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";}}?
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]=valueprivate 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]=valueprivate Map<Integer, String> map;// nested will be set when it is referenced e.g. nested.foo=valueprivate 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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