Java 如何使用Jersey将嵌套列表封送为JSON？我得到一个空数组或一个包含数组的单元素字典数组

我正在从事一个项目，该项目使用Jersey将对象转换为JSON。我希望能够写出嵌套列表，如下所示：

{"data":[["one", "two", "three"], ["a", "b", "c"]]}

我要转换的对象首先表示为数据，我认为Jersey会做正确的事情。以上内容作为空值列表输出：

{"data":[null, null]}

在了解到嵌套对象需要包装后，我尝试了以下操作：

@XmlRootElement(name = "foo")
@XmlType(propOrder = {"data"})
public class Foo
{
    private Collection<FooData> data = new LinkedList<FooData>();

    @XmlElement(name = "data")
    public Collection<FooData> getData()
    {
        return data;
    }

    public void addData(Collection data)
    {
        FooData d = new FooData();
        for(Object o: data)
        {
            d.getData().add(o == null ? (String)o : o.toString());
        }
        this.data.add(d);
    }

    @XmlRootElement(name = "FooData")
    public static class FooData
    {
        private Collection<String> data = new LinkedList<String>();

        @XmlElement
        public Collection<String> getData()
        {
            return data;
        }
    }
}

我希望第一个数据是一个列表列表，而不是一个元素字典列表。我如何做到这一点

以下是我的JAXBContentResolver：

@Provider
public class JAXBContextResolver implements ContextResolver<JAXBContext>
{
    private JAXBContext context;
    private Set<Class<?>> types;

    // Only parent classes are required here. Nested classes are implicit.
    protected Class<?>[] classTypes = new Class[] {Foo.class};

    protected Set<String> jsonArray = new HashSet<String>(1) {
        {
            add("data");
        }
    };

    public JAXBContextResolver() throws Exception
    {        
        Map<String, Object> props = new HashMap<String, Object>();
        props.put(JSONJAXBContext.JSON_NOTATION, JSONJAXBContext.JSONNotation.MAPPED);
        props.put(JSONJAXBContext.JSON_ROOT_UNWRAPPING, Boolean.TRUE);
        props.put(JSONJAXBContext.JSON_ARRAYS, jsonArray);
        this.types = new HashSet<Class<?>>(Arrays.asList(classTypes));
        this.context = new JSONJAXBContext(classTyes, props);
    }

    public JAXBContext getContext(Class<?> objectType)
    {
        return (types.contains(objectType)) ? context : null;
    }
}

@Provider
公共类JAXBContextResolver实现ContextResolver
{
私有JAXBContext上下文；
私有集[]类类型=新类[]{Foo.Class}；
受保护集jsonArray=新哈希集（1）{
{
添加（“数据”）；
}
};
公共JAXBContextResolver（）引发异常
{        
Map props=newhashmap（）；
put（JSONJAXBContext.JSON_NOTATION，JSONJAXBContext.JSONNotation.MAPPED）；
put（JSONJAXBContext.JSON_ROOT_UNWRAPPING，Boolean.TRUE）；
put（JSONJAXBContext.JSON_数组，jsonArray）；
this.types=newhashset您尝试过jersey json吗

将jersey json添加到类路径（或maven依赖项）

然后用这个：

@Provider
public class JAXBContextResolver implements ContextResolver<JAXBContext> {

    private final JAXBContext context;

    public JAXBContextResolver() throws Exception {
        this.context = new JSONJAXBContext(JSONConfiguration.natural().build(), "package.of.your.model");
    }

    public JAXBContext getContext(Class<?> objectType) {
        return context;
    }

}

查看本页的“改进应用程序”部分：

我知道这个问题很老，但我偶然发现了一个类似的问题，但我想呈现一个数组列表，即“列表”，因为我从jpa获得的一个db和一个不使用实体的nativ查询的结果

我就是这样解决的：

首先创建了ListWrapper.java：

import java.util.ArrayList;
import java.util.List;
import javax.xml.bind.annotation.XmlRootElement;

@XmlRootElement
public class ListWrapper extends ArrayList {

    @SuppressWarnings("unchecked")
    public ListWrapper() {
        super();
    }

    public ListWrapper(List list) {
        super(list);
    }
}

然后我创建了一个扩展AbstractMessageReaderWriterProvider的类

import org.codehaus.jettison.json.JSONArray;
import org.codehaus.jettison.json.JSONException;

import com.sun.jersey.core.provider.AbstractMessageReaderWriterProvider;

@Provider
@Produces("*/*")
@Consumes("*/*")
public class ListObjectArrayMessagereaderWriterProvider extends    AbstractMessageReaderWriterProvider<ListWrapper> {

    public boolean supports(Class type) {
        return type == ListWrapper.class;
    }

