Json字符串和Java对象转换利器——Jackson

Maven配置：

<dependency><groupId>com.fasterxml.jackson.core</groupId><artifactId>jackson-databind</artifactId><version>2.1.3</version></dependency>

实体类GetOrdersResponse：

package org.jackson.jsontest.po;import java.util.List; /** * Generated by FreeMarker * */public class GetOrdersResponse  {    /********** attribute ***********/    private String timestamp;    private String ack;    private String version;    private String build;        private PaginationResult paginationResult;    private List<Order> orderArray;      /********** get/set ***********/    public String getTimestamp() {        return timestamp;    }     public void setTimestamp(String timestamp) {        this.timestamp = timestamp;    }    public String getAck() {        return ack;    }     public void setAck(String ack) {        this.ack = ack;    }    public String getVersion() {        return version;    }     public void setVersion(String version) {        this.version = version;    }    public String getBuild() {        return build;    }     public void setBuild(String build) {        this.build = build;    }public List<Order> getOrderArray() {return orderArray;}public void setOrderArray(List<Order> orderArray) {this.orderArray = orderArray;}public PaginationResult getPaginationResult() {return paginationResult;}public void setPaginationResult(PaginationResult paginationResult) {this.paginationResult = paginationResult;}@Overridepublic String toString() {return "GetOrdersResponse [ack=" + ack + ", build=" + build+ ", orderArray=" + orderArray + ", paginationResult="+ paginationResult + ", timestamp=" + timestamp + ", version="+ version + "]";}}

实体类Order：

package org.jackson.jsontest.po;import org.jackson.jsontest.po.order.CheckoutStatus; /** * Generated by FreeMarker * */public class Order  {    /********** attribute ***********/    private String orderID;    private CheckoutStatus checkoutStatus;    private String buyerUserID;      /********** get/set ***********/    public String getOrderID() {        return orderID;    }     public void setOrderID(String orderID) {        this.orderID = orderID;    }        public CheckoutStatus getCheckoutStatus() {        return checkoutStatus;    }     public void setCheckoutStatus(CheckoutStatus checkoutStatus) {        this.checkoutStatus = checkoutStatus;    }    public String getBuyerUserID() {        return buyerUserID;    }     public void setBuyerUserID(String buyerUserID) {        this.buyerUserID = buyerUserID;    }@Overridepublic String toString() {return "Order [buyerUserID=" + buyerUserID + ", checkoutStatus="+ checkoutStatus + ", orderID=" + orderID + "]";}  }

实体类PaginationResult：

package org.jackson.jsontest.po; /** * Generated by FreeMarker * */public class PaginationResult  {    /********** attribute ***********/    private String totalNumberOfEntries;    private String totalNumberOfPages;      /********** get/set ***********/    public String getTotalNumberOfEntries() {        return totalNumberOfEntries;    }     public void setTotalNumberOfEntries(String totalNumberOfEntries) {        this.totalNumberOfEntries = totalNumberOfEntries;    }    public String getTotalNumberOfPages() {        return totalNumberOfPages;    }     public void setTotalNumberOfPages(String totalNumberOfPages) {        this.totalNumberOfPages = totalNumberOfPages;    }@Overridepublic String toString() {return "PaginationResult [totalNumberOfEntries=" + totalNumberOfEntries+ ", totalNumberOfPages=" + totalNumberOfPages + "]";}  }

实体类CheckoutStatus：

package org.jackson.jsontest.po.order; /** * Generated by FreeMarker * */public class CheckoutStatus  {    /********** attribute ***********/    private String eBayPaymentStatus;    private String lastModifiedTime;    private String status;      /********** get/set ***********/    public String getEBayPaymentStatus() {        return eBayPaymentStatus;    }     public void setEBayPaymentStatus(String eBayPaymentStatus) {        this.eBayPaymentStatus = eBayPaymentStatus;    }    public String getLastModifiedTime() {        return lastModifiedTime;    }     public void setLastModifiedTime(String lastModifiedTime) {        this.lastModifiedTime = lastModifiedTime;    }    public String getStatus() {        return status;    }     public void setStatus(String status) {        this.status = status;    }@Overridepublic String toString() {return "CheckoutStatus [eBayPaymentStatus=" + eBayPaymentStatus+ ", lastModifiedTime=" + lastModifiedTime + ", status="+ status + "]";}}

工具类JackSon：

package org.jackson.jsontest;import com.fasterxml.jackson.databind.ObjectMapper;public class JackSon {/** * Json字符串转对象 * @param <T> * @param jsonStr * @param clazz * @return * @throws Exception */public <T> T jsonStrToBean(String jsonStr, Class<T> clazz) throws Exception {ObjectMapper mapper = new ObjectMapper();return mapper.readValue(jsonStr, clazz);}/** * 对象转Json字符串 * @param bean * @return * @throws Exception */public String beanToJsonStr(Object bean) throws Exception {ObjectMapper mapper = new ObjectMapper();return mapper.writeValueAsString(bean);}}

测试类JackSonTest：

package org.jackson.jsontest;import java.io.IOException;import java.util.ArrayList;import java.util.List;import org.jackson.jsontest.po.GetOrdersResponse;import org.jackson.jsontest.po.Order;import org.jackson.jsontest.po.PaginationResult;import org.jackson.jsontest.po.order.CheckoutStatus;import org.junit.Before;import org.junit.Test;public class JackSonTest {JackSon jackSon;static GetOrdersResponse ordersResponse;static String jsonStr;@Beforepublic void before(){jackSon= new JackSon();}static {ordersResponse = new GetOrdersResponse();ordersResponse.setTimestamp("2007-12-10T16:12:55.184Z");ordersResponse.setAck("Success");ordersResponse.setBuild("e539_core_Bundled_5642307_R1");ordersResponse.setVersion("539");List<Order> orders = new ArrayList<Order>();for (int i = 0; i < 3; i++) {Order order = new Order();order.setOrderID("OrderId_" + i);order.setBuyerUserID("BuyerUserId_" + i);CheckoutStatus checkoutStatus = new CheckoutStatus();checkoutStatus.setEBayPaymentStatus("EBayPaymentStatus_" + i);checkoutStatus.setLastModifiedTime("LastModifiedTime_" + i);checkoutStatus.setStatus("Status_" + i);order.setCheckoutStatus(checkoutStatus);orders.add(order);}ordersResponse.setOrderArray(orders);PaginationResult paginationResult = new PaginationResult();paginationResult.setTotalNumberOfEntries("10");paginationResult.setTotalNumberOfPages("5");ordersResponse.setPaginationResult(paginationResult);}@Testpublic void testBeanToJsonStr() {try {jsonStr = jackSon.beanToJsonStr(ordersResponse);System.out.println(jsonStr);} catch (Exception e) {e.printStackTrace();}}@Testpublic void testJsonStrToBean() {try {GetOrdersResponse ordersResponse = jackSon.jsonStrToBean(jsonStr, GetOrdersResponse.class);System.out.println(ordersResponse);} catch (IOException e) {e.printStackTrace();} catch (Exception e) {e.printStackTrace();}}}

结果：

-----------Java对象转Json字符串结果------------{"timestamp":"2007-12-10T16:12:55.184Z","ack":"Success","version":"539","build":"e539_core_Bundled_5642307_R1","paginationResult":{"totalNumberOfEntries":"10","totalNumberOfPages":"5"},"orderArray":[{"orderID":"OrderId_0","checkoutStatus":{"lastModifiedTime":"LastModifiedTime_0","status":"Status_0","ebayPaymentStatus":"EBayPaymentStatus_0"},"buyerUserID":"BuyerUserId_0"},{"orderID":"OrderId_1","checkoutStatus":{"lastModifiedTime":"LastModifiedTime_1","status":"Status_1","ebayPaymentStatus":"EBayPaymentStatus_1"},"buyerUserID":"BuyerUserId_1"},{"orderID":"OrderId_2","checkoutStatus":{"lastModifiedTime":"LastModifiedTime_2","status":"Status_2","ebayPaymentStatus":"EBayPaymentStatus_2"},"buyerUserID":"BuyerUserId_2"}]}-----------Json字符串转Java对象结果------------GetOrdersResponse [ack=Success, build=e539_core_Bundled_5642307_R1, orderArray=[Order [buyerUserID=BuyerUserId_0, checkoutStatus=CheckoutStatus [eBayPaymentStatus=EBayPaymentStatus_0, lastModifiedTime=LastModifiedTime_0, status=Status_0], orderID=OrderId_0], Order [buyerUserID=BuyerUserId_1, checkoutStatus=CheckoutStatus [eBayPaymentStatus=EBayPaymentStatus_1, lastModifiedTime=LastModifiedTime_1, status=Status_1], orderID=OrderId_1], Order [buyerUserID=BuyerUserId_2, checkoutStatus=CheckoutStatus [eBayPaymentStatus=EBayPaymentStatus_2, lastModifiedTime=LastModifiedTime_2, status=Status_2], orderID=OrderId_2]], paginationResult=PaginationResult [totalNumberOfEntries=10, totalNumberOfPages=5], timestamp=2007-12-10T16:12:55.184Z, version=539]

需要注意的是，在反序列化时（Json字符串转Java对象），如果Json字符串有冗余（Json属性在Java对象中找不到对应的字段），则会抛出UnrecognizedPropertyException异常，此时可以设置以下属性：

objectMapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);