首先，您的列表注释缺少条目名称：
@ElementList(inline = true, required = false, entry = 'object')private List<Object> params;
否则<string>...</string>，不使用<object>...</object>。您可以通过添加type = String.class到列表的注释中来防止空指针异常。但是，这不能解决主要问题。
通常，空标记/- null元素不会添加到结果中。
这是一个使用来解决此问题的示例Converter。
public class SimpleframeworkTest{ // ... @Root(name = 'container', strict = false) @Convert(NullawareContainerConverter.class) public static class Container {static final Serializer ser = new Persister(new AnnotationStrategy());// ...public String toXml() throws Exception{ StringWriter sw = new StringWriter(); ser.write(this, sw); return sw.toString();}public static Container toObject(String xml) throws Exception{ return ser.read(Container.class, xml);}// ... } static class NullawareContainerConverter implements Converter<Container> {final Serializer ser = new Persister();@Overridepublic Container read(InputNode node) throws Exception{ final Container c = new Container(); c.id = Integer.valueOf(node.getAttribute('id').getValue()); c.params = new ArrayList<>(); InputNode n; while( ( n = node.getNext('object')) != null ) {/* * If the value is null it’s added too. You also can add some * kind of null-replacement element here too. */c.params.add(n.getValue()); } return c;}@Overridepublic void write(OutputNode node, Container value) throws Exception{ ser.write(value.id, node); for( Object obj : value.params ) {if( obj == null ){ obj = ''; // Set a valid value if null}// Possible you have to tweak this by handser.write(obj, node); }} }}
如评论中所写，您必须做一些进一步的工作。
testNullsInParams（）
<container> <integer>4000</integer> <string>foo</string> <string></string> <string>bar</string></container>
testDeserializeNull（）
Container [id=4000, params=[foo, null, bar]]解决方法
我必须支持的一个项目中有一个对象->XML->对象过程。该对象包含List，并且如果将其序列化，则会省略list中存在的所有空值。我的问题是，可以使用Simpleframework完成还是应该使用其他方法？什么？这是我的工作：
import java.io.StringWriter;import java.util.Arrays;import java.util.List;import org.simpleframework.xml.Attribute;import org.simpleframework.xml.ElementList;import org.simpleframework.xml.Root;import org.simpleframework.xml.core.Persister;import org.testng.annotations.Test;public class SimpleframeworkTest { @Test public void testNullsInParams() throws Exception {Container container = new Container();container.setId(4000);container.setParams(Arrays.asList(new Object[] { 'foo',null,'bar' }));String xml = container.toXml(); // omits null value in output } @Test public void testDeserializeNull() throws Exception {String xml = '<container id='4000'>'+' <object class='java.lang.String'>foo</object>'+// ' <object class='java.lang.String'></object>'+ // gets NullPointerException here' <object class='java.lang.String'>bar</object>'+'</container>';Container object = Container.toObject(xml); } @Root(name = 'container',strict = false) public static class Container {@Attributeprivate Integer id;@ElementList(inline = true,required = false)private List<Object> params;public String toXml() throws Exception { StringWriter sw = new StringWriter(); new Persister().write(this,sw); return sw.toString();}public static Container toObject(String xml) throws Exception { return new Persister().read(Container.class,xml);}public Integer getId() { return id;}public void setId(Integer id) { this.id = id;}public List<Object> getParams() { return params;}public void setParams(List<Object> params) { this.params = params;}@Overridepublic String toString() { return 'Container [id=' + id + ',params=' + params + ']';} }}
