Jersey使用Gson作为Json Provider解析JSON

1. 首先实现相关接口

import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.UnsupportedEncodingException;
import java.lang.annotation.Annotation;
import java.lang.reflect.Type;

import javax.ws.rs.Consumes;
import javax.ws.rs.Produces;
import javax.ws.rs.WebApplicationException;
import javax.ws.rs.core.Application;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.MultivaluedMap;
import javax.ws.rs.ext.MessageBodyReader;
import javax.ws.rs.ext.MessageBodyWriter;
import javax.ws.rs.ext.Provider;

import cn.com.chaser.gasalarm.utils.IOUtils;

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;

@Provider
@Produces(MediaType.APPLICATION_JSON)
@Consumes(MediaType.APPLICATION_JSON)
public final class GsonJsonProvider implements MessageBodyWriter<Object>,
		MessageBodyReader<Object> {

	private static final String UTF_8 = "UTF-8";

	private Gson gson;

	private Gson getGson() {
		if (gson == null) {
			final GsonBuilder gsonBuilder = new GsonBuilder();
			gson = gsonBuilder.create();
		}
		return gson;
	}

	@Override
	public boolean isReadable(Class<?> type, Type genericType,
			java.lang.annotation.Annotation[] annotations, MediaType mediaType) {
		return true;
	}

	@Override
	public Object readFrom(Class<Object> type, Type genericType,
			Annotation[] annotations, MediaType mediaType,
			MultivaluedMap<String, String> httpHeaders, InputStream entityStream) {

		InputStreamReader streamReader = null;
		try {
			streamReader = new InputStreamReader(entityStream, UTF_8);
		} catch (UnsupportedEncodingException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		try {
			Type jsonType;
			if (type.equals(genericType)) {
				jsonType = type;
			} else {
				jsonType = genericType;
			}

			return getGson().fromJson(streamReader, jsonType);
		} finally {
			try {
				streamReader.close();
			} catch (IOException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}
	}

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

	@Override
	public long getSize(Object object, Class<?> type, Type genericType,
			Annotation[] annotations, MediaType mediaType) {
		return -1;
	}

	@Override
	public void writeTo(Object object, Class<?> type, Type genericType,
			Annotation[] annotations, MediaType mediaType,
			MultivaluedMap<String, Object> httpHeaders,
			OutputStream entityStream) throws IOException,
			WebApplicationException {
		OutputStreamWriter writer = new OutputStreamWriter(entityStream, UTF_8);
		try {
			Type jsonType;
			if (type.equals(genericType)) {
				jsonType = type;
			} else {
				jsonType = genericType;
			}
			getGson().toJson(object, jsonType, writer);
		} finally {
			writer.close();
		}
	}
}

2. 修改web.xml配置

<init-param>
			<param-name>resteasy.scan.providers</param-name>
			<param-value>true</param-value>
		</init-param>
		<init-param>
			<param-name>resteasy.use.builtin.providers</param-name>
			<param-value>false</param-value>
		</init-param>

3.读写JSON

	@GET
	@Path("/sysParams")
	@Produces(MediaType.APPLICATION_JSON)
	public SystemParameterRes getSystemParameters(
			@HeaderParam("tokenId") final String tokenId) {
		System.out.println("token:" + tokenId);
		SystemParameterRes o = new SystemParameterRes();
		o.setIntervalOfCheckMessage(300);
		o.setIntervalOfUpdateData(500);
		return o;
	}

@POST
	@Path("/login")
	@Consumes(MediaType.APPLICATION_JSON)
	@Produces(MediaType.APPLICATION_JSON)
	public LoginRes login(final User user) {
		// get the configuration
		CustomConfig.initConfig(sc);

		LoginRes o = new LoginRes();
		o.setName(user.getName());

		// check logged or not
		String userName = user.getName();
		Entry<String, UserToken> entry = TokenDao.checkUserToken(userName);
		if (entry != null) {
			o.setToken(entry.getKey());
		} else {
			// create a new token
			String token = IOUtils.generateToken(userName);
			System.out.println("token:" + token);

			UserToken userToken = new UserToken();
			userToken.setName(userName);
			userToken.setTimeout(System.currentTimeMillis());
			userToken.setToken(token);
			TokenDao.addToken(token, userToken);

			o.setToken(token);
		}
		return o;
	}

public class LoginRes {
	private String token;
	private String name;
	public String getToken() {
		return token;
	}
	public void setToken(String token) {
		this.token = token;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
}

public class UserToken {
	private String token;
	private String name;
	private long timeout;

	public String getToken() {
		return token;
	}

	public void setToken(String token) {
		this.token = token;
	}

	public String getName() {
		return name;
	}

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

	public long getTimeout() {
		return timeout;
	}

	public void setTimeout(long timeout) {
		this.timeout = timeout;
	}
}

public class User {

	private String name;

	private String password;

	public User() {

	}

	public String getName() {
		return name;
	}

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

	public String getPassword() {
		return password;
	}

	public void setPassword(String password) {
		this.password = password;
	}

}