Java解析JSON格式的数据封装到对应的Object中 - Google Gson的使用_JAVA_编程开发_程序员俱乐部

需求：

有一个JSON字符串数组："{\"serverMetrics\":[{\"vip\":\"caty1.vip.ebay.com\", \"metricsName\":\"CPU Number\", \"hostName\":\"caty1\", \"metricsTime\":\"20130101 13:22:15\", \"partitionKey\":\"00\", \"value\":\"1324\", \"thresholdParam1\":\"param1\", \"thresholdParam2\":\"param2\", \"thresholdParam3\":\"param3\", \"metricsP1\":\"p1\", \"metricsP2\":\"p2\", \"metricsP3\":\"p3\"}," +
??? ??? ??? ??? "{\"vip\":\"caty2.vip.ebay.com\", \"metricsName\":\"Memory\", \"hostName\":\"caty2\", \"metricsTime\":\"20130102 09:22:15\", \"partitionKey\":\"00\", \"value\":\"23456\", \"thresholdParam1\":\"param12\", \"thresholdParam2\":\"param22\", \"thresholdParam3\":\"param32\", \"metricsP1\":\"p12\", \"metricsP2\":\"p22\", \"metricsP3\":\"p32\"}," +
??? ??? ??? ??? "{\"vip\":\"caty3.vip.ebay.com\", \"metricsName\":\"Storage\", \"hostName\":\"caty3\", \"metricsTime\":\"20130103 19:22:15\", \"partitionKey\":\"00\", \"value\":\"56789\", \"thresholdParam1\":param13, \"thresholdParam23\":\"param2\", \"thresholdParam33\":\"param3\", \"metricsP13\":\"p1\", \"metricsP23\":\"p2\", \"metricsP33\":\"p3\"}" "]}";

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现在需要将该字符串封装到一个相应的Obejct中，考虑到Java中这类对象我们通常称为值传递对象（用来将传递的请求封装成相应的对象），我们可以创建相应的VO（Value Object), 将该VO命名为ServerMetricsVO

,而很容易看出，上面的Json格式的数据是一个数组，所以在ServerMetricsVO中会有一个List来对应此数组，于是我们再创建一个ServerMetricsItemVO,在ServerMetricsVO中有一个属性是List<ServerMetricsItemVO>. 为了体现Java的抽象编程，我们还创建了一个AbstractVO.最后创建一个Junit Class 来进行测试。

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一、AbtractVO

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class="java">public abstract class AbstractVO {
	/**
	 * Wrap the JSON format string to related VO object
	 * @param jsonString
	 * @return
	 */
	public abstract  AbstractVO fromGson(String jsonString);
}

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二、ServerMetricsVO

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public class ServerMetricsVO extends AbstractVO {

    /**
     * The property name must equal the property key name in returned JSON format
     */
    private List<ServerMetricsItemVO> serverMetrics;
   
    public ServerMetricsVO fromGson(String jsonString) {
        // Gson gson = new Gson(); // it will cause some Date parsed exception in some environment.
        Gson gson = new GsonBuilder().setDateFormat(DateUtils.MIDDLE_LINE_TIMESTAMP).create();
        ServerMetricsVO serverMetricsVO = gson.fromJson(jsonString, ServerMetricsVO.class);
        return serverMetricsVO;
    }

    public List<ServerMetricsItemVO> getServerMetrics() {
        return serverMetrics;
    }

    public void setServerMetrics(List<ServerMetricsItemVO> serverMetrics) {
        this.serverMetrics = serverMetrics;
    }
   
}

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三、ServerMetricsItemVO

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/**
 * This class is used to accept the JSON request and wrapped it to
 * the class
 * @author Josh Wang(Sheng)
 * 
 */
public class ServerMetricsItemVO {
	private String vip;
	
	private String metricsName;
	
	private String hostName;
	
	private Date metricsTime;
	
	private int partitionKey;
	
	private double value;
	
	private String thresholdParam1;
	
	private String thresholdParam2;
	
	private String thresholdParam3;
	
	private String metricsP1;
	
	private String metricsP2;
	
	private String metricsP3;
	
