java - 使用 Jackson 处理器 spring mvc 3.1 的空指针异常

Question

我有下面的pojo，我正在尝试使用jackson处理器的spring支持来序列化和反序列化，下面是我的POJO类

public class Contract {
String term;
private List<Payment> paymentList=new ArrayList<Payment>();
public String getTerm() {
    return term;
}
public void setTerm(String term) {
    this.term = term;
}
public List<Payment> getPaymentList() {
    return paymentList;
}
public void setPaymentList(List<Payment> paymentList) {
    this.paymentList = paymentList;
}

}

在上面的类中，如果有一个列表，当我使用下面提到的 JUnit 测试用例时，我会收到空​​指针异常:

package com.budco.vsc.jsonmapping;

import static org.junit.Assert.assertEquals;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.nio.charset.Charset;

import org.codehaus.jackson.map.ObjectMapper;
import org.junit.Before;
import org.junit.Test;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.core.convert.ConversionService;
import org.springframework.format.support.FormattingConversionServiceFactoryBean;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpInputMessage;
import org.springframework.http.HttpOutputMessage;
import org.springframework.http.MediaType;
import org.springframework.http.converter.json.MappingJacksonHttpMessageConverter;
import org.springframework.samples.mvc.ajax.account.Contract;
import org.springframework.samples.mvc.ajax.json.ConversionServiceAwareObjectMapper;
import org.springframework.util.Assert;



 public class ContractJsonBindingTests{

Logger log = LoggerFactory.getLogger(ContractJsonBindingTests.class);

private MappingJacksonHttpMessageConverter converter;

private ObjectMapper objectMapper;


private String testPayload = "{\"term\":\"krish\"}";
@Before
public void setUp() {
    FormattingConversionServiceFactoryBean factoryBean = new FormattingConversionServiceFactoryBean();
    factoryBean.afterPropertiesSet();
    ConversionService conversionService = factoryBean.getObject();

    objectMapper = new ConversionServiceAwareObjectMapper(conversionService);
    converter = new MappingJacksonHttpMessageConverter();
    converter.setObjectMapper(objectMapper);
}

@Test
@SuppressWarnings("unchecked")
public void testAnnotationDrivenJsonConversion() throws Exception {
    MockHttpInputMessage inputMessage = new MockHttpInputMessage(testPayload.getBytes("UTF-8"));
    MediaType jsonType = new MediaType("application", "json");
    inputMessage.getHeaders().setContentType(jsonType);
    Contract contract = (Contract) converter.read((Class) Contract.class, inputMessage);
    Assert.notNull(contract);
    log.debug(contract.toString());

    MockHttpOutputMessage outputMessage = new MockHttpOutputMessage();
    converter.write(contract, jsonType, outputMessage);
    log.debug(outputMessage.getBody().toString());
    assertEquals("Incoming and outgoing JSON representations expected to match", testPayload, outputMessage.getBody().toString());
}

private static class MockHttpInputMessage implements HttpInputMessage {

    private final HttpHeaders headers = new HttpHeaders();

    private final InputStream body;

    public MockHttpInputMessage(byte[] contents) {
        Assert.notNull(contents, "'contents' must not be null");
        this.body = new ByteArrayInputStream(contents);
    }

    public HttpHeaders getHeaders() {
        return headers;
    }

    public InputStream getBody() throws IOException {
        return body;
    }
}

public class MockHttpOutputMessage implements HttpOutputMessage {

    private final HttpHeaders headers = new HttpHeaders();

    private final ByteArrayOutputStream body = new ByteArrayOutputStream();

    public HttpHeaders getHeaders() {
        return headers;
    }

    public OutputStream getBody() throws IOException {
        return body;
    }

    public byte[] getBodyAsBytes() {
        return body.toByteArray();
    }

    public String getBodyAsString(Charset charset) {
        byte[] bytes = getBodyAsBytes();
        return new String(bytes, charset);
    }
}
}

