| The traditional Geographic Information System (GIS) based on the structure of Client / Server could not afford openness, security and diversity in the environment of Internet. Meanwhile, it means a huge potential for advance. The new generation of GIS is different from the traditional one at aspects of composing structure and applied technology. Web GIS appears along with the progress of Web technology. It has been a critical trend for the development of international GIS that Browser / Server based Web GIS takes full advantage of Web resources to provide wider range of geographic services for people through modern net infrastructure. Java is a general solution which features cross platform, robustness, security and high performance. It is ideal for Internet oriented programming.This thesis brings forward a Web GIS construction pattern after investigation and analysis of some application modes and realization approaches. A prototype system is built to research some key technologies of Java-based Web GIS. The whole system can be divided into 3 tiers, including client tier, Web tier and data tier. The client tier is a interface between user and system. The Web tier is based on Java servlet. It receives commands from client tier and gets data from data tier. After processing, it sends results back to the client tier. The data tier restores all data and sends data to Web tier according to query directives. The data preprocessing is also important. We deal with data in different ways based on different characteristics of data to adapt them to concurrent accessing and net transmission.The design of the prototype system embodies superiority of Java technology in building of Web GIS. The system satisfies design requirements proved by testing. It makes beneficial exploration for the realization of Internet GIS. |
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