    @Override
    public boolean isReadable(Class<?> type, Type genericType, Annotation[] annotations, MediaType mediaType) {
        return type == ListWrapper.class;
    }

    @Override
    public ListWrapper readFrom(Class<ListWrapper> type, Type genericType, Annotation[] annotations, MediaType mediaType,
        MultivaluedMap<String, String> httpHeaders, InputStream entityStream) throws IOException, WebApplicationException {
        throw new IllegalArgumentException("Not implemented yet.");
    }

    @Override
    public boolean isWriteable(Class<?> type, Type genericType, Annotation[] annotations, MediaType mediaType) {
        return type == ListWrapper.class;
    }

    @SuppressWarnings("unchecked")
    @Override
    public void writeTo(ListWrapper t, Class<?> type, Type genericType, Annotation[] annotations, MediaType mediaType,
        MultivaluedMap<String, Object> httpHeaders, OutputStream entityStream) throws IOException, WebApplicationException {

        final Iterator<Object[]> iterator = t.iterator();

        OutputStreamWriter writer = new OutputStreamWriter(entityStream, getCharset(mediaType));
        final JSONArray jsonArrayOuter = new JSONArray();
        while (iterator.hasNext()) {
            final Object[] objs = iterator.next();
            JSONArray jsonArrayInner = new JSONArray(Arrays.asList(objs));
            jsonArrayOuter.put(jsonArrayInner);
        }
        try {
            jsonArrayOuter.write(writer);
            writer.write("\n");
            writer.flush();
        } catch (JSONException je) {
            throw new WebApplicationException(new Exception(ImplMessages.ERROR_WRITING_JSON_ARRAY(), je), 500);
        }
    }
}

搜索方法返回一个包含对象[]列表的Listwrapper

希望这对某人有所帮助：-）

import java.util.ArrayList;
import java.util.List;
import javax.xml.bind.annotation.XmlRootElement;

@XmlRootElement
public class ListWrapper extends ArrayList {

    @SuppressWarnings("unchecked")
    public ListWrapper() {
        super();
    }

    public ListWrapper(List list) {
        super(list);
    }
}

import org.codehaus.jettison.json.JSONArray;
import org.codehaus.jettison.json.JSONException;

import com.sun.jersey.core.provider.AbstractMessageReaderWriterProvider;

@Provider
@Produces("*/*")
@Consumes("*/*")
public class ListObjectArrayMessagereaderWriterProvider extends    AbstractMessageReaderWriterProvider<ListWrapper> {

    public boolean supports(Class type) {
        return type == ListWrapper.class;
    }

    @Override
    public boolean isReadable(Class<?> type, Type genericType, Annotation[] annotations, MediaType mediaType) {
        return type == ListWrapper.class;
    }

    @Override
    public ListWrapper readFrom(Class<ListWrapper> type, Type genericType, Annotation[] annotations, MediaType mediaType,
        MultivaluedMap<String, String> httpHeaders, InputStream entityStream) throws IOException, WebApplicationException {
        throw new IllegalArgumentException("Not implemented yet.");
    }

    @Override
    public boolean isWriteable(Class<?> type, Type genericType, Annotation[] annotations, MediaType mediaType) {
        return type == ListWrapper.class;
    }

    @SuppressWarnings("unchecked")
    @Override
    public void writeTo(ListWrapper t, Class<?> type, Type genericType, Annotation[] annotations, MediaType mediaType,
        MultivaluedMap<String, Object> httpHeaders, OutputStream entityStream) throws IOException, WebApplicationException {

        final Iterator<Object[]> iterator = t.iterator();

        OutputStreamWriter writer = new OutputStreamWriter(entityStream, getCharset(mediaType));
        final JSONArray jsonArrayOuter = new JSONArray();
        while (iterator.hasNext()) {
            final Object[] objs = iterator.next();
            JSONArray jsonArrayInner = new JSONArray(Arrays.asList(objs));
            jsonArrayOuter.put(jsonArrayInner);
        }
        try {
            jsonArrayOuter.write(writer);
            writer.write("\n");
            writer.flush();
        } catch (JSONException je) {
            throw new WebApplicationException(new Exception(ImplMessages.ERROR_WRITING_JSON_ARRAY(), je), 500);
        }
    }
}

    @GET
    @Path("/{id}/search")
    @Produces(JSON)
    public ListWrapper search(@PathParam("id") Integer projectId ) {
        return DatabaseManager.search(projectId);
    }