堆栈跟踪是

java.lang.NullPointerException
at org.springframework.samples.mvc.ajax.json.FormatAnnotationIntrospector.findDeserializer(FormatAnnotationIntrospector.java:33)
at org.codehaus.jackson.map.AnnotationIntrospector$Pair.findDeserializer(AnnotationIntrospector.java:1058)
at org.codehaus.jackson.map.deser.BasicDeserializerFactory.findDeserializerFromAnnotation(BasicDeserializerFactory.java:462)
at org.codehaus.jackson.map.deser.BeanDeserializerFactory.constructSettableProperty(BeanDeserializerFactory.java:606)
at org.codehaus.jackson.map.deser.BeanDeserializerFactory.addBeanProps(BeanDeserializerFactory.java:460)
at org.codehaus.jackson.map.deser.BeanDeserializerFactory.buildBeanDeserializer(BeanDeserializerFactory.java:149)
at org.codehaus.jackson.map.deser.BeanDeserializerFactory.createBeanDeserializer(BeanDeserializerFactory.java:116)
at org.codehaus.jackson.map.deser.StdDeserializerProvider._createDeserializer(StdDeserializerProvider.java:342)
at org.codehaus.jackson.map.deser.StdDeserializerProvider._createAndCache2(StdDeserializerProvider.java:264)
at org.codehaus.jackson.map.deser.StdDeserializerProvider._createAndCacheValueDeserializer(StdDeserializerProvider.java:244)
at org.codehaus.jackson.map.deser.StdDeserializerProvider.findValueDeserializer(StdDeserializerProvider.java:111)
at org.codehaus.jackson.map.deser.StdDeserializer.findDeserializer(StdDeserializer.java:482)
at org.codehaus.jackson.map.deser.BeanDeserializer.resolve(BeanDeserializer.java:271)
at org.codehaus.jackson.map.deser.StdDeserializerProvider._resolveDeserializer(StdDeserializerProvider.java:348)
at org.codehaus.jackson.map.deser.StdDeserializerProvider._createAndCache2(StdDeserializerProvider.java:303)
at org.codehaus.jackson.map.deser.StdDeserializerProvider._createAndCacheValueDeserializer(StdDeserializerProvider.java:244)
at org.codehaus.jackson.map.deser.StdDeserializerProvider.findValueDeserializer(StdDeserializerProvider.java:111)
at org.codehaus.jackson.map.deser.BasicDeserializerFactory.createCollectionDeserializer(BasicDeserializerFactory.java:182)
at org.codehaus.jackson.map.deser.StdDeserializerProvider._createDeserializer(StdDeserializerProvider.java:332)
at org.codehaus.jackson.map.deser.StdDeserializerProvider._createAndCache2(StdDeserializerProvider.java:264)
at org.codehaus.jackson.map.deser.StdDeserializerProvider._createAndCacheValueDeserializer(StdDeserializerProvider.java:244)
at org.codehaus.jackson.map.deser.StdDeserializerProvider.findValueDeserializer(StdDeserializerProvider.java:111)
at org.codehaus.jackson.map.deser.StdDeserializer.findDeserializer(StdDeserializer.java:482)
at org.codehaus.jackson.map.deser.BeanDeserializer.resolve(BeanDeserializer.java:271)
at org.codehaus.jackson.map.deser.StdDeserializerProvider._resolveDeserializer(StdDeserializerProvider.java:348)
at org.codehaus.jackson.map.deser.StdDeserializerProvider._createAndCache2(StdDeserializerProvider.java:303)
at org.codehaus.jackson.map.deser.StdDeserializerProvider._createAndCacheValueDeserializer(StdDeserializerProvider.java:244)
at org.codehaus.jackson.map.deser.StdDeserializerProvider.findValueDeserializer(StdDeserializerProvider.java:111)
at org.codehaus.jackson.map.deser.StdDeserializerProvider.findTypedValueDeserializer(StdDeserializerProvider.java:127)
at org.codehaus.jackson.map.ObjectMapper._findRootDeserializer(ObjectMapper.java:2046)
at org.codehaus.jackson.map.ObjectMapper._readMapAndClose(ObjectMapper.java:1980)
at org.codehaus.jackson.map.ObjectMapper.readValue(ObjectMapper.java:1331)
at org.springframework.http.converter.json.MappingJacksonHttpMessageConverter.readInternal(MappingJacksonHttpMessageConverter.java:124)
at org.springframework.http.converter.AbstractHttpMessageConverter.read(AbstractHttpMessageConverter.java:153)
at com.budco.vsc.jsonmapping.ContractJsonBindingTests.testAnnotationDrivenJsonConversion(ContractJsonBindingTests.java:59)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:601)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:44)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:41)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20)
at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:28)
at org.junit.runners.BlockJUnit4ClassRunner.runNotIgnored(BlockJUnit4ClassRunner.java:79)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:71)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:49)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:193)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:52)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:191)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:42)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:184)
at org.junit.runners.ParentRunner.run(ParentRunner.java:236)
at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50)
at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)

注意:- 如果我从 POJO 中删除列表属性( paymentList )，那么就没有问题。这意味着当 POJO 包含某些集合属性时，上述方法不起作用。如果有人有任何想法，请帮助我。

编辑:支付类别

public class Payment {

private BigDecimal amount;
private String payType;
private String transactionType;
private String chargeOrCancelFlag;
private String type;
private String authCode;
private Date authRequestDate;
private String authStatus;
private String authTransactioncode;
private SystemUser systemUser;
private String mailOrEmailInvoice;
private String monthlyBillOnDay;
private CreditCard creditCard;


public BigDecimal getAmount() {
    return amount;
}
public void setAmount(BigDecimal amount) {
    this.amount = amount;
}
public String getPayType() {
    return payType;
}
public void setPayType(String payType) {
    this.payType = payType;
}
public String getTransactionType() {
    return transactionType;
}
public void setTransactionType(String transactionType) {
    this.transactionType = transactionType;
}
public String getChargeOrCancelFlag() {
    return chargeOrCancelFlag;
}
public void setChargeOrCancelFlag(String chargeOrCancelFlag) {
    this.chargeOrCancelFlag = chargeOrCancelFlag;
}
public String getType() {
    return type;
}
public void setType(String type) {
    this.type = type;
}
public String getAuthCode() {
    return authCode;
}
public void setAuthCode(String authCode) {
    this.authCode = authCode;
}
public Date getAuthRequestDate() {
    return authRequestDate;
}
public void setAuthRequestDate(Date authRequestDate) {
    this.authRequestDate = authRequestDate;
}
public String getAuthStatus() {
    return authStatus;
}
public void setAuthStatus(String authStatus) {
    this.authStatus = authStatus;
}
public String getAuthTransactioncode() {
    return authTransactioncode;
}
public void setAuthTransactioncode(String authTransactioncode) {
    this.authTransactioncode = authTransactioncode;
}
public SystemUser getSystemUser() {
    return systemUser;
}
public void setSystemUser(SystemUser systemUser) {
    this.systemUser = systemUser;
}
public String getMailOrEmailInvoice() {
    return mailOrEmailInvoice;
}
public void setMailOrEmailInvoice(String mailOrEmailInvoice) {
    this.mailOrEmailInvoice = mailOrEmailInvoice;
}
public String getMonthlyBillOnDay() {
    return monthlyBillOnDay;
}
public void setMonthlyBillOnDay(String monthlyBillOnDay) {
    this.monthlyBillOnDay = monthlyBillOnDay;
}
public CreditCard getCreditCard() {
    return creditCard;
}
public void setCreditCard(CreditCard creditCard) {
    this.creditCard = creditCard;
}

 }

信用卡类别

   public class CreditCard {

private String type;
private String cardNumber;
private String name;
private String securityCode;
private String expirationDate;
private String firstFourDigit;
private String secondFourDigit;
private String thirdFourDigit;
private String lastFourDigits;
private String zipCode;



public void setMonth(String month){
    if(expirationDate==null)
        expirationDate=month;
    else
        expirationDate=month+"/"+expirationDate;
}

public void setYear(String year){
    if(expirationDate==null)
        expirationDate=year;
    else
        expirationDate=expirationDate+"/"+year;
}

public String getMonth() {
    return "";
}

public String getYear() {
    return "";
}

public String getType() {
    return type;
}

public void setType(String type) {
    this.type = type;
}

public String getCardNumber() {
    if (cardNumber == null)
        cardNumber = firstFourDigit + secondFourDigit + thirdFourDigit
                + lastFourDigits;
    return cardNumber;
}

public void setCardNumber(String cardNumber) {
    this.cardNumber = cardNumber;
}

public String getName() {
    return name;
}

public void setName(String name) {
    this.name = name;
}

public String getSecurityCode() {
    return securityCode;
}

public void setSecurityCode(String securityCode) {
    this.securityCode = securityCode;
}

public String getExpirationDate() {
    return expirationDate;
}

public void setExpirationDate(String expirationDate) {
    this.expirationDate = expirationDate;
}

public String getFirstFourDigit() {
    return firstFourDigit;
}

public String getSecondFourDigit() {
    return secondFourDigit;
}

public String getThirdFourDigit() {
    return thirdFourDigit;
}

public String getLastFourDigits() {
    return lastFourDigits;
}

public void setLastFourDigits(String lastFourDigits) {
    this.lastFourDigits = lastFourDigits;
}

public void setFirstFourDigit(String firstFourDigit) {
    this.firstFourDigit = firstFourDigit;
}

public void setSecondFourDigit(String secondFourDigit) {
    this.secondFourDigit = secondFourDigit;
}

public void setThirdFourDigit(String thirdFourDigit) {
    this.thirdFourDigit = thirdFourDigit;
}

public String getZipCode() {
    return zipCode;
}

public void setZipCode(String zipCode) {
    this.zipCode = zipCode;
}

  }

Answer 1

public void setMonth(String month){
    // ...
}

public void setYear(String year){
    // ...
}

问题出在这里。因为在自省(introspection)期间，spring 会查找名称为 setXXX 的名称的字段，而不是 set。

参见FormatAnnotationIntrospector source code

编辑(建议的解决方案):

public class CreditCard {
    public static class ExpirationDate {
        private String month;
        private String year;

        // getters, setter

        @Override
        public String toString() {
            return month + "/" + year;
        }
    }

    private String type;
    private String cardNumber;
    private String name;
    private String securityCode;
    private ExpirationDate expirationDate;
    private String firstFourDigit;
    private String secondFourDigit;
    private String thirdFourDigit;
    private String lastFourDigits;
    private String zipCode;

    public void setExpirationDate(ExpirationDate expDate){
        this.expirationDate = expDate;
    }

    public ExpirationDate getExpirationDate(){
        return this.expirationDate;
    }

    // other getters, setters
}