:00 CST 2012]"

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以上说的都是convert简单类型，下面讲解如何convert自定义的Java类，写一个JavaBean类，该类有几个属性：

	private Integer primitive;
	
	@DateTimeFormat(iso=ISO.DATE)
	private Date date;

	@MaskFormat("(###) ###-####")
	private String masked;

	// list will auto-grow as its dereferenced e.g. list[0]=value
	private List<Integer> list;

	// annotation type conversion rule will be applied to each list element
	@DateTimeFormat(iso=ISO.DATE)
	private List<Date> formattedList;

	// map will auto-grow as its dereferenced e.g. map[key]=value
	private Map<Integer, String> map;

	// nested will be set when it is referenced e.g. nested.foo=value
	private NestedBean nested;

注意到该JavaBean还嵌套了一个自定义的Java类NestedBean，该类的属性为：

	private String foo;

	private List<NestedBean> list;
	
	private Map<String, NestedBean> map;

看一下详细用法：

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5.

访问"http://localhost:8080/web/convert/bean?primitive=1"

浏览器显示"Converted JavaBean primitive=1"

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6.

访问"http://localhost:8080/web/convert/bean?date=2012-03-30"

浏览器显示"Converted JavaBean date=Fri Mar 30 00:00:00 CST 2012"

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7.

访问"http://localhost:8080/web/convert/bean?masked=(123)-456-7890"

浏览器显示"Converted JavaBean masked=(123) 456-7890"

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8.

访问"http://localhost:8080/web/convert/bean?list[0]=1&list[1]=2"

浏览器显示"Converted JavaBean list=[1, 2]"

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9.

访问"http://localhost:8080/web/convert/bean?formattedList[0]=2012-03-30&formattedList[1]=2012-12-25"

浏览器显示"Converted JavaBean formattedList=[Fri Mar 30 00:00:00 CST 2012, Tue Dec 25 00:00:00 CST 2012]"

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10.

访问"http://localhost:8080/web/convert/bean?map[1]=a&map[2]=b"

浏览器显示"Converted JavaBean map={1=a, 2=b}"

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11.

访问"http://localhost:8080/web/convert/bean?nested.foo=stephansun"

浏览器显示"Converted JavaBean nested=NestedBean foo=stephansun"

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12.

访问"http://localhost:8080/web/convert/bean?nested.list[0].foo=stephansun"

浏览器显示"Converted JavaBean nested=NestedBean list=[NestedBean foo=stephansun]"

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13.

访问"http://localhost:8080/web/convert/bean?nested.map[1].foo=stephansun"

浏览器显示"Converted JavaBean nested=NestedBean map={1=NestedBean foo=stephansun}"

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14.

访问"http://localhost:8080/web/convert/value?value=1"

浏览器显示"Converted value object SocialSecurityNumber [value=1]"

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15.

访问"http://localhost:8080/web/convert/custom?value=ab-cd-efgh"

浏览器显示"Converted 'ab-cd-efgh' with a custom converter"

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