[Spring MVC] - 从数据库读取MessageSource

Spring MVC中使用MessageSource默认是写在properties文件当中，以支持国际化。

但很多时候我们需要把数据写到数据库当中，而不是在properties文件当中，以方便日常维护。

1、先看Spring配置

    <!-- 默认的注解映射的支持 -->
    <mvc:annotation-driven validator="validator" conversion-service="conversionService" />

    <!-- 资源文件 -->
    <bean id="propertiesMessageSource" class="org.springframework.context.support.ResourceBundleMessageSource">
        <property name="basenames">
            <list>
                <value>resource</value>
                <value>validation</value>
            </list>
        </property>
    </bean>
    <bean id="databaseMessageSource" class="com.obs2.util.MessageResource">
        <property name="parentMessageSource" ref="propertiesMessageSource"/>
    </bean>
    <bean id="messageInterpolator" class="com.obs2.util.MessageResourceInterpolator">
        <property name="messageResource" ref="databaseMessageSource"/>
    </bean>
    <!-- 验证器 -->
    <bean id="validator" class="org.springframework.validation.beanvalidation.LocalValidatorFactoryBean">
        <property name="messageInterpolator" ref="messageInterpolator"/>
    </bean>

这里定义了一个propertiesMessageSource，一个databaseMessageSourcer，和一个messageInterpolator。

propertiesMessageSource用于读取properties文件

databaseMessageSourcer用于读取数据库的数据配置，其中，有一个属性设置它的父MessageSource为propertiesMessageSource。意思是如果数据库找不到对应的数据，到properties文件当中查找。

messageInterpolator是个拦截器。

2、数据库的POJO定义：

package com.obs2.dao.impl.bean;

import java.io.Serializable;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;

@Entity
@SuppressWarnings("serial")
@Table(name="resource")
public class Resource implements Serializable {

    @Id
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    @Column(name="resource_id")
    private long resourceId;

    @Column(name="name", length=50, nullable=false)
    private String name;

    @Column(name="text", length=1000, nullable=false)
    private String text;

    @Column(name="language", length=5, nullable=false)
    private String language;

    public long getResourceId() {
        return resourceId;
    }
    public void setResourceId(long resourceId) {
        this.resourceId = resourceId;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getText() {
        return text;
    }
    public void setText(String text) {
        this.text = text;
    }
    public String getLanguage() {
        return language;
    }
    public void setLanguage(String language) {
        this.language = language;
    }

}

定义了一张表[resource]，字段有：[resource_id]、[name]、[text]、[language]

具体的DAO、Service操作方法这里忽略不写了。

3、读取数据库的MessageResource类

package com.obs2.util;

import java.text.MessageFormat;
import java.util.HashMap;
import java.util.List;
import java.util.Locale;
import java.util.Map;

import javax.annotation.Resource;

import org.springframework.context.ResourceLoaderAware;
import org.springframework.context.support.AbstractMessageSource;
import org.springframework.core.io.DefaultResourceLoader;
import org.springframework.core.io.ResourceLoader;

import com.obs2.service.ResourceService;

/**
 * 取得资源数据
 * @author Robin
 *
 */
public class MessageResource extends AbstractMessageSource implements ResourceLoaderAware {

    @SuppressWarnings("unused")
    private ResourceLoader resourceLoader;

    @Resource
    private ResourceService resourceService;

    /**
     * Map切分字符
     */
    protected final String MAP_SPLIT_CODE = "|";

    protected final String DB_SPLIT_CODE = "_";

    private final Map<String, String> properties = new HashMap<String, String>();

    public MessageResource() {
//        reload();
    }

    public void reload() {
        properties.clear();
        properties.putAll(loadTexts());
    }

    protected Map<String, String> loadTexts() {
        Map<String, String> mapResource = new HashMap<String, String>();
        List<com.obs2.service.bean.Resource> resources = resourceService.findAll();
        for (com.obs2.service.bean.Resource item : resources) {
            String code = item.getName() + MAP_SPLIT_CODE + item.getLanguage();
            mapResource.put(code, item.getText());
        }
        return mapResource;
    }

    private String getText(String code, Locale locale) {
        String localeCode = locale.getLanguage() + DB_SPLIT_CODE + locale.getCountry();
        String key = code + MAP_SPLIT_CODE + localeCode;
        String localeText = properties.get(key);
        String resourceText = code;

        if(localeText != null) {
            resourceText = localeText;
        }
        else {
            localeCode = Locale.ENGLISH.getLanguage();
            key = code + MAP_SPLIT_CODE + localeCode;
            localeText = properties.get(key);
            if(localeText != null) {
                resourceText = localeText;
            }
            else {
                try {
                    if(getParentMessageSource() != null) {
                        resourceText = getParentMessageSource().getMessage(code, null, locale);
                    }
                } catch (Exception e) {
                    logger.error("Cannot find message with code: " + code);
                }
            }
        }
        return resourceText;
    }

    @Override
    public void setResourceLoader(ResourceLoader resourceLoader) {
        this.resourceLoader = (resourceLoader != null ? resourceLoader : new DefaultResourceLoader());
    }

    @Override
    protected MessageFormat resolveCode(String code, Locale locale) {
        String msg = getText(code, locale);
        MessageFormat result = createMessageFormat(msg, locale);
        return result;
    }

    @Override
    protected String resolveCodeWithoutArguments(String code, Locale locale) {
        String result = getText(code, locale);
        return result;
    }

}

主要是重载AbstractMessageSource和ResourceLoaderAware，以实现Spring MVC的MessageSource国际化调用。

类中的reload()方法，我把它写到了一个ServletListener当中，让项目启动时，自动加载数据到static的map中。

4、这是Listener:

package com.obs2.util;

import javax.servlet.ServletContext;
import javax.servlet.ServletContextAttributeEvent;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import javax.servlet.http.HttpSessionEvent;

import org.springframework.web.context.WebApplicationContext;
import org.springframework.web.context.support.WebApplicationContextUtils;

/**
 * 系统启动监听
 * @author Robin
 *
 */
public class SystemListener implements ServletContextListener {

    /**
     * context初始化时激发
     */
    @Override
    public void contextInitialized(ServletContextEvent e) {
        //------------------------------------------------------------
        // 取得ServletContext
        //------------------------------------------------------------
        ServletContext context = e.getServletContext();
        WebApplicationContext applicationContext  = WebApplicationContextUtils .getWebApplicationContext(context);

        //------------------------------------------------------------
        // 设置国际化多语言
        //------------------------------------------------------------
        MessageResource messageSource = applicationContext.getBean(MessageResource.class);
        messageSource.reload();
    }

    /**
     * context删除时激发
     */
    @Override
    public void contextDestroyed(ServletContextEvent e) {
    }

    /**
     * 创建一个 session时激发
     * @param e
     */
    public void sessionCreated(HttpSessionEvent e) {
    }

    /**
     * 当一个 session失效时激发
     * @param e
     */
    public void sessionDestroyed(HttpSessionEvent e) {
    }

    /**
     * 设置 context的属性，它将激发attributeReplaced或attributeAdded方法
     * @param e
     */
    public void setContext(HttpSessionEvent e) {
    }

    /**
     * 增加一个新的属性时激发
     * @param e
     */
    public void attributeAdded(ServletContextAttributeEvent e) {
    }

    /**
     * 删除一个新的属性时激发
     * @param e
     */
    public void attributeRemoved(ServletContextAttributeEvent e) {
    }

    /**
     * 属性被替代时激发
     * @param e
     */
    public void attributeReplaced(ServletContextAttributeEvent e) {
    }

}

当然了，Listener需要加入到web.xml当中：

    <!-- 系统启动监听 -->
    <listener>
        <listener-class>com.obs2.util.SystemListener</listener-class>
    </listener>

4、Interceptor拦截器

package com.obs2.util;

import java.text.MessageFormat;
import java.util.Iterator;
import java.util.Locale;
import java.util.Map;
import java.util.Map.Entry;

import javax.annotation.Resource;
import javax.validation.MessageInterpolator;

import org.springframework.binding.message.MessageBuilder;

/**
 * 拦截Annotation验证信息
 * @author Robin
 *
 */
public class MessageResourceInterpolator implements MessageInterpolator {

    @Resource
    private MessageResource messageResource;
    public void setMessageResource(MessageResource messageResource) {
        this.messageResource = messageResource;
    }

    @Override
    public String interpolate(String messageTemplate, Context context) {

        String messageTemp = null;
        if(messageTemplate.startsWith("{") && messageTemplate.endsWith("}")) {
            messageTemp = messageTemplate.substring(1, messageTemplate.length() - 1);
        }
        else {
            return messageTemplate;
        }

        String[] params = (String[]) context.getConstraintDescriptor().getAttributes().get("params");

        MessageBuilder builder = new MessageBuilder().code(messageTemp);
        if (params != null) {
            for (String param : params) {
                builder = builder.arg(param);
            }
        }

        String result = builder.build().resolveMessage(messageResource, Locale.ENGLISH).getText();
        return result;
    }

    @Override
    public String interpolate(String messageTemplate, Context context, Locale locale) {

        String messageTemp = null;
        if(messageTemplate.startsWith("{") && messageTemplate.endsWith("}")) {
            messageTemp = messageTemplate.substring(1, messageTemplate.length() - 1);
        }
        else {
            return messageTemplate;
        }

        String[] params = (String[]) context.getConstraintDescriptor().getAttributes().get("params");

        MessageBuilder builder = new MessageBuilder().code(messageTemp);
        if (params != null) {
            builder = builder.args(params);
        }

        String result = builder.build().resolveMessage(messageResource, locale).getText();
        return result;
    }

}

事实上，不使用拦截器，上面的数据库MessageSource类已经可以工作了。但在使用hibernate的Annotation的validator时，不加入拦截器，是不行的，它不会触发。

这类里调用了一个jar包：spring-binding-2.3.1.RELEASE.jar

自行上网搜搜下载。

一切完成，测试下，写一个domain entity:

package com.obs2.controller.bean;

import javax.validation.constraints.Min;

import org.hibernate.validator.constraints.NotEmpty;

import com.obs2.controller.validator.UserName;

public class Account {

    @UserName(format="^[\\w_]+$", message="{valid.userName}", min=6, max=30)
    private String userName;
    @NotEmpty(message="{valid.required}")
    private String password;
    @Min(value=18, message="{valid.ageMin}")
    private int age;

    public String getUserName() {
        return userName;
    }
    public void setUserName(String userName) {
        this.userName = userName;
    }
    public String getPassword() {
        return password;
    }
    public void setPassword(String password) {
        this.password = password;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }

}

写一个简单的view（这里使用的是freemarker）

<#assign c=JspTaglibs["http://java.sun.com/jsp/jstl/core"] />
<#assign fmt=JspTaglibs["http://java.sun.com/jsp/jstl/fmt"] />
<#assign fn=JspTaglibs["http://java.sun.com/jsp/jstl/functions"] />
<#assign st=JspTaglibs["http://www.springframework.org/tags"] />
<#assign form=JspTaglibs["http://www.springframework.org/tags/form"] />
<head>
    <title>Login</title>
</head>

<body>
    <@form.form action="${request.contextPath}/passport/login" method="post" modelAttribute="account">
    User name:<@form.input path="userName"/><@form.errors path="userName"/><br/>
    Password:<@form.password path="password"/><@form.errors path="password" /><br/>
    Age:<@form.input path="age"/><@form.errors path="age" /><br/>
    <input type="submit" value="Login" />
    </@form.form>
</body>

将看到：

这种方法还有一个小BUG，就是在使用annotation validator时，如果使用了替换符，似乎不起作用。暂时没研究出来，谁搞出来了，麻烦留个言提示下。so thx.

代码中直接调用，可以这样写：

resource.getMessage("valid.ageMin", new Object[]{"age",18}, request.getLocale())