	/**
	 * table id used to decide to query source, will not persist into Database.
	 */
	private String tableId;

	public String getVip() {
		return vip;
	}

	public void setVip(String vip) {
		this.vip = vip;
	}

	public String getMetricsName() {
		return metricsName;
	}

	public void setMetricsName(String metricsName) {
		this.metricsName = metricsName;
	}

	public String getHostName() {
		return hostName;
	}

	public void setHostName(String hostName) {
		this.hostName = hostName;
	}

	public Date getMetricsTime() {
		return metricsTime;
	}

	public void setMetricsTime(Date metricsTime) {
		this.metricsTime = metricsTime;
	}

	public int getPartitionKey() {
		return partitionKey;
	}

	public void setPartitionKey(int partitionKey) {
		this.partitionKey = partitionKey;
	}

	public double getValue() {
		return value;
	}

	public void setValue(double value) {
		this.value = value;
	}

	public String getThresholdParam1() {
		return thresholdParam1;
	}

	public void setThresholdParam1(String thresholdParam1) {
		this.thresholdParam1 = thresholdParam1;
	}

	public String getThresholdParam2() {
		return thresholdParam2;
	}

	public void setThresholdParam2(String thresholdParam2) {
		this.thresholdParam2 = thresholdParam2;
	}

	public String getThresholdParam3() {
		return thresholdParam3;
	}

	public void setThresholdParam3(String thresholdParam3) {
		this.thresholdParam3 = thresholdParam3;
	}

	public String getMetricsP1() {
		return metricsP1;
	}

	public void setMetricsP1(String metricsP1) {
		this.metricsP1 = metricsP1;
	}

	public String getMetricsP2() {
		return metricsP2;
	}

	public void setMetricsP2(String metricsP2) {
		this.metricsP2 = metricsP2;
	}

	public String getMetricsP3() {
		return metricsP3;
	}

	public void setMetricsP3(String metricsP3) {
		this.metricsP3 = metricsP3;
	}

	public String getTableId() {
		return tableId;
	}

	public void setTableId(String tableId) {
		this.tableId = tableId;
	}
	
	
}

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四、TestVOConverterService

public class TestVOConverterService {

	private static IVOConverterService converterService;
	
	@BeforeClass
	public static void setUp() {
		converterService = (IVOConverterService)context.getBean("voConverterService");
	}
	
	@Test
	public void convert() {
		String jsonString = "{\"serverMetrics\":[{\"vip\":\"caty1.vip.ebay.com\", \"metricsName\":\"CPU Number\", \"hostName\":\"caty1\", \"metricsTime\":\"20130101 13:22:15\", \"partitionKey\":\"00\", \"value\":\"1324\", \"thresholdParam1\":\"param1\", \"thresholdParam2\":\"param2\", \"thresholdParam3\":\"param3\", \"metricsP1\":\"p1\", \"metricsP2\":\"p2\", \"metricsP3\":\"p3\"}," +
				"{\"vip\":\"caty2.vip.ebay.com\", \"metricsName\":\"Memory\", \"hostName\":\"caty2\", \"metricsTime\":\"20130102 09:22:15\", \"partitionKey\":\"00\", \"value\":\"23456\", \"thresholdParam1\":\"param12\", \"thresholdParam2\":\"param22\", \"thresholdParam3\":\"param32\", \"metricsP1\":\"p12\", \"metricsP2\":\"p22\", \"metricsP3\":\"p32\"}," +
				"{\"vip\":\"caty3.vip.ebay.com\", \"metricsName\":\"Storage\", \"hostName\":\"caty3\", \"metricsTime\":\"20130103 19:22:15\", \"partitionKey\":\"00\", \"value\":\"56789\", \"thresholdParam1\":param13, \"thresholdParam23\":\"param2\", \"thresholdParam33\":\"param3\", \"metricsP13\":\"p1\", \"metricsP23\":\"p2\", \"metricsP33\":\"p3\"}" +
				"]}";
//		String jsonString = "{\"serverMetrics\":[{\"vip\":\"caty1.vip.ebay.com\", \"metricsName\":\"CPU Number\", \"hostName\":\"caty1\", \"metricsTime\":\"2013-01-01 13:22:15\", \"partitionKey\":\"00\", \"value\":\"1324\", \"thresholdParam1\":\"param1\", \"thresholdParam2\":\"param2\", \"thresholdParam3\":\"param3\", \"metricsP1\":\"p1\", \"metricsP2\":\"p2\", \"metricsP3\":\"p3\"}]}";
		AbstractVO vo = new ServerMetricsVO();
		ServerMetricsVO metricsVO = (ServerMetricsVO)converterService.convert(vo, jsonString);
		for (ServerMetricsItemVO item : metricsVO.getServerMetrics()) {
			print(item.getVip() + "   " + item.getHostName() + "  " + item.getMetricsName() + "  " + item.getPartitionKey());
		}
	}
}

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从上面的代码可以看出，用Goole的Gson类来做这个操作，那可是相当的简单，只需要构造一个Gson对象，传入一个json字符串和想要转换到的目标Object类即可完成转换。当然转换的时候一定要注意传入的json字符串是有效的json字符串。

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