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我正在尝试将一个文本字段(一个以逗号分隔的标签名称列表,标签是我的域对象)绑定到一个变量,该变量是一个标签对象列表,位于另一个名为 Expense 的域对象中。因此,用户在表单中输入费用项目的标签列表,这将绑定到费用域对象中的标签项目集合。到目前为止,我在代码中所做的是:

我的jsp文件有:

<tr>
  <td>Tags</td>
  <td><form:input path="tags" type="text" name="tags" id="tags_formfield" /></td>
</tr>

我的域对象有:

    //bi-directional many-to-many association to Tag
@ManyToMany()
@JoinTable(name="EXPENSES_X_TAGS",
joinColumns= @JoinColumn(name="EXPENSE_ID", referencedColumnName="ID"), 
inverseJoinColumns= @JoinColumn(name="TAG_ID", referencedColumnName="ID"))

private List<Tag> tags;

我的控制器有:

@InitBinder
public void initBinder(WebDataBinder binder) {
    binder.registerCustomEditor(List.class, new TagsEditor());
}

我也试过:

@InitBinder
public void initBinder(WebDataBinder binder) {
    binder.registerCustomEditor(Tag.class, new TagsEditor());
}

而我的属性编辑器是:
package com.transience.sandbox.converters;导入 java.beans.PropertyEditorSupport;导入 java.util.ArrayList;导入 java.util.List;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.beans.factory.annotation.Autowired;

import com.transience.sandbox.domain.Tag;
import com.transience.sandbox.services.ITagService;

public class TagsEditor extends PropertyEditorSupport {

    @Autowired
    ITagService tagService; 
    protected final Log logger = LogFactory.getLog(getClass());

    @Override
    // Converts a comma separated String of tagNames to a List<Tag> (when submitting form)
    public void setAsText(String stringOfTagNames) {
        List<Tag> tags = null;

        String[] tagNames = stringOfTagNames.split(",");
        logger.info("Looping through tagNames now...");
        for(String tagName : tagNames) {
            logger.info("tag name: " + tagName);
            Tag tag = tagService.findByTagName(tagName);
            tags.add(tag);
        }       
        logger.info("Trying to setValue now...");
        this.setValue(tags);
        logger.info("Value of List of Tags set successfully...");
    }




}

但我在提交表单时遇到以下异常:

Error 500--Internal Server Error

    org.springframework.validation.BindException: org.springframework.validation.BeanPropertyBindingResult: 1 errors
    Field error in object 'expense' on field 'tags': rejected value [booze,lunch]; codes [methodInvocation.expense.tags,methodInvocation.tags,methodInvocation.java.util.List,methodInvocation]; arguments [org.springframework.context.support.DefaultMessageSourceResolvable: codes [expense.tags,tags]; arguments []; default message [tags]]; default message [Property 'tags' threw exception; nested exception is java.lang.NullPointerException]
        at org.springframework.web.method.annotation.ModelAttributeMethodProcessor.resolveArgument(ModelAttributeMethodProcessor.java:110)
        at org.springframework.web.method.support.HandlerMethodArgumentResolverComposite.resolveArgument(HandlerMethodArgumentResolverComposite.java:74)
        at org.springframework.web.method.support.InvocableHandlerMethod.getMethodArgumentValues(InvocableHandlerMethod.java:155)
        at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:117)
        at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:96)
        at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:617)
        at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:578)
        at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:80)
        at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:900)
        at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:827)
        at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:882)

我很确定我在做一些根本不正确的事情,但我做错了什么?我知道转换器方法,但我很想知道如何使用 PropertyEditors 来完成

谢谢,桑杰

4

1 回答 1

2

我通过添加valueOf(String)到域对象来解决它(toString 对于向后转换也很重要)。不知何故,Spring 已经能够将 csv 转换为List. 在这里找到答案:如何将逗号分隔的字符串绑定到 Spring 形式的 Java 集合(列表)?

于 2014-01-12T00:31:27.957 回答