6.转换器和格式化-白红宇

6.转换器和格式化

阅读量：5787 次

发布时间：2019-06-18

本文共 8516 字，大约阅读时间需要 28 分钟。

1.Converter:转换器：可以在应用程序的任意层中使用

2.Formatter格式化：专门为Web设计

二者都可以将一种对象转换成另一种对象类型

1.Converter

必须实现org.springframework.core.convert.converter.Converter

public interface Converter<S,T>

S:是源类型

T：是目标类型

在类Body中，需要编写一个来自Converter接口的convert方法实现。

T convert(S source);

1 package app06a.converter; 2  3 import java.text.ParseException; 4 import java.text.SimpleDateFormat; 5 import java.util.Date; 6  7 import org.springframework.core.convert.converter.Converter; 8  9 public class StringToDateConverter implements Converter
     
       {10 11     private String datePattern;12 13     public StringToDateConverter(String datePattern) {14         this.datePattern = datePattern;15     }16 17     @Override18     public Date convert(String s) {19         try {20             SimpleDateFormat dateFormat = new SimpleDateFormat(datePattern);21             dateFormat.setLenient(false);22             return dateFormat.parse(s);23         } catch (ParseException e) {24             // the error message will be displayed when using 
      
       25             throw new IllegalArgumentException(26                     "invalid date format. Please use this pattern\""27                             + datePattern + "\"");28         }29     }30 }

为了使用SpringMVC应用程序中定制Converter

需要在Spring MVC配置文件中编写converterService bean

Bean的类名称为org.springframework.context.support.ConversionServiceFactoryBean

这个Bean必须包含一个converts属性，它将列出要在应用程序中使用所有定制的Converter

要给<mvc:annotation-driven conversion-service="conversionService"/>

conversion-service属性赋bean名称

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Employee类

1 package app06a.domain; 2  3 import java.io.Serializable; 4 import java.util.Date; 5  6 public class Employee implements Serializable { 7     private static final long serialVersionUID = -908L; 8  9     private long id;10     private String firstName;11     private String lastName;12     private Date birthDate;13     private int salaryLevel;14 15     public long getId() {16         return id;17     }18 19     public void setId(long id) {20         this.id = id;21     }22 23     public String getFirstName() {24         return firstName;25     }26 27     public void setFirstName(String firstName) {28         this.firstName = firstName;29     }30 31     public String getLastName() {32         return lastName;33     }34 35     public void setLastName(String lastName) {36         this.lastName = lastName;37     }38 39     public Date getBirthDate() {40         return birthDate;41     }42 43     public void setBirthDate(Date birthDate) {44         this.birthDate = birthDate;45     }46 47     public int getSalaryLevel() {48         return salaryLevel;49     }50 51     public void setSalaryLevel(int salaryLevel) {52         this.salaryLevel = salaryLevel;53     }54 55 }

Controller

有了StringToDateConverter converter，就不需要劳驾

controller类将字符串转换成日期了

1 package app06a.controller; 2  3 import org.apache.commons.logging.Log; 4 import org.apache.commons.logging.LogFactory; 5 import org.springframework.ui.Model; 6 import org.springframework.validation.BindingResult; 7 import org.springframework.validation.FieldError; 8 import org.springframework.web.bind.annotation.ModelAttribute; 9 import org.springframework.web.bind.annotation.RequestMapping;10 11 import app06a.domain.Employee;12 13 @org.springframework.stereotype.Controller14 15 public class EmployeeController {16     17     private static final Log logger = LogFactory.getLog(ProductController.class);18     19     @RequestMapping(value="employee_input")20     public String inputEmployee(Model model) {21         model.addAttribute(new Employee());22         return "EmployeeForm";23     }24 25     @RequestMapping(value="employee_save")26     public String saveEmployee(@ModelAttribute Employee employee, BindingResult bindingResult,27             Model model) {28         if (bindingResult.hasErrors()) {29             FieldError fieldError = bindingResult.getFieldError();30             logger.info("Code:" + fieldError.getCode() 31                     + ", field:" + fieldError.getField());32             return "EmployeeForm";33         }34         35         // save employee here36         37         model.addAttribute("employee", employee);38         return "EmployeeDetails";39     }40 }

1 <%@ taglib prefix="form" uri="http://www.springframework.org/tags/form" %> 2 <%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %> 3  4  5  6 Add Employee Form 7  8  9 10 11 
     
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2.Formatter

Formatter也是将一种类型转换成另一种类型

但Formatter源类型必须是一个String，而Converter则适用于任意的源类型

为了创建Formmatter要编写一个org.springframework.format.Formatter接口的java类

public interface Formatter<T>

这里T表示输入字符串要转换的目标类型

T parse(String text,java.util.Locale.locale);

String print(T object,java.util.Locale.locale);

1 package app06b.formatter; 2  3 import java.text.ParseException; 4 import java.text.SimpleDateFormat; 5 import java.util.Date; 6 import java.util.Locale; 7  8 import org.springframework.format.Formatter; 9 10 public class DateFormatter implements Formatter
     
       {11 12     private String datePattern;13     private SimpleDateFormat dateFormat;14 15     public DateFormatter(String datePattern) {16         System.out.println("DateFormatter()5b========");17         this.datePattern = datePattern;18         dateFormat = new SimpleDateFormat(datePattern);19         dateFormat.setLenient(false);20     }21 22     @Override23     public String print(Date date, Locale locale) {24         return dateFormat.format(date);25     }26 27     @Override28     public Date parse(String s, Locale locale) throws ParseException {29         try {30             return dateFormat.parse(s);31         } catch (ParseException e) {32             // the error message will be displayed when using 
      
       33             throw new IllegalArgumentException(34                     "invalid date format. Please use this pattern\""35                             + datePattern + "\"");36         }37     }38 }

为了在String MVC应用程序中使用Formmatter，需要利用conversionService bean

进行注册。

bean的类名称必须为org.springframework.format.support.FormattingConversionServiceFactoryBean.

还需要给Formatter添加一个<context:component-scan base-package="app06b.formatter" />

3.用Registrar注册Formmatter

注册Formmatter的另一个方法是Registrar

1 public class MyFormmatterRegistrar implements FormatterRegistrar{ 2      3    private String datePattern; 4    public MyFormmatterRegistrar(String datePattern){ 5          this.datePattern = datePattern; 6     } 7  8    public void registerFormatters(FormatterRegistry resgitry){ 9        resgitry.addFormatter(new DateFormatter(datePattern));      10    }11 